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			1	.. _common-3dr-radio-advanced-configuration-and-technical-information:
			2
			3	==================================
			4	SiK Radio — Advanced Configuration
			5	==================================
			6
			7	This article provides advanced configuration information for the
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			8	:ref:`SiK Telemetry Radio <common-sik-telemetry-radio>`. It is intended for
			9	"power users", and those who wish to gain a better understanding of how
			10	the radios operate.
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			11
			12	.. tip::
			13
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			14	Most users will only need the basic guide and feature overview
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			15	provided in :ref:`SiK Radio v2 <common-sik-telemetry-radio>`.
			16
			17	.. image:: ../../../images/Telemetry_Ver1Ver2.jpg
			18	:target: ../_images/Telemetry_Ver1Ver2.jpg
			19
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			20	Monitoring the link quality
			21	===========================
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			23	You can use the MAVLink support in the SiK Radios to monitor the link
			24	quality while flying, if your ground station supports it.
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			26	The two key message parameters are ``RADIO.rssi`` and ``RADIO.remrssi``.
			27	The first is the RSSI (signal strength) level that the local radio is
			28	receiving at. The remrssi parameter is the RSSI that the remote radio is
			29	receiving at.
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			31	Here is a typical graph of the RSSI levels for a flight at my local
			32	flying field.
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			33
			34	.. image:: ../../../images/rssi-distance.jpg
			35	:target: ../_images/rssi-distance.jpg
			36
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			37	The RSSI value scales approximately as 1.9x the dBm signal strength,
			38	plus an offset. See the Si1000 data sheet for the exact mapping between
			39	RSSI and dBm received signal strength, or use this approximate formula
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			41	::
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			43	signal_dBm = (RSSI / 1.9) - 127
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			44
			45	.. note::
			46
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			47	The reason the RSSI varies so much during this flight is that the
			48	signal is attenuated when the plane is rolled over in a turn as I was
			49	using a simple wire antenna in the plane. The RSSI values for this
			50	flight were plenty high enough for the link quality to be excellent
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			51	throughout the flight using the default radio parameters.
			52
			53	.. _common-3dr-radio-advanced-configuration-and-technical-information_diagnosing_range_problems:
			54
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			55	Diagnosing range problems
			56	=========================
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			58	If you get less range than you would expect from the above information
			59	then what you need to do is graph the noise and signal levels from a
			60	flight to work out what the problem is.
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			62	The most common source of range problems is noise. Noise is unwanted
			63	radio emissions in the same frequency range that your radio is using
			64	that interferes with the operation of your radio. The radios have
			65	telemetry logging built in to help you diagnose the source of the noise.
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			67	There are three key types of noise that are likely to affect your
			68	radios:
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			70	- Noise from the electronics in your aircraft (such as your motor, ESC,
			71	APM etc)
			72	- Noise from your ground station computer, especially its USB bus
			73	- Noise from other people operating radios nearby that are on the same
			74	frequency as your radios
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			76	To work out what sort of noise you have, open up mission planner and
			77	choose the "telemetry logs" tab. Then choose Tlog> Kml or Graph.
			78	When the window pops up choose Graph Log and select a log from a
			79	test flight with your radios. Wait for the log to load, then choose the
			80	following items to log:
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			82	- rssi
			83	- remrssi
			84	- noise
			85	- remnoise
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			87	Put all 4 values on the one graph. You will end up with a plot like
			88	this:
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			89
			90	.. image:: ../../../images/diag-range-graph1.png
			91	:target: ../_images/diag-range-graph1.png
			92
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			93	That graph shows you 4 things:
			94
			95	- the amount of signal being received on the ground
			96	- the amount of signal being received in the aircraft
			97	- the amount of noise being received on the ground
			98	- the amount of noise being received in the aircraft
			99
			100	For the best possible range you want the two noise lines to be low, and
			101	the two signal lines to be high. In the above graph (taken from my
			102	SkyFun with a pair of 3DR 433 radios) you can see that the noise levels
			103	in the plane are higher than the noise levels on the ground. Also note
			104	that at the start of the flight (before I started the motor) the noise
			105	levels on the plane were lower, then they went up after I started the
			106	motor. That shows I'm getting some noise from my motor. If I wanted more
			107	range I would need to move the radio further from the motor and ESC.
			108
			109	Perhaps the most common source of noise with the 3DR-433 is noise from
			110	the USB bus on your ground station. That shows up as high values for the
			111	RADIO.noise value. If you get this, then you could try using a different
			112	USB cable, or a different laptop. You can also try using a USB hub
			113	between your laptop and your radio.
			114
			115	If the 'rssi' and 'noise' levels meet on the graph then you will lose
			116	the link. To determine what your range would be, a rough rule of thumb
			117	is to subtract the 'rssi' and 'noise' numbers, then divide by 2. That
			118	tells you your "fade margin" in decibels. For each 6dB of fade margin
			119	your range doubles. So if you have 18dB of fade margin, then you will be
			120	able to do roughly 8x whatever range you were at when you measured the
			121	margin.
			122
			123	Another key source of range problems is the antenna placement. Your
			124	ground station antenna should be well clear of obstructions and a couple
			125	of meters off the ground. You may need to build a stand to hold it to
			126	get the best range.
			127
			128	Serial and air rates 'one byte form'
			129	====================================
			130
			131	The ``SERIAL_SPEED`` and ``AIR_SPEED`` parameters are in the same form
			132	that APM uses for the ``SERIAL3_SPEED`` EEPROM parameter. It is the rate
			133	in kbps, truncated to an integer. So '9' means 9600 baud, '38' means
			134	38400, '115' means 115200 etc.
			135
			136	Choosing the air data rate
			137	==========================
			138
			139	The key parameter that controls the range of your radios is the
			140	``AIR_SPEED``. The default is 64 (which is 64kbps) will give you a range
			141	of over a kilometre with small omni antennas. The lower you set the
			142	``AIR_SPEED`` the longer your range, although lowering the ``AIR_SPEED``
			143	also lowers how much data you can send over the link.
			144
			145	The radio firmware can only support 13 possible air date rates, which
			146	are 2, 4, 8, 16, 19, 24, 32, 48, 64, 96, 128, 192 and 250. If your
			147	application needs a different air rate for some reason then we can
			148	potentially add it to the register tables. If you choose an unsupported
			149	air rate then the next highest rate from the supported list will be
			150	chosen.
			151
			152	What air data rate you choose will depend on the following factors:
			153
			154	- What range you need
			155	- What data rate you will be sending
	156	- Whether you primarily send in one direction, or both
	157	- Whether you have ECC enabled
	158	- Whether you have an APM firmware with adaptive flow control
	159
	160	For most telemetry applications you will primarily be sending data
	161	mostly in one direction, from the aircraft to the ground station. For
	162	most people, the amount of data sent from the ground station to the
	163	aircraft is small, just an occasional control packet plus heartbeat
	164	packets.
	165
	166	If you are using a joystick to control your aircraft then you will be
	167	sending a lot more data from the ground station to the aircraft, and in
	168	that case you may find a higher ``AIR_SPEED`` is needed, although your
	169	range will be reduced.
	170
	171	The ``ECC`` parameter makes a big difference to the data rate you can
	172	support at a given ``AIR_SPEED``. If you have ECC set to zero, then no
	173	error correcting information is sent, and the radio uses a simple 16 bit
	174	CRC to detect transmission errors. In that case your radio will be able
	175	to support data transfers in one direction of around 90% of the
	176	``AIR_SPEED``.
	177
	178	If you enable ECC (which is highly recommended), then the data rate you
	179	can support is halved. The ECC system doubles the size of the data sent
	180	by the radios. It is worth it however, as the bit error rate will drop
	181	dramatically, and you are likely to get a much more reliable link at
	182	longer ranges.
	183
	184	If you have the latest APM firmware (Plane 2.33 or later, or Copter 2.54
	185	or later) then the APM will automatically adapt its telemetry rates to
	186	what the radio can handle, by using MAVLink RADIO packets injected into
	187	the MAVLink streams by the radios firmware. That allows you to
	188	'oversubscribe' your link, by setting up a ``SERIAL_SPEED`` larger than
	189	what the radios can actually handle.
	190
	191	The other factor in choosing the air data rate is the TDM 'sync time'.
	192	The two radios need to work out each others frequency hopping pattern.
	193	They do this by slowly changing the receive channel while rapidly
	194	changing the transmit channel. This process of getting in sync with the
	195	other radio takes just a few seconds at high air data rates, but gets
	196	slower for low air data rates.
	197
	198	For most amateur UAV applications the default ``AIR_SPEED`` of 64 with
	199	ECC enabled will be good.
	200
	201	Error correction
	202	================
	203
	204	As mentioned above, the radios support a 12/24 Golay error correcting
	205	code if you set the ECC parameter to 1. This means that for every 12
	206	bits of data the radio will send 24 bits, calculating the bits using
	207	Golay code lookup tables. The process is reversed on the receiving end,
	208	and allows the radio to correct bit errors of up to 3 bits in every 12
	209	bits send (i.e. 25% bit error rate).
	210
	211	The downside of the ECC option is that it halves your available data
	212	bandwidth, but in most cases this is worth it, as you are able to
	213	sustain a reliable link over longer ranges. You will also get a lot less
	214	'noise' in the serial stream.
	215
	216	MAVLink framing
	217	===============
	218
	219	If you set the MAVLINK option to 1 or 2 then the radio will do 'MAVLink
	220	framing'. The MAVLink protocol is used by APM for transmitting telemetry
	221	date to a ground station. When MAVLink framing is used, the radio will
	222	try to align radio packets with MAVLink packet boundaries. This means
	223	that if a packet is lost you don't end up with half a MAVLink packet
	224	being seen by the receiver. That partial packet would appear as line
	225	noise on your ground stations console.
	226
	227	If you set MAVLINK to 2, then in addition to doing MAVLink framing the
	228	radio will look for ``RC_OVERRIDE`` packets (used for joysticks) and
	229	ensure that those packets get sent as quickly as possible. This option
	230	is useful if you are using a tablet based joystick for control.
	231
	232	The radio firmware will try to fit multiple MAVLink packets into one
	233	radio packet where possible for maximum efficiency. The highest radio
	234	packet size is 252 bytes.
	235
	236	The radio firmware supports both the MAVLink 0.9 and the MAVLink 1.0
	237	transmission formats.
	238
	239	MAVLink reporting
	240	=================
	241
	242	If you have MAVLINK set to 1, then the radio firmware will also look for
	243	MAVLink HEARTBEAT messages coming from the serial connection. If it sees
	244	a HEARTBEAT message then it knows that the MAVLink protocol is in use,
	245	and it will start injecting MAVLink 'RADIO' status packets into the the
	246	serial stream.
	247
	248	The RADIO packets contain information about the RSSI (Received Signal
	249	Strength Indicator) level at both ends of the link, allowing the ground
	250	station or aircraft to take action in case the link quality falls too
	251	low.
	252
	253	The RADIO packets also contain information about error rates, and how
	254	full the serial transmit buffer is (as a percentage). The latest APM
	255	firmware can use this information to automatically adapt the telemetry
	256	stream rates to the data rate that the radios can sustain.
	257
	258	Power levels
	259	============
	260
	261	You need to be very careful to configure your radios to stay within the
	262	legal power limits of the country you are operating in. The default
	263	power level of 20dBm is fine for the US and Australia, as up to 30dBm is
	264	allowed by the LIPD class licenses there in the 915-928MHz frequency
	265	band for a frequency hopping radio. So as long as your antennas have a
	266	gain of less than 10dBi you should be within the ISM rules.
	267
	268	The radio cannot support arbitrary power levels. It can only support the
	269	power levels given in the following table
	270
	271	.. raw:: html
	272
	273	<table>
	274	<tbody>
	275	<tr>
	276	<th>Power (dBm)</th>
	277	<th>Power (milliWatts)</th>
	278	</tr>
	279	<tr>
	280	<td>1</td>
	281	<td>1.3</td>
	282	</tr>
	283	<tr>
	284	<td>2</td>
	285	<td>1.6</td>
	286	</tr>
	287	<tr>
	288	<td>5</td>
	289	<td>3.2</td>
	290	</tr>
	291	<tr>
	292	<td>8</td>
	293	<td>6.3</td>
	294	</tr>
	295	<tr>
	296	<td>11</td>
	297	<td>12.5</td>
	298	</tr>
	299	<tr>
	300	<td>14</td>
	301	<td>25</td>
	302	</tr>
	303	<tr>
	304	<td>17</td>
	305	<td>50</td>
	306	</tr>
	307	<tr>
	308	<td>20</td>
	309	<td>100</td>
	310	</tr>
	311	</tbody>
	312	</table>
	313
	314	If you choose an unsupported power level the radio will choose the next
	315	highest power level from the above table.
	316
	317	Please carefully check the EIRP (Equivalent isotropically radiated
	318	power) power limits for your country, making sure you take into account
	319	the antenna gain. The radio is a 'DIY' radio part and it is entirely
	320	your responsibility to ensure any use of it is compliant with local
	321	rules.
	322
	323	For example, if your local rules allow for a maximum of 30dBm (1W) EIRP,
	324	then if you use a amplifier with a 12dB transmit gain, and an antenna
	325	with 3dBi gain, then you will need to set TXPOWER to at most 14.
	326
	327	If you don't know how to calculate it, we've made a tutorial for you
	328	here: :ref:`Understanding dB, Watts and dBm <common-antenna-design_understanding_db_watts_and_dbm>`.
	329
	330	Using the AT command set
	331	========================
	332
	333	The radios support a variant of the Hayes 'AT' modem command set for
	334	configuration.
	335
	336	If you connect with a serial console to a radio at the current serial
	337	baud rate, you can tell the radio to enter AT command mode by entering
	338	the sequence '+++'. To prevent data being seen as the command sequence
	339	there is a guard time required, so make sure you type nothing on the
	340	serial link for 1 second before and after you enter the sequence.
	341
	342	When you enter AT command mode you will receive a 'OK' prompt from the
	343	radio and it will stop displaying data sent from the other radio.
	344
	345	Once in AT command mode, you can give the radio either 'AT' commands to
	346	control the local radio, or (if successfully connected) you can use 'RT'
	347	commands to control the remote radio.
	348
	349	The AT commands available are:
	350
	351	- ATI - show radio version
	352	- ATI2 - show board type
	353	- ATI3 - show board frequency
	354	- ATI4 - show board version
	355	- ATI5 - show all user settable EEPROM parameters
	356	- ATI6 - display TDM timing report
	357	- ATI7 - display RSSI signal report
	358	- ATO - exit AT command mode
	359	- ATSn? - display radio parameter number 'n'
	360	- ATSn=X - set radio parameter number 'n' to 'X'
	361	- ATZ - reboot the radio
	362	- AT&W - write current parameters to EEPROM
	363	- AT&F - reset all parameters to factory default
	364	- AT&T=RSSI - enable RSSI debug reporting
	365	- AT&T=TDM - enable TDM debug reporting
	366	- AT&T - disable debug reporting
	367
	368	all of these commands, except for ATO, may be used on a connected remote
	369	radio by replacing 'AT' with 'RT'.
	370
	371	Perhaps the most useful command is 'ATI5' which displays all user
	372	settable EEPROM parameters. That will produce a report like this:
	373
	374	::
	375
	376	S0: FORMAT=22
	377	S1: SERIAL_SPEED=57
	378	S2: AIR_SPEED=64
	379	S3: NETID=25
	380	S4: TXPOWER=20
	381	S5: ECC=1
	382	S6: MAVLINK=1
	383	S7: OPPRESEND=1
	384	S8: MIN_FREQ=915000
	385	S9: MAX_FREQ=928000
	386	S10: NUM_CHANNELS=50
	387	S11: DUTY_CYCLE=100
	388	S12: LBT_RSSI=0
	389	S13: MANCHESTER=0
	390	S14: RTSCTS=0
	391	S15: MAX_WINDOW=131
	392
	393	The first column is the S register to set if you want to change that
	394	parameter. So for example, to set the transmit power to 10dBm, use
	395	'ATS4=10'.
	396
	397	Most parameters only take effect on the next reboot. So the usual
	398	pattern is to set the parameters you want, then use 'AT&W' to write the
	399	parameters to EEPROM, then reboot using 'ATZ'. The exception is the
	400	transmit power, which changes immediately (although it will revert to
	401	the old setting on reboot unless you use AT&W).
	402
	403	The meaning of the parameter is as follows:
	404
	405	- ``FORMAT`` - this is for EEPROM format version. Don't change it
	406	- ``SERIAL_SPEED`` - this is the serial speed in 'one byte form' (see
	407	below)
	408	- ``AIR_SPEED`` - this is the air data rate in 'one byte form'
	409	- ``NETID`` - this is the network ID. It must be the same for both your
	410	radios
	411	- ``TXPOWER`` - this is the transmit power in dBm. The maximum is 20dBm
	412	- ``ECC`` - this enables/disables the golay error correcting code
	413	- ``MAVLINK`` - this controls MAVLink framing and reporting. 0=no
	414	mavlink framing, 1=frame mavlink, 2=low latency mavlink
	415	- ``MIN_FREQ`` - minimum frequency in kHz
	416	- ``MAX_FREQ`` - maximum frequency in kHz
	417	- ``NUM_CHANNELS`` - number of frequency hopping channels
	418	- ``DUTY_CYCLE`` - the percentage of time to allow transmit
	419	- ``LBT_RSSI`` - Listen Before Talk threshold (see docs below)
	420	- ``MAX_WINDOW`` - max transmit window in msecs, 131 is the default, 33
	421	recommended for low latency (but lower bandwidth)
	422
	423	For two radios to communicate the following must be the same at both
	424	ends of the link:
	425
	426	- the radio firmware version
	427	- the AIR_SPEED
	428	- the MIN_FREQ
	429	- the MAX_FREQ
	430	- the NUM_CHANNELS
	431	- the NETID
	432	- the ECC setting
	433	- the LBT_RSSI setting
	434	- the MAX_WINDOW setting
	435
	436	the other settings may be different at either end of the link, although
	437	you will usually set them up the same at both ends.
	438
	439	Available frequency ranges
	440	==========================
	441
	442	The following table may be helpful matching your local radio regulations
	443	to the two radio models available
	444
	445	.. raw:: html
	446
	447	<table>
	448	<tbody>
	449	<tr>
	450	<th>Radio</th>
	451	<th>Minimum Frequency (MHz)</th>
	452	<th>Maximum Frequency (MHz)</th>
	453	</tr>
	454	<tr>
	455	<td>433</td>
	456	<td>414.0</td>
	457	<td>454.0</td>
	458	</tr>
	459	<tr>
	460	<td>900</td>
	461	<td>895.0</td>
	462	<td>935.0</td>
	463	</tr>
	464	</tbody>
	465	</table>
	466
	467	DUTY_CYCLE setting
	468	===================
	469
	470	Most users will want to set the ``DUTY_CYCLE`` to 100. The
	471	``DUTY_CYCLE`` is the maximum percentage of time that the radio will
	472	transmit packets.
	473
	474	The reason the duty cycle is included is that some regions of the world
	475	allow for higher transmit power or more frequencies if you have a duty
	476	cycle below a given threshold. So for example in Europe you can transmit
	477	on a wider range of frequencies in the 433 band if your duty cycle is
	478	below 10%.
	479
	480	When you set a duty cycle below 100% then your available bandwidth will
	481	be reduced, so you will find it will only work well for telemetry at
	482	higher baud rates. It is still quite practical to get good telemetry
	483	from an APM with a 10% duty cycle, as telemetry traffic is quite
	484	'bursty', so the average transmit time is not generally high anyway.
	485
	486	For example, you can easily receive all telemetry streams at 2Hz with
	487	``AIR_SPEED`` set to 128, ECC enabled and a ``DUTY_CYCLE`` set to 10.
	488
	489	You can also set a radio to receive only by setting the ``DUTY_CYCLE``
	490	to 0. That will work best if you set ``NUM_CHANNELS`` to a low number,
	491	as otherwise the clock synchronisation will be poor.
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			492
			493	.. _common-3dr-radio-advanced-configuration-and-technical-information_low_latency_mode:
			494
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			495	Low latency mode
			496	================
			497
			498	The radio can be configured to use 'low latency mode' to improve
			499	performance for things like tablet based joysticks etc... The two
			500	parameters you should set to enable this mode are as follows:
			501
			502	- Set ``MAVLINK`` to 2. This turns on special checking for the
			503	``RC_OVERRIDE`` packets used in joystick control, to allow those
			504	packets to always be sent first. If you are using mavlink (you
			505	probably are) there are no downsides for choosing this setting.
			506	- Change ``MAX_WINDOW`` from the default of 131 to 33. This will ensure
			507	that the GCS can send a packet to the vehicle at least once every 33
			508	msecs. It is worth noting that this will lower the available
			509	bandwidth, so if you need absolute maximum bandwidth you are best off
			510	with the default of 131. **Both radios on a channel must have the
			511	same value for this parameter, or they will not be able to talk to
			512	each other.**
			513
			514	Listen Before Talk (LBT)
			515	========================
			516
			517	The radio can implement 'listen before talk' (LBT) functionality to
			518	allow it to comply with a wider range of regional regulatory
			519	requirements. LBT is a system where the radio is required to listen for
			520	a period of time and see no signal from other radios before it is
			521	allowed to transmit. By using a non-zero ``LBT_RSSI`` value your radio
			522	will become more 'polite', by waiting until everyone else has stopped
			523	transmitting before starting to transmit itself.
			524
			525	To enable LBT in your radio you need to set the ``LBT_RSSI`` threshold.
			526	This is the signal strength that the radio considers to be an indication
			527	that the channel is busy. If you set ``LBT_RSSI`` to zero then LBT is
			528	disabled.
			529
			530	The minimum non-zero setting is 25 which is a few dB above the receive
			531	sensitivity of the radio (-121 dBm). To setup ``LBT_RSSI`` you need to
			532	know what signal level your local radio regulations require for LBT
			533	functionality. Each increment in LBT_RSSI above 25 is roughly equal to
			534	0.5dB above the radios receive sensitivity. So if you set LBT_RSSI to
			535	40 then the radio will consider the channel to be free if the signal
			536	strength is less than 7.5dB above the receiver sensitivity.
			537
			538	Alternatively, you can use this formula to get the received signal
			539	strength in dBm:
			540
			541	::
			542
			543	signal_dBm = (RSSI / 1.9) - 127
			544
			545	This formula is approximate, but quite close. See the Si1000 data sheet
			546	for a more precise graph.
			547
			548	You will need to lookup your local regulatory requirements to see what
			549	``LBT_RSSI`` setting you should use.
			550
			551	The LBT implementation in the radio uses a minimum listen time of 5ms,
			552	plus randomised listen time as per the European 9.2.2.2 rules.
			553
			554	Note that in many regions you need to implement LBT in conjunction with
			555	AFA (Adaptive Frequency Agility). The radio implements AFA as long as
			556	you have ``NUM_CHANNELS`` set to more than 1.
			557
	558	Upgrading radio firmware
	559	========================
	560
	561	The firmware for the radios is `open source <https://github.com/ArduPilot/SiK>`__, and new features are
	562	regularly added. You should check for new releases regularly to get the
	563	most from your radios.
	564
	565	The easiest way to upgrade is to:
	566
	567	- Connect the radio to be upgraded to your computer using the micro USB
	568	cable
	569	- Open the Mission Planner and go to the **Initial Setup \\| Optional
	570	Hardware \\| SiK Radio** page.
	571	- Select the correct COM port and set the baud rate to 57600. Ensure
	572	the "Connect" button is in a disconnected state as shown in the image
	573	below..
	574	- Press the Upload Firmware (Local) button and after a short delay,
	575	the "programming" message should appear and the green bar should
	576	slowly increase from the left to right.
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			577
			578	.. image:: ../../../images/Telemetry_3DR_Radio_UploadFirmware.png
			579	:target: ../_images/Telemetry_3DR_Radio_UploadFirmware.png
			580
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			581	The above process should be performed for both radios.
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			582
			583	.. note::
			584
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			585	Occasionally a new firmware update will modify some settings so it
			586	might be a good idea to compare the settings before and after and look
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			587	for changes.
			588
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			589	Using a FTDI-to-USB cable to configure SiK radios
			590	=================================================
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			591
			592	The recommended approach for configuring 3D Radios is to use Mission Planner,
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			593	:ref:`as discussed here <common-configuring-a-telemetry-radio-using-mission-planner>`.
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Mar 22, 2016 add all common documents			594
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			595	If that approach doesn't work do the following:
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Mar 22, 2016 add all common documents			596
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			597	#. Connect everything and configure the ground radio:
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			599	- Connect your air radio with FTDI-to-USB cable to your computer USB
			600	port & note Com port #
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			602	- Use Windows \\| Device Manager\\| Ports to identify com port #
			603	- You'll know the FTDI cable is correctly oriented on the air
			604	radio when a green LED blinks.
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			606	- Connect the ground radio to a USB port on your PC & note COM port #
			607	In MP Flight Data tab, at top right, set baud to 57600 &
			608	select ground radio COM port #
			609	- In MP Flight, press Ctrl + A to open the radio configuration
			610	window. Click on Load Settings (from the ground radio)
			611	- In Mission Planner radio configuration window, (MP) check the
			612	Advanced Options box
			613	- If loaded values aren't the same as above recommended settings,
			614	make it so, then click on Save
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Mar 22, 2016 add all common documents			615
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			616	#. Configure air radio:
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			618	- In MP at top right, select the air radio's COM port
			619	- In MP radio configuration window, click on Load Settings (from
			620	air radio)
			621	- Edit the air radio's settings (including Advanced Options) so they
			622	are exactly the same as the ground radio's, then click on
			623	Save Settings (to air radio)
			624	- You may not be able to add a value in the Format field, that's OK
			625	- In MP, press Configure \\| SiK Radio and enter exact same
			626	settings including advanced > click Save Settings.
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			628	#. Wait for both radios to connect (solid green LED)
			629	#. Update firmware if above doesn't work:
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			631	- Click on Update Firmware while connected to each radio in
			632	turn. Then repeat the above.
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			634	#. To verify wireless telemetry:
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			636	- Remove the FTDI to USB cable from APM
			637	- Connect the air radio to APM & LIPO
			638	- In MP \\| Flight Data tab select the ground radio COM port then
			639	click on Connect
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			640
			641	.. note::
			642
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			643	Keep in mind that while you are physically connected to a radio
			644	via a specific COM port, you can't use the 'Copy Required items to
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			645	Remote' button (there is no remote until you go wireless)
			646
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			647	*This section of the wiki was contributed by the Documentation User
			648	Group (DUG)*.
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Mar 22, 2016 add all common documents			649
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			650	Forcing bootloader mode
			651	=======================
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			653	If you somehow manage to get your radio in a state where you can't
			654	upload a new firmware via the Mission Planner then you may need to force
			655	the radio into bootloader mode.
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			657	The way firmware upload normally works is the planner connects to the
			658	radio and sends a AT&UPDATE command to put the radio into bootloader
			659	mode ready to receive a new firmware. That only works if the planner can
			660	send AT commands to the radio.
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			662	If you can't send AT commands, then you can force bootloader mode by
			663	shorting the CTS and GROUND pins on the radio while powering on. The red
			664	LED will light up when in bootloader mode.
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			666	On the air radios the CTS and GROUND pins are easy to find, as they are
			667	marked on the back of the radio (they are two of the FTDI connector
			668	pins). On the USB radios it isn't as obvious, so this diagram may help:
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			669
			670	.. image:: ../../../images/force-bootloader.jpg
			671	:target: ../_images/force-bootloader.jpg
			672
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			673	After you have the radio in bootloader mode you should be able to upload
			674	a firmware.
			675
			676	Technical Details
			677	=================
			678
			679	When evaluating if this radio meets your local regulations it may be
			680	helpful to know what technology it uses.
			681
			682	The firmware implements frequency hopping spread spectrum (FHSS) with
			683	synchronous adaptive time division multiplexing (TDM).
			684
			685	Specifically, the radio divides up the frequency range between
			686	MIN_FREQ+delta and MAX_FREQ-delta into ``NUM_CHANNELS`` channels. The
			687	'delta' value is a guard range to ensure that we stay well away from the
			688	edges of the allowed band. The guard range is set to half a channel
			689	width. The channel width is defined as:
			690
			691	::
			692
			693	channel_width = (MAX_FREQ - MIN_FREQ) / (NUM_CHANNELS+2)
			694
			695	Additionally, the radio skews the base frequency by up to one channel
			696	using a random seed based on ``NETID``. This means that two radios using
			697	different ``NETID`` numbers use slightly different frequencies.
			698
			699	The radios use GFSK (Gaussian Frequency Shift Keying) for transmission
			700	on a particular frequency.
			701
			702	The TDM works by dividing up time into slices, based on multiples of 16
			703	microsecond ticks. The time slicing is designed to give a maximum dwell
			704	time on any frequency of 0.4s (this is to meet US regulations). The TDM
			705	algorithm then works as follows:
			706
			707	- the EEPROM parameters determine a set of TDM parameters, particularly
			708	the transmit window and silence period, both are in 16 microsecond
			709	units. You can view the results using ATI6.
			710	- the transmit window is scaled to allow for 3 full sized packets to be
			711	transmitted
			712	- the silence period is equal to twice the packet latency, for the
			713	given data rate
			714	- The two radios synchronise their clocks automatically by adding 13
			715	bits of timestamp information to all packets. The timestamp is in 16
			716	microsecond units.
			717	- Each radio only transmits when it is 'their turn'. So a radio gets
			718	one transmit window worth of time, then there is a silence period
			719	when neither radio transmits, then the other radio gets its turn. We
			720	never have the situation where both radios transmit at the same time
			721	- the transmit channels are organised into a random sequence based on
			722	the ``NETID``
			723	- the frequency is changed to the next channel twice for each full TDM
			724	round, during the silence periods
			725	- when not transmitting, data that comes in over the serial port is
			726	buffered in a 2048 byte buffer
			727	- to prevent the buffer from getting too much data (which increases
			728	latency and risks overflow) the radios send information on how full
			729	the buffer is to the connected device. The APM code adapts its
			730	telemetry rates by small amounts to keep the amount of buffered data
			731	reasonable.
			732	- The TDM algorithm is also adaptive, in the sense that when it is the
			733	turn of radio A to transmit, it can send a small token to radio B
			734	saying "I don't need to send anything right now, you can take the
			735	rest of my timeslice". That is how the link auto-balances for
	736	asymmetric loads
	737	- during the initial search for another radio, and any time the link is
	738	lost, the radios go into a mode where they move the receiving
	739	frequency very slowly but move the transmit frequency at the normal
	740	rate. This allows the two radios to find each other for initial clock
	741	sync. How long this takes depends on the number of channels, the air
	742	data rate and the packet loss rate.
	743
	744	In some regions you may need to know the distribution of radiated energy
	745	within each channel. That depends on a number of factors, but mostly the
	746	frequency deviation used for the GFSK modulation. The following formula
	747	will give you an estimate of the frequency deviation:
	748
	749	::
	750
	751	frequency_deviation = air_data_rate * 1.2 min freq deviation = 40 max freq deviation = 159
	752
	753	where frequency_deviation is in kHz and the air_data_rate is in kilo
	754	bits per second.