Accelerometer readings get "stuck" - please help

[Paulo]

Hi guys,
I'm working for a couple of days on an accelerometer data logger, and haven't been able to avoid the following problem:
- if I try to continuously retrieve Accel readings, even at very low rates (as 20Hz), after a short amount of time the readings get stuck; the Accel stops working and I have to reset the pyboard.
Can anyone help me with this?

Below is a simple block of code which already gives the problem.
Thanks!!

accel = pyb.Accel()
for i in range(1000):
print( accel.x(), accel.y(), accel.z() )
pyb.delay(50)

[pythoncoder]

I can't reproduce this, even increasing the loop to 10,000 passes. Have you anything connected to the GPIO lines of the Pyboard? If so, please give details. How is the Pyboard powered?

[shaoziyang]

It maybe cause by USB port or USB wire.

[Paulo]

Thanks pythoncoder and shaoziyang for your quick reply.
I'm using a PYBLITEv1.0-AC board. The pyboard is powered through the USB cable (and from your replies I sense this is an important point...)
In my application I'm also communicating with a GPS via UART [ pyb.UART(1, 9600) ]. I will check again if I get the accelerometer "stuck" at fixed values without the UART open.
While not actively using it in the code, I configure one pin for input [ pyb.Pin('X1', pyb.Pin.IN) ]. That's all about GPIO.
I run the example code I've sent (enough to generate the problem after a couple of seconds) via Putty.
Thanks!

[Paulo]

even without using any GPIO, I consistently get the Accel() readings "stuck" (example below) after some iterations in the loop

Code: Select all

a = pyb.Accel()
for i in range(1000):
    print( a.x(), a.y(), a.z() )
    pyb.delay(20)

the board is powered via USB, and this is the only code I'm running.
Any help/comments are appreciated. Thanks!

output example:
...
2 -1 -19
2 0 -20
3 -1 -20
4 -1 -19
-24 -20 -16
-24 -20 -16
-24 -20 -16
... (from now, stuck at this value)

[pythoncoder]

I've now located a Pyboard Lite and I still can't replicate this behaviour even with 10,000 iterations of your initial code. Perhaps you have a defective board?

[linuxcircle]

I have very similar problem. Accelerator readings got stuck only when I send data through serial port. As soon as I disable serial, it starts to read fine. Is there an interrupt or threading bug between serial and accelerometer?

[pythoncoder]

OK, I've now managed to replicate this on the Pyboard Lite AC and also a Pyboard V1.0. It's surely a bug. I will raise an issue. The following script locks the accelerometer every time:

Code: Select all

accel = pyb.Accel()
uart = pyb.UART(1, 9600)
print(accel.x(), accel.y(), accel.z())
uart.write( 'hello')
for _ in range(10): # It's locked. Waggle the board around and see nothing change
    pyb.delay(500)
    print(accel.x(), accel.y(), accel.z())

[linuxcircle]

Thanks for reporting it. Is there a way around this? I was thinking using a multi thread to separate the UART sending process with the accel reading process. Or perhaps getting a master - slave protocol where the slave on the board will only read accel value when asked.

Will upgrading the micropython firmware to latest version fix it?

Otherwise I would need an external module to read, which is adding to the bulkiness of the board.

They should really consider adding bluetooth module as default feature in next release.

[pythoncoder]

@Damien has pointed out that the accelerometer uses the same pins (I2C1: X9 and X10) as UART1. The above script works with a different UART. https://github.com/micropython/micropyt ... -258925948