Adafruit mlx90640_camtest.py example does a "black screen" in RPi4

[Pedalbo]

The example from adafruit (mlx90640_camtest.py) crashes the RPi4 all the time! This means that when I run the example, the screen goes black and I need to shut down the RPi4. Don't even have time to get the error. The example mlx90640_simpletest.py and also mlx90640_pil.py works good though... any thoughts?

[ladyada]

you need to run it from a command line or something to get the error message

[Paul760]

I have the same problem. I got an adafruit MLX90640 today. Testing it now with my Raspberry Pi 4 with 4gb RAM gives an working mlx90640_simpletest.py. From the command line is nice and smooth. I can see my face :-)

But the mlx90640_camtest.py is not working. It gives a black screen. The error I see is:

pi@desktop1:~/Adafruit_CircuitPython_MLX90640/examples $ python3 mlx90640_camtest.py
pygame 1.9.4.post1
Hello from the pygame community. https://www.pygame.org/contribute.html
<VideoInfo(hw = 0, wm = 1,video_mem = 0
         blit_hw = 0, blit_hw_CC = 0, blit_hw_A = 0,
         blit_sw = 0, blit_sw_CC = 0, blit_sw_A = 0,
         bitsize  = 32, bytesize = 4,
         masks =  (16711680, 65280, 255, 0),
         shifts = (16, 8, 0, 0),
         losses =  (0, 0, 0, 8),
         current_w = 2560, current_h = 1440
>

MLX addr detected on I2C, Serial # ['0x1223', '0xb6ea', '0x189']
6
Refresh rate:  32 Hz
Traceback (most recent call last):
  File "mlx90640_camtest.py", line 124, in <module>
    mlx.getFrame(frame)
  File "/usr/local/lib/python3.7/dist-packages/adafruit_mlx90640.py", line 126, in getFrame
    status = self._GetFrameData(mlx90640Frame)
  File "/usr/local/lib/python3.7/dist-packages/adafruit_mlx90640.py", line 155, in _GetFrameData
    raise RuntimeError("Too many retries")
RuntimeError: Too many retries

[BLIII]

I have experienced the same issue that @Paul760 referenced above. My implementation is custom and actually does not output anything to a screen; it just reads temps. I am running my code on a Raspberry Pi 3 B+.

At first, I thought this may have been a frequency issue because I was trying to run the camera at 32Hz however it also happens at 16Hz and 8Hz as well.

I know that the runtime error is getting thrown from this section of code but I don't quite understand the reason behind keeping a count within the while loop and then raising a runtime error of "too many retries". I will say that if I remove the following two lines from the code, the implementation seems to work just fine. I just don't know the history behind it so I am not comfortable pushing a PR to remove it unless I am confident it is not needed. Does anyone know the reason for why it exists?

        if cnt > 4:
            raise RuntimeError("Too many retries")

[renegade2k]

Well, as i was just stuck at the same point and was searching for a workaround for lot of time now, there it goes:
simply change the refresh rate for the "working on image"-code of the example to a lower rate.
There for you must change the line:
mlx.refresh_rate = adafruit_mlx90640.RefreshRate.REFRESH_8_HZ # set refresh rate
to
mlx.refresh_rate = adafruit_mlx90640.RefreshRate.REFRESH_4_HZ # set refresh rate

This will make the code work at least for the beginning phase.
Also this will result in a 0.2 fps video, so don't expect too much.

[ladyada]

unclear why some pi+camera combos are fine at higher rate and some are not (we wrote the code on a pi 4 originally so it ought to still work?) .

if someone can update the example to put a hint about trying different refresh rates, and submit a PR, that would be great!

[BLIII]

Is this what you had in mind, @ladyada? I figured adding the comment to the main README would be a better spot than adding comments to each example in the examples directory. If you would like to see that though, let me know and I can re-submit.

#27

[ladyada]

sure, seems fine - other folks in this thread can check it out too

[Chimajero]

hi!, recently I have acquired two mlx modules,
At first, I also had errors between 8 and 64 hz on Raspberry Pi Zero 2 W.

On melexis github, there is a closed issue that talks about "of too many retries":

melexis/mlx90640-library#57

A commit was made in April 2020 to solve it.
There are changes in:

int MLX90640_GetFrameData(uint8_t slaveAddr, uint16_t *frameData);

and two new method:

int ValidateFrameData(uint16_t *frameData)

int ValidateAuxData(uint16_t *auxData)

I tried to do the same on my local library:

def _GetFrameData(self, frameData):
        dataReady = 0
        cnt = 0
        statusRegister = [0]
        controlRegister = [0]
        data =[0]*64
        while dataReady == 0:
            self._I2CReadWords(0x8000, statusRegister)
            dataReady = statusRegister[0] & 0x0008
            # print("ready status: 0x%x" % dataReady)
        self._I2CWriteWord(0x8000, 0x0030)
        self._I2CReadWords(0x0400, frameData, end=768)
        self._I2CReadWords(0x0700, data, end=64)
        self._I2CReadWords(0x800D, controlRegister)
        frameData[832] = controlRegister[0]
        frameData[833] = statusRegister[0] & 0x0001
        
        returned_data = self._ValidateAuxData(data)
       
        if returned_data == 0:
            for cnt in range(0,64):
                frameData[cnt+768]= data[cnt]
                
        returned_data = self._ValidateFrameData(frameData)
        if returned_data != 0:
            raise RuntimeError("_ValidateFrameData_error",-2)
        return frameData[833]

def _ValidateAuxData(self, auxData):
        if auxData[0] == 0x7FFF:
            return -8
        for i in range(8,19):
            if(auxData[i] == 0x7FFF):
                return -8
        for i in range(20,23):
            if(auxData[i] == 0x7FFF):
                return -8
        for i in range(24,33):
            if(auxData[i] == 0x7FFF):
                return -8
        for i in range(40,51):
            if(auxData[i] == 0x7FFF):
                return -8
        for i in range(52,55):
            if(auxData[i] == 0x7FFF):
                return -8
        for i in range(56,64):
            if(auxData[i] == 0x7FFF):
                return -8
        return 0;

    def _ValidateFrameData(self, frameData):
        line = 0
        for i in range(0,768,32):
            if (frameData[i] == 0x7FFF) and (line%2 == frameData[833]):
                return -8
            line = line + 1
        return 0

Now I can increase the frequency, but the frame rate is slow. That's why I have added in /boot/config.txt, this line

dtparam=i2c_arm_baudrate=1000000

(Beware, if there are other modules on the same i2c they may dont like the line on /boot/config.txt )

Now works in 8hz, 16hz, 34hz, 62hz, but sometimes there are other errors: I2c, math errors in sqrt, division by zero..( on high frequencies ). I added a block "try-except-continue" on my main to "hide those errors" and when they occur i read a new frame again. Maybe someone can do this better, I'm a python newbie.

(There are other new methods on melexis API)

[ladyada]

thanks, if someone is up for adding the new validation functions to a PR we can review and add them to the library!