Using motorkit with Adafruit DC Motor Bonnet on Jetson Nano

[littlebee]

Hi! I'm trying to get the Adafruit DC & Stepper Motor Bonnet working on a Nvidia Jetson Nano 4Gb using MotorKit.

I followed the instructions for setting up Circuit Python on the Nano. The motor board is connected to the directly to the Nano and powered sepately from the Nano.

I2C shows the two I2C addresses:

$i2cdetect -y -r 1
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: 60 -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: 70 -- -- -- -- -- -- --

When I try to from adafruit_motorkit import MotorKit in python3 console, however, I get an error:

>>> from adafruit_motorkit import MotorKit
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/bee/.local/lib/python3.7/site-packages/adafruit_motorkit.py", line 42, in <module>
    import adafruit_motor.motor
  File "/home/bee/.local/lib/python3.7/site-packages/adafruit_motor/motor.py", line 26, in <module>
    from pwmio import PWMOut
  File "/home/bee/.local/lib/python3.7/site-packages/pwmio.py", line 48, in <module>
    raise NotImplementedError("pwmio not supported for this board.")
NotImplementedError: pwmio not supported for this board.

I additionally tried enabling the PWM pins using jetson-io.py, but that didn't fix the error. My jetson GPIO config looks like:

|                Select desired functions (for pins):                |
 |                                                                    |
 |                 [ ] aud_mclk      (7)                              |
 |                 [ ] i2s4               (12,35,38,40)                    |
 |                 [*] pwm0           (32)                             |
 |                 [*] pwm2           (33)                             |
 |                 [*] spi1              (19,21,23,24,26)                 |
 |                 [ ] spi2              (13,16,18,22,37)                 |
 |                 [ ] uartb-cts/rts (11,36)                          |
 |                                                                    |
 |                                Back                                |

Thank you for any help!

[tekktrik]

PWM support may be available on the Jetson Nano based on my brief look at Blinka, @makermelissa is that correct? If so, then it seems like because that library relies on pwmio you wouldn't be able to use it on that board. :/

[tekktrik]

Oh, but they're only used for type annotations, so I guess that's what's causing the issue in the Blinka environment.

[tekktrik]

Looping in @FoamyGuy. We could create a typing.Protocol to alleviate the issue, but would it be best in the Blinka library? Should we create it in the library itself even though this issue may arise other places? We could try for native Blinka support and fall back on a circuitpython_typing-based typing.Protocol that could be added.

[FoamyGuy]

I don't have any experience with pwm on Blinka and have never used a jetson nano, so I can't add much to that discussion.

I do think a protocol makes sense if that import is only used for typing though. My first instinct would be to put it into circuitpython_typing instead of Blinka directly. iirc the type helpers were moved from Blinka into the circuitpython_typing library so that they could be used by Blinka and in other places needed like this library.

[tekktrik]

Okay, I think adding a typing.Protocol there that could actually be imported for typing in a Blinka environment should resolve this. I can get on that.

[tekktrik]

Whoopsie! Didn't mean to close

[tekktrik]

Opened an issue for adding the protocol. Once that's merged (or the decision is made to move the protocol into adafruit_motor) I can write a fix for this!

[tekktrik]

HI @littlebee, if you upgrade adafruit_motor to 3.4.0 (now on PyPI), it should fix your problem!

[littlebee]

Thank you!!! That totally works. So glad not to have to switch boards!