Maybe everyone else knows this, but I just discovered that you can connect to the M5stickC over the serial connection and get a python prompt!

>plink -serial \\.\COM4 -sercfg 115200,8,1,n,n
[0;32mI (8) boot: ESP-IDF v3.3-beta1-696-gc4c54ce07 2nd stage bootloader
[0;32mI (9) boot: compile time 19:37:28
...
Connected. Network config: ...
Traceback (most recent call last):
  File "main.py", line 130, in <module>
  File "main.py", line 128, in <module>
  File "main.py", line 96, in GetAQI
NameError: name 'wait_ms' isn't defined
MicroPython v1.11-321-gac7da0a70-dirty on 2020-02-25; ESP32 module with ESP32
Type "help()" for more information.

I want to access the pre-existing WiFi config from micropython, the one you setup with M5burner.

On 1.4.5, on the M5StickC, the SSID + password are stored in apps/config.json. This is cool, as I don't have to hard-code it into my apps.

On 1.5.1, on the Core/Gray, there does not appear to be any equivalent file, yet it still knows the information. How do I access it?

I tried wifi_history = machine.nvs_getstr("history") from WifiCfg.py, but machine doesn't have nvs_getstr().

Is there any way to get this now? I really don't want to go back to hard-coding!

It there a more recent version of the micropython source than https://github.com/m5stack/M5Stack_MicroPython, which appears to be fairly old? (last updated on Aug 11, 2019). Or is that what's being used currently?

I found https://github.com/m5stack/micropython, which is more recent (Oct 31, 2021), but it doesn't seem to be as complete: For example, the tft code doesn't seem to be there.

For the A035 (https://docs.m5stack.com/en/unit/neopixel), what voltages should I use if I''m not using the grove connector, both for power and signal? I've seen some indication that maybe 5v for power is needed; would connecting a 3.3 signal work in that case? Don't want to let out the magic smoke!

From https://cdn-shop.adafruit.com/product-files/1138/SK6812+LED+datasheet+.pdf, it looks like--with a 5V supply--Vih is 3.4V, and 3.3V isn't going to hit that. But all those are "typical".

I'm trying to get file, function and line number to display in a message. I found a technique here (https://forum.micropython.org/viewtopic.php?t=7811), and tried to adapt it. It seemed to be working for a bit, but then somehow it stopped. The idea was to force an exception, which should dump a stack trace, then rummage through that. But for some reason, it is only showing the current function:

Traceback (most recent call last):
  File "lib/logging.py", line 46, in log
ValueError: foo
'Traceback (most recent call last):\n  File "lib/logging.py", line 46, in log\nValueError: foo\n'
line= Traceback (most recent call last):
line=   File "lib/logging.py", line 46, in log
INFO:Traceback (most recent call last)::ShowError (2000-1-1 0:0:14): error='WiFi connected'

Here's my code (borrowed in part from https://github.com/m5stack/M5Stack_MicroPython/blob/master/MicroPython_BUILD/components/micropython/esp32/modules/logging.py). Note that I also tried the seek(0) readline() thing from the example I'm copying, but it doesn't matter. In fact, just throwing a straight sys.print_exception(err) and letting it print out still doesn't show the stack.

    def log(self, level, msg, *args):
        if level >= (self.level or _level):
            redirect = io.StringIO()
            try:
              raise ValueError('foo')
            except ValueError as err:
              sys.print_exception(err, redirect)
            print('%r' % redirect.getvalue())
            caller = 'unknown'
            for new_line in redirect.getvalue().splitlines():
              print('line=',new_line)
              if 'logging.py' in new_line:
                break
              caller = new_line
            if caller != 'unknown':
              caller = caller_re.sub('[\\1:\\2](\\3)', caller)
            _stream.write("%s:%s:" % (self._level_str(level), caller))
            if not args:
                print(msg, file=_stream)
            else:
                print(msg % args, file=_stream)

I know from other code that I have that sys.print_exception(err) normally prints the stack, so I'm a bit flummoxed!

Any ideas where the stack trace went?

It there a more recent version of the micropython source than https://github.com/m5stack/M5Stack_MicroPython, which appears to be fairly old? (last updated on Aug 11, 2019). Or is that what's being used currently?

I found https://github.com/m5stack/micropython, which is more recent (Oct 31, 2021), but it doesn't seem to be as complete: For example, the tft code doesn't seem to be there.

On the m5stickc, uiflow's brightness is converted to axp.setLcdBrightness(level). This appears to be between 0 and 100, although 20 is barely visible in the dark.

The core gray doesn't have axp, but one can use lcd.setBrightness(level): This appears to be 0-255 from the doc, but realistically, it doesn't seem to matter above 25 or so. Is this documented anywhere?

@robalstona pin 0 is the clock, not ws, according to the sticker on the back. Don't know if that helps.

Thinking about how to test it: the M5StickC has no speaker.
OK, I have the Core Gray: It has a speaker! But no mic.
Maybe I could hook both of them together...
This is getting way too complicated for the idea I had in mind, which was some responsive blinky lights for Halloween. (Yes, it's next week. Your point?) :) I think I'll use the accelerometer instead.

Thanks! Going off that, I found this post, which points to the M5GO blob, which has

from machine import I2S

Going into REPL:

 from machine import I2S
>>> dir(I2S)
['__class__', '__name__', 'read', 'start', 'stop', 'write', '__bases__', '__dict__', 'CHANNEL_ALL_LEFT', 'CHANNEL_ALL_RIGHT', 'CHANNEL_ONLY_LEFT', 'CHANNEL_ONLY_RIGHT', 'CHANNEL_RIGHT_LEFT', 'DAC_BOTH_EN', 'DAC_DISABLE', 'DAC_LEFT_EN', 'DAC_RIGHT_EN', 'FORMAT_I2S', 'FORMAT_I2S_LSB', 'FORMAT_I2S_MSB', 'FORMAT_PCM', 'FORMAT_PCM_LONG', 'FORMAT_PCM_SHORT', 'I2S_NUM_0', 'I2S_NUM_1', 'MODE_ADC_BUILT_IN', 'MODE_DAC_BUILT_IN', 'MODE_MASTER', 'MODE_PDM', 'MODE_RX', 'MODE_SLAVE', 'MODE_TX', 'adc_enable', 'bits', 'deinit', 'init', 'nchannels', 'sample_rate', 'set_adc_pin', 'set_dac_mode', 'set_pin', 'volume']
>>> import wave
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: no module named 'wave'

So at least part of it is there! I found a listing of the class, but no documentation.

Then I found some examples, but they say Micropython after June 2021, so may not apply??

That talks about a "WS" pin, which I found described here.

The schematic shows only 2 pins however: SCL & SDA. The Unit unit :) appears to have WS tied to ground. Mouser indicates that the pin is tied low internally, and that is the left channel, but the arduino code sets it to I2S_CHANNEL_FMT_ALL_RIGHT.
Here's an I2S tutorial.
So, time to play I guess!

The posts are very confusing! Half say that it is i2s, and the Arduino code seems to support that. But the other half say that it is just an adc on port 34, and the micropython examples seem to support that!
I'm interested in using micropython.

Rshell works pretty well, although the newer M5 releases are a lot harder to get into the correct mode, particularly on the atom.

Uiflow is micropython: I have often written something in uiflow and then switched to the micropython side to see what the python is for a given uiflow thing. And then I can cut and paste into repl.

For long-term debugging (fails once a day or week), I leave the device connected to putty.

I have considered adding code that would catch Exception () in the main loop, do a stack trace, and save it into a file so that I don't need it to always be connected, but have never implemented it.

@medy mostly:

print(dir(wifiCfg))
print(wifiCfg.__dict__())

I'm sure that someone has written a function that formats all this, recurses, etc, but I usually just do it manually, because there are usually only a few things that make sense to try.

Also googling for micropython wifiCfg (or whatever), because micropython is not just for M5, and a lot of the code is on the internet. It's not always exactly the same, but it often is, or is close enough to provide hints for more things to look at.

I'm assuming that you know how to use rshell or some other tool to get to repl so that you can just type in statements as they occur to you, rather than writing a script for every new thing you want to try.