RY835AI GPS Connections #142
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I thought I was the only one having strange GPS results. It seems to work for a while after I connect the GPS to my laptop and perform a cold reboot. Then re-connect it to Stratux via GPIO. I am open to help with testing and coding. |
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Some discussion a while back regarding long lock times centered around the small capacity of the onboard lithium cell. It's something like 50mAh, which is maybe around a week of standby tops. Most (not all) of us are probably flying less than weekly, so it has plenty of time to drain and then think it's off the coast of Equatorial Guinea. I don't know that anyone else has fiddled with the wiring, but at the time I wondered about replacing the tiny cell with a bigger one like a lithium CR3032, which is 500mAh. |
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starting a new thread on realistic hardware goals |
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The issue I have with GPS is not related to it being off too long. I can have a WAAS lock on it, power cycle the Stratux. Then end up with either no GPS lock after letting it sit powered on over night. Repeated power off's won't fix it. I have to perform a GPS cold restart to have it re-establish a lock. I have used the ubox windows tool to monitor what is going happening and noticed that it will be quick to pickup a couple of satellites. Not enough to even get to 3D tracking. And they will all drop for a second and it has to find them again. |
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The NEO-M8M data sheet states for both GPS/GLONASS and GPS/BeiDou configs You'd need to use u-center to get the 5Hz UBX-CFG-RATE-Measurement period // Set 10Hz update. from the NEO-M8 data sheet TCX) or Crystal GNSS GPS & GLONASS GPS &BeiDou GPSMax nav update rate NEO-M8N 5Hz 5Hz 10Hz On Mon, Dec 14, 2015 at 7:01 AM, brockhoff notifications@github.com wrote:
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factory default I believe is 1hz and I doubt anyone is changing that config.. could be wrong. looking at the data sheet and seeing 3 ground signals and most are only wiring one ground to me sounds like it could be an issue.. signal grounds are key to keep noise out of the signal waveforms going to the pi.. garbage in garbage out? |
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On Mon, Dec 14, 2015 at 9:17 AM, duecedriver notifications@github.com
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nope didnt catch that.. honestly having a hard time finding and following documentation on the project.. central documentation would really help people figure out whats going on without having to read all the source code for notes or at least a running doc for each process... keep in mind that even with a good backup battery ... saved almanac and ephemeris data is only good for a short period of time... ephemeris data is considered good for 30 mins.. otherwise its a cold start what is probably happening on cold starts is the gps start position might be defaulting back to a lat long of 0 ,0 in that case with an inaccurate start location and no almanac it takes the unit forever to orient to the constellation and get its initial fix and begin the 13 minute almanac download.. then update ephemeris with a hand held or other consumer gps.. if it senses its a cold start.. it usually asks you to click on a present position on a map to give it a head start. in the USAF, we were required to take our survival radio/handhelds out periodically from our survival gear and let it update almanac data and get a starting fix.. and they had huge batteries.. for the U-2, it was usually connected to a external gps antenna and let it align and warm up for over an hour during preflight to have a highly precise location and ephemeris updates.. but then my INU was so sensitive it had to calibrate for more than an hour to sense the earths rotation too |
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if allowing the user to specify a default starting point for the GPS will significantly accelerate lock, then that would not be a big thing to add. Doe the hardware support setting the lat/lon starting position? What do others think? |
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Have you checked the cgsic site for possible gps sat outage? On 12/14/2015 07:01 AM, brockhoff wrote:
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This kind of stuff isn't what I do, but I'm just trying to help so apologies if this is redundant or useless. That said... Looking over the M8 Documentation Section 9, it lists the ways to speed up starts but most require the host to fetch data from the Internet. Their "AssistNow Autonomous" (Section 9.6) seems the most useful to us as it works completely offline with data it already has:
It sounds like it adds a few days of life to the last ephemeris. Not great, but better than nothing. It's also disabled by default. Does this sound like something worth turning on? |
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My guess is it is not a problem with the GPS taking long on a cold startup. If I force it to do a cold startup then it will get a 3D lock in about 15-20 mins. After it gets a 3D lock I will power it off/on. So I would expect the battery would be able to hold the satellite almanac and allow it to get 3D lock quickly. this does happen most of the time. But some times it does not. And when It does not then it will never get a 3D lock until I force a cold startup. I was also thinking about all the ground connections on the RY835AI. I an email to their support and they never answered my question. This issue does not appear to happen when I connect the RY835AI to the Stratux USB. |
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Yes, AssistNow will help - if anyone wants to add in it would be great. @jamez70 ?? |
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If you think that would help we could make it work. uBlox doesn't give access to that freely though if I remember correctly. I had mentioned previously that at my day job we had to switch uBlox 8 modules because one of them would either take a very long time to lock or not lock at all. |
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Just forwarded you my API key for the u-blox AssistNow data files |
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Cool thanks. I'll look at it tonight On Mon, Dec 14, 2015 at 7:27 PM, cyoung notifications@github.com wrote:
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Ok, I wrote something and it might work. I did a pull request so you could take a look. If you could, test it. I need to check acknowledgements though before I would call it done. |
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Ok I wrote some code, but need to test it more On Mon, Dec 14, 2015 at 7:28 PM, Jim Jacobsen jamez1970@gmail.com wrote:
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We have been using the same pin configuration since August, I have seen a picture on reddit recently that had the ground jumped to another pin. Since the beginning we have been using the pin configuration that @duecedriver has posted with a single ground on pin 6. This configuration has seemed to work for a lot of folks. Not sure where the extra ground is coming from, maybe I missed something? IMO I think that some folks are just getting bum GPS units or their soldering skills are not up to the task, also that unit is pretty small, there is a chance that in the process of soldering the headers you could actually damage or overheat it. |
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Well the more I look at the schematic the more inclined I am to thinking we have not taken the time to wire this chip correctly. From what I remember of digital and analog ic curcuit design..(25 years ago), multiple grounds to ensure voltage floors and waveform squareness are not put on the boards for their good looks. additionally, there is pin 8 which is an input pin FSYNC for the MPU, it states wire to ground if not used. there is a blurb in the u-block data sheet that warns that all grounds and voltages be carefully managed to avoid over stressing components as they can be damaged by voltage spikes and voltage float. Again we are hooking into the pi +5 line that is notoriously unreliable especially when 2 radios are being used without the powered hub, we give it a single ground (which may only gound the 5v power source) not providing a ground for the 3.3v signal generator sources that may further allow voltage float and not provide square waveforms as well as not allowing any onboard filters a current drain. So convinced that this is (part) the problem I found a blurb in the u-blox hardware integration manual that states Electromagnetic interference on I/O lines https://www.u-blox.com/sites/default/files/NEO-M8_HardwareIntegrationManual_(UBX-13003557).pdf we are also clearly not utilizing all data i/o pinouts and I cant speak to their individual requirements but this may also explain why folks have less issues over usb. The USB spec requires the i/o and power to be internally regulated (and all relevant circuits would be tied and grounded appropriately in the onboard usb circuit) .. when utilizing the header pins, we are now responsible for ensuring all power and grounds are good, that all data channels are connected to their various sources and targets, etc.. I am fairly convinced that we need to have someone that is a lot smarter than me reference the hardware integration guides of these chips to figure out how to wire it for full performance. also the u-bloc guides talk a lot about assisted startup additionally power wise the pi has no good data/time to feed the unit so after a couple days the unit power on and the onboard clock starts at its hard coded date, it has no location, and it requires the full cold start... thoughts |
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why dont we put the GPS on the i2c bus with the ahrs? again. I am trying to get with reyax to see how they are using the 6050.. are they outputing raw axis data or using the 6050 onboard software processing that is supposed to fuse the data. a 6050 on a separate breakout board gives you the option.. I dont know what there are doing here. We are also not using the fsync or interrupts while most of the other people using a 6050 are using these.. lacking the additional grounds that the chip provides may be allowing noise into the ahrs data? |
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It is difficult to use interrupts in standard Linux, which is what's on On 12/17/2015 08:39 AM, duecedriver wrote:
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If you want to get DMP (Digital Motion Processor) output from the 6050, play with this: https://github.com/cyoung/linux-mpu9150 It's not using hardware interrupts, there is a sample queue on the 6050 which is small - and depending on the sample rate, usually can be read in without missing or overflowing. Not the best setup but you can at least use it to evaluate the performance roughly. |
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We don't use FSYNC because this isn't a mobile phone, and we're not trying syncrhonize accelerometer signals with optically stabilized image capture. Tying the grounds together is a red herring. All of the grounds on the RY835AI board are tied, with < 0.2 Ohm resistance, because the whole bottom layer of the board, save for the signal and power traces, is one big ground plane. Even the gold-plated mount pads on the corners of the board are part of the ground. In my experience, an electrically "clean" M8N receiver will position lock within three minutes on a cold startup -- that's indoors, with no real-time clock, no almanac, no previous position. That said, EM interference can be and is a problem. I've seen UART noise show up as gibberish on the serial console (i.e. |
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what I want to know is if its even available in the RY chip.. they have the 6050 on board but it has 2 modes.. which are they using.. the manufactured cant even tell me.. invensence.. the company that makes it finally opened up the code to use it for developers.. you can get a free account to access the standards and some example code routines.. but did reyax make it available or not?
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What modes are you referring to? |
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Things get really complex with the "DMP". The DMP ("Digital Motion Processor") can do fast calculations directy on the chip. This reduces the load for the microcontroller (like the Arduino). The DMP is even able to do calculations with the sensor values of another chip, for example a magnetometer connected to the second (sub)-I2C-bus. |
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the DMP package is supposed to do all the vector calcs etc.. it is on an i2c bus with the compass and pressure sensor according to the reyax .pdf but they cant tell me if the installed it to use the DMP or not.. invensence has a developer section I think I sent you a link where you can now download the code and the developers tools and specs for the 6050 but if it was not installed by reyas to get at it.. it may or may not work... |
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there is probably a world of difference on how the bus and signal noises are on the ground in the kitchen vs in the aircraft sitting on top of the avionics stack with a 60 yo generator providing enough noise to power detroit ...and a transponder and other radios leaking RF |
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@AvSquirrel ok fair enough on fsync.. however according to the manufacturers integration doc.. if it is not used it is supposed to be grounded. additionally, if a singe ground would work I dont see why they provide 3.. again... I have read the integrators docs for the 6050 and the GPS chip on this board and they all harp on the ground criticality as well as RF shielding and ESD damage potential ... |
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correct, the fsync is for the 6050 and its i2c internal... but its still a ground and signal source so it should be wired correctly to prevent noise from entering the components.. any components on the board |
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Dumb question, can you use USB just for GPS and GPIO for the AHRS ? I seen posts where users are reporting less than 12 satellites when using only the pins. |
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You can |
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yep however I cant find on the spec sheet what the max update rates are over one vs there other.. and dont forget to harden the micro usb connector with some epoxy or something or it will break off in short order. grounding of the board and shielding the board and giving the antenna a ground plane will improve even the usb connected device
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I've seen numerous comments about usb working better for people than pins. Why would this be? It can't be grounding because the microusb header looks to connect to the same ground plane as everything else. It can't be the floating FSYNC pin, because it's it's floating when on usb (unless it's disabled via software?). |
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the usb standard would require the power and grounding and signal shielding etc.. the gps is still going out over the serial bus into the header pins witch require those wires to have good solder joints and the noise on the ground plane would be a bigger issue since the signal paths move about that ground plane... or it could be a hardware issue on the reyax side if they didnt integrate the chip properly.... |
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Can someone point me in the right direction. I am new to this. I have assembled the receiver with the GPS. I have made the connections in the post. I can see the GNSS LED flashing, but I am not getting GPS output. Am I missing something? Any help would be appreciated. If this is not the correct form, my apologies |
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Have you enabled the GPS in the Web UI? |
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Thanks for replying. Yes, everything is enabled. I am getting AHRS, traffic, and weather. The AHRS symbol is skewed, but I see that is still being worked on. Sent from my iPad
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A couple of other things to try; Very the wiring between the RY and the R-Pi. The most common error is swapping the TX and RX lines. Also, if the GNSS led is blinking and you still doing see any GPS data on the Web UI, try cycling power on the Pi. Sometimes it sherbet sync up with the GPS data if the GPS starts let. This was addressed in 0.5r4 or 0.5r5 but it doesn't hurt to reset. On February 3, 2016 3:05:19 AM CST, tdarrow notifications@github.com wrote:
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Does it work with the USB cable? That should tell you if it's your wiring or not. |
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Are there any advantages to direct wiring vs. using the RY835AI via USB? From: braddward [mailto:notifications@github.com] Does it work with the USB cable? That should tell you if it's your wiring or not. — |
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I don't know if the AHRS works with USB. Also, I've heard that the USB On Wed, Feb 3, 2016 at 8:44 AM Josef Zeevi notifications@github.com wrote:
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It frees up a USB port for a different use. Remember too, the USB connection can only connect the GPS portion, not the AHRS portion of the RY835AI. |
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Got it. For me, as a Foreflight user, that’s currently not a problem. I’ll look at direct wiring, though – seems like that offers more opportunity. J Thanks! From: JohnOCFII [mailto:notifications@github.com] Are there any advantages to direct wiring vs. using the RY835AI via USB? It frees up a USB port for a different use. Remember too, the USB connection can only connect the GPS portion, not the AHRS portion of the RY835AI. — |
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I tried both way, and did not receive any data. I'm not sure if I have a bad chip. I tried to check it with the ublox center, but I could not get it to see the sub ports. Sent from my iPad
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were you able to disconnect the hard-wired connections? If you did and it On Wed, Feb 3, 2016 at 10:09 AM tdarrow notifications@github.com wrote:
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On the RY, you should get a solid light at power up (I think it's green), and then once it receives a GPS lock it blinks (i think red) once a second. I may have the colors reversed, but there's a green one and a red one; a solid one and a blinking one. You can't get a blinking one without a solid one. You only mentioned a blinking light. Are you seeing both? |
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One last thing - you may want to leave it on for an extended period in a On Wed, Feb 3, 2016 at 10:40 AM Nokomis449 notifications@github.com wrote:
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I checked the connections. I had to switch the transmit and receive around. As soon as I did that I has GPS signal. I then shut the pi down so that I could reassemble the case. Now I have the green power led, but no red flashing led. When I look at the status on the web page I see the following UAT towers 0 I am currently letting it sit next to a window to see if there is any change Sent from my iPad
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I have never gotten a signal from my RY835AI. Lights are on and blinking but not GPS, no AHRS. I have radio ADS-B hits but no positions. |
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Send it to me and I'll test it for ya. On 02/05/2016 01:42 PM, scmadden wrote:
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You could try cat /dev/ttyACM0 (is that it?) With gen_gdl90 stopped
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Or minicom or cutecom, or etc. I'm thinking it is more of a hardware On 02/05/2016 04:24 PM, jamez70 wrote:
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When I connect it to my computer I get a gps signal. Just not coming through the stratux. |
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@scmadden USB or GPIO? If GPIO, try USB and see if you get anything. |
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I have tried both. GPS connection just this afternoon broke. Shawn C. Madden, Ph.D.
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Try Reddit or Slack if further support needed. |
Looking for definitive pinouts and settings based on the latest .5 beta code. These are the latest pinouts most are using but the RY835AI shows multiple trigger grounds... should we be using or tying the grounds to ensure proper operation? There are many people posting of intermittent signal, long lock times, and other abnormalities.. are we hooking this up right!
Also, does the stratux code set the units internal settings for gps refresh rates>? The unit comes factory default at 1HZ but can be modified up to 18Hz. How about baud rates and ports? Some hook up via usb then connect to gpoi and that solves some issues.. so I am thinking this is a gps board settings issue.
Does the hardware store almanac and ephemeris data for warm/hot and assisted startup or do we need to store that via software. I assume some settings (port data/refresh rates/etc) are being retained in the unit via non vol memory while catalog and gps ephemeris are being held by the rechargeable onboard battery. Anyone test how long that battery lasts?
as for the gyros and other sensors.. see my other post.. I believe there are sever good open source code projects that will give us full AHRS and imu/inu functionality.
Power:
VDD -> PIN 02
GND -> PIN 06
AHARS Data:
SDA1 -> PIN 03
SCL1 -> PIN 05
GPS Data:
TXD -> PIN 10
RXD -> PIN 08
spec sheet here
http://www.reyax.com/Module/GPS/RY835AI/RY835AI.pdf
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