Problem getting HMC5883L to work

All ESP8266 boards running MicroPython.
Official boards are the Adafruit Huzzah and Feather boards.
Target audience: MicroPython users with an ESP8266 board.
laukejas
Posts: 20
Joined: Thu May 02, 2019 5:17 pm

Re: Problem getting HMC5883L to work

Post by laukejas » Sat Mar 21, 2020 6:07 pm

Hey, Roberth, sorry to bother you again, but I still get some problems running that code for QMC5883 that you wrote. The device worked fine for a few days, and now suddenly it freezes on function read_raw. For example, if I run it via the normal way, calling

Code: Select all

x, y, z, temp = qmc5883.read_scaled()
then the console freezes, and if I abort with ctrl+c, it prints:

Code: Select all

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "QMC5883.py", line 156, in read_scaled
  File "QMC5883.py", line 144, in read_raw
KeyboardInterrupt: 
I haven't touched the hardware since when this setup worked. Neither changed anything in the code. i2c.scan() still recognizes the device properly. Do you have any ideas what could be causing this?

EDIT: I assume the hanging happens when the read_raw() calls ready(). So when I called print(qmc5883.ready()), and it prints 0. I'm not exactly sure what that means.

EDIT 2: I added 4.7K resistors to SDA and SCL pins, and one one boot I got the ENODEV error again. Unpluged USB, plugged it back again, opened serial, ran the code - no ENODEV this time, but the code hangs again on the read_raw() function. It all feels so very random, but I can't point my finger at it. Even when I make absolutely no changes to hardware, and repeat exact same steps, I sometimes get random results - sometimes it works, sometimes it hangs, sometimes it's the ENODEV error... How do I debug such a thing?

User avatar
Roberthh
Posts: 1889
Joined: Sat May 09, 2015 4:13 pm
Location: Rhineland, Europe

Re: Problem getting HMC5883L to work

Post by Roberthh » Sat Mar 21, 2020 7:51 pm

qmc5883.ready() returning 0 means, that not data is available for reading. Are you sure that you did not change anything?
What is the result of calling:

qmc5883.i2c.readfrom_mem(QMC5883.ADDR, QMC5883.X_LSB, 6)

or

qmc5883.i2c.readfrom_mem(QMC5883.ADDR, QMC5883.X_LSB, 14)

laukejas
Posts: 20
Joined: Thu May 02, 2019 5:17 pm

Re: Problem getting HMC5883L to work

Post by laukejas » Sat Mar 21, 2020 8:00 pm

Calling qmc5883.i2c.readfrom_mem(QMC5883.ADDR, QMC5883.X_LSB, 6) returns:

Code: Select all

b'\x00\x00\x00\x00\x00\x00'
And calling qmc5883.i2c.readfrom_mem(QMC5883.ADDR, QMC5883.X_LSB, 14) returns:

Code: Select all

b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
Please also see my edits in the previous reply... Something really weird is going on here.

User avatar
Roberthh
Posts: 1889
Joined: Sat May 09, 2015 4:13 pm
Location: Rhineland, Europe

Re: Problem getting HMC5883L to work

Post by Roberthh » Sat Mar 21, 2020 9:11 pm

Replace the wires to your breakout board. If that does not help, the chip may be broken.

laukejas
Posts: 20
Joined: Thu May 02, 2019 5:17 pm

Re: Problem getting HMC5883L to work

Post by laukejas » Sat Mar 21, 2020 9:23 pm

Replaced them... I had cheap Chinese jumpers there, now I replaced with proper quality wires. But I'm still getting random things happening. I did three attempts to read. First attempt: ENODEV error. Second read: command hung up and had to be aborted. Third attempt: reading was successful, but x, y and z are all zero.

If the chip was broken, shouldn't the errors be consistent? And how can it be broken when it worked fine just a few days ago? I power it from 3.3V rail from my NodeMCU. Never had any higher voltage anywhere near it. Perhaps it needs some decoupling capacitors or something? I mean, I now have three qmc5883 chips, one of them says ETIMEDOUT all the time, second one says ENODEV all the time, and third one is totally random. This can't be a coincidence...

Post Reply