Arduino Library for KT0803 and KT0803K FM transmitter.
In different countries there are different laws with respect to using transmitting devices and their range. Please inform yourself of the local rules and laws if and how you may or may not use a device like the KT0803 in your projects, either hobby, commercial or otherwise.
This experimental library allows basic control of the KT0803 and / or the KT0803K FM transmitter device. It is primary written to understand the possibilities and the interface of the device.
The library is not tested by me with hardware yet. See future below.
There are newer, more capable, follow up devices like model K, L and M. From these only the KT0803K is supported as a derived class. The L and the M versions of the device will work with the KT0803K class too as their functionality is equal or exceeds the K version. As far as investigated the L and M versions are backwards compatible.
Version 0.3.0 implements a few KT0803K specific functions, see section below. These will work for L and M devices too.
For ATTinyX5 series there exists the TinyKT0803 class which is derived from this one. It uses a different I2C implementation. See - https://github.com/RobTillaart/TinyKT0803
Read datasheet for details.
Warning The KT0803 is an 3.3 Volt device and cannot be connected directly to 5V MCU's.
+----------+
| KT0803 |
GND --| 1 16 |-- PA_OUT RF analog output
Crystal XI --| 2 15 |-- GND
Crystal XO --| 3 14 |-- SCL I2C Clock
3.3V IOVDD --| 4 13 |-- SCA I2C Data
GND --| 5 12 |-- GND
in left INL --| 6 11 |-- GND
in right INR --| 7 10 |-- RSTB Reset
enable SW --| 8 9 |-- GND
| |
+----------+
The frequency range stated on the front page of the datasheet ==> 70 MHz - 108 MHz. The frequency range stated in table 2 ==> 76 MHz - 108 MHz. So the datasheet is at least ambiguous on this point.
Keep in mind that the frequency range allowed differs per country. The library does not provide this filtering, explicit responsibility of the user.
The KT0803K device has far more options, which are not all implemented. There is one important, the resolution or step-size of the frequency.
| device | step-size | Notes |
|---|---|---|
| KT0803 | 100 KHz | in code all math is done with 50 KHz |
| KT0803K | 50 KHz |
Backwards compatible. According to the datasheet code for the KT0803 should work for the KT0803K. Code with the KT0803K class will probably not work on a KT0803.
The transmit frequency can be set with setFrequency(MHz) or by setChannel(channel). Note that the channel and frequency math of the KT0803 and the KT0803K is aligned in this library. This allows exchange of channel data between device types.
Note that the KT0803 will internally round to use 100 KHz steps.
Some examples:
| Frequency | Channel | Notes |
|---|---|---|
| 70.00 MHz | 1400 | channel = freq (Mhz) * 20 |
| 70.05 MHz | 1401 | freq = channel * 0.05 |
| 70.10 MHz | 1402 | |
| 76.00 MHz | 1520 | |
| 80.00 MHz | 1600 | |
| 89.70 MHz | 1794 | default (see registers datasheet) |
| 100.00 MHz | 2000 | |
| 101.30 MHz | 2026 | |
| 105.70 MHz | 2114 | |
| 108.00 MHz | 2160 |
- https://github.com/RobTillaart/KT0803
- https://github.com/RobTillaart/TinyKT0803
- https://www.hackster.io/hesam-moshiri/stereo-digital-fm-transmitter-circuit-arduino-code-2dbd8d
- https://www.hackster.io/hesam-moshiri/full-digital-fm-receiver-with-arduino-and-tea5767-52be37
- https://www.hackerstore.nl/Artikel/388
- https://en.wikipedia.org/wiki/FM_broadcasting
#include "KT0803.h"- KT0803(TwoWire *wire = &Wire) constructor, optional Wire interface.
- KT0803K(TwoWire *wire = &Wire) constructor, optional Wire interface.
- bool begin(float freq = 90.0, bool mute = true) initializes the library. Furthermore it checks if the deviceAddress is available on the I2C bus. Default it sets the frequency to 90 MHz and mutes the signal. Returns true if deviceAddress is found on the bus, false otherwise.
- bool isConnected() test to see if deviceAddress is found on the I2C-bus.
- bool setFrequency(float MHz) converts the frequency in MHz to call setChannel(channel). The value of channel is rounded off depending on the resolution of the device. Returns false if MHz is out of range or setChannel() fails.
- float getFrequency() returns the current frequency in MHz, can be slightly different from the set value due to rounding math mentioned above. The return value is derived from a call to getChannel()
- bool setChannel(uint16_t channel) writes the channel to broadcast on to the device. This involves two or three writes to different device registers.
- uint16_t getChannel() reads the selected channel from the device and returns it.
Read Datasheet.
The KT0803K has a PGA_LSB (2 bits) setting, which allows setting the gain with single (1) dB steps. This is not yet implemented in the library.
- bool setPGA(uint8_t pga) sets gain according to table below. Returns false if pga is out of range (0..7).
- uint8_t getPGA() returns 0..7, default 0.
| PGA | gain | notes |
|---|---|---|
| 111 | 12dB | |
| 110 | 8dB | |
| 101 | 4dB | |
| 100 | 0dB | |
| 000 | 0dB | default |
| 001 | -4dB | |
| 010 | -8dB | |
| 011 | -12dB |
Read Datasheet.
Note: the RFGain value (4 bits) is distributed over three registers. PA_BIAS (register 0x05) is only supported in the KT0803K device. It is not yet supported in the library.
- bool setRFGain(uint8_t rfgain) sets rfgain according to table below. Returns false if rfgain is out of range (0..15).
- uint8_t getRFgain() returns 0..15, default 15.
| RFGAIN | RFout | PA_BIAS = 1 | notes |
|---|---|---|---|
| 0000 | 95.5 dBuV | - | |
| 0001 | 96.5 dBuV | - | |
| 0010 | 97.5 dBuV | - | |
| 0011 | 98.2 dBuV | - | |
| 0100 | 98.9 dBuV | - | |
| 0101 | 100.0 dBuV | - | |
| 0110 | 101.5 dBuV | - | |
| 0111 | 102.8 dBuV | - | |
| 1000 | 105.1 dBuV | 107.2 dBuV | |
| 1001 | 105.6 dBuV | 108.0 dBuV | |
| 1010 | 106.2 dBuV | 108.7 dBuV | |
| 1011 | 106.5 dBuV | 109.5 dBuV | |
| 1100 | 107.0 dBuV | 110.3 dBuV | |
| 1101 | 107.4 dBuV | 111.0 dBuV | |
| 1110 | 107.7 dBuV | 111.7 dBuV | |
| 1111 | 108.0 dBuV | 112.5 dBuV | default |
Read datasheet for details.
Note that not all frequencies are allowed in all regions / countries!
The first four are convenience wrappers for setPHTCNST() If some region is missing please let me know the details and I can add a wrapper for it.
- void setEurope()
- void setAustralia()
- void setUSA()
- void setJapan()
- bool setPHTCNST(bool on) See table below.
- bool getPHTCNST() returns set value.
| PHTCNST | time | Region |
|---|---|---|
| 0 | 75 μs | USA, Japan, (default) |
| 1 | 50 μs | Europe, Australia |
Read datasheet.
- bool setPilotToneAdjust(uint8_t mode) HIGH = 1 LOW = 0
- uint8_t getPilotToneAdjust()
Default the device is not muted, but begin() will default mute it. See interface section above.
- bool setMute(bool mute) enables or disables the transmitting by muting the signal.
- bool getMute() returns the current state of muting.
The device and library do not implement the persistant store of user selectable preferences (frequencies or channels). This can be implemented by the user in EEPROM or another persistent medium.
Think of a class that holds an array of channels and optional descriptions. A minimal hardcoded preset sketch is in the examples.
A derived class KT0803K class is created, with some extended functions.
The KT0803L will work as it is backwards compatible with KT0803K. It has far more registers in use than the KT0803/K.
The KT0803M is identical to the KT0803K (no new registers), so a derived class is straightforward.
Added functions in 0.3.0 (not tested), check datasheet.
- bool setMono() idem
- bool setStereo() idem
- bool isStereo() idem
- **bool setBass(uint8_t bass); // 0..3 = 0, 5, 11, 17 dB
- uint8_t getBass() idem
- bool powerOK() idem
- bool silenceDetected() idem
- improve documentation
- buy hardware
- test and verify.
- update readme.md
- KT0803K specific functions.
- add examples for KT0803K specific functions.
- RESET pin as optional parameter in constructor?
- SW pin (ON/OFF) as optional parameter in constructor?
- add functions for sw on/off,
- what is impact on settings?
- call begin () again? => default
- explain well doc.
- derived class KT0803M == KT0803K
- derived class KT0803L >= KT0803K (compatible)
- improve error handling
- unit tests possible?
- extend settings upon request bold are interesting, see table
| device | setting | register | Notes |
|---|---|---|---|
| KT0803 | PA_CTRL | 13, bit 2 | WARNING in datasheet |
| Should it be added in API? | |||
| KT0803K | PGA_LSB | 04, bit 4+5 | gain fine tuning -> see PGA_MOD |
| KT0803K | FDEV | 04, bit 2+3 | Frequency deviation adjustment |
| KT0803K | PDPA | 0B, bit 5 | Power Amplifier Power Down ? |
| KT0803K | PA_BIAS | 0E, bit 1 | PA bias current enhancement. |
| KT0803K | LMTLVL | 10, bit 3+4 | Internal audio limiter level control |
| KT0803K | PGAMOD | 10, bit 0 | PGA mode selection (use PGA_LSB/ not) |
| KT0803K | SLNCDIS | 12, bit 7 | Silence detection disable |
| KT0803K | SLNCTHL | 12, bit 4+5+6 | Silence detection low threshold |
| KT0803K | SLNCTHH | 12, bit 1+2+3 | Silence detection high threshold |
| KT0803K | SW_MOD | 12, bit 0 | Switching channel mode selection |
| KT0803K | SLNCTIME | 14, bit 5+6+7 | silence detection time |
| KT0803K | SLNCCNTHIGH | 14, bit 2+3+4 | silence detection count high |
| KT0803K | SLNCCNTLOW | 15, bit 0+1+2 | silence detection count low |
- investigate tea5767 FM receiver (Out of scope for this lib).
- investigate efficiency of register access.
- caching all (allowed) registers in begin()
- 3 bytes for KT0803
- 12 bytes for KT0803K
- cache frequency.
- only writing is needed.
- caching all (allowed) registers in begin()
- send binary data over FM?
- preset frequency array in .h file (hardcoded)
- enums for parameters - readability?
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