Avoid a longint as a cmd arg

[dhalbert]

This fixes #27.

PR #26 introduced a longint as a cmd arg, which makes the library fail on non-longint builds, such as Feather M0 Adalogger. I reworked the _cmd() method to take either an integer or a bytes, so non-longint constants can be expressed in the code.

@michelkluger, would you like to test? I can supply a .mpy if you need one.

[michelkluger]

Yes, i can Test it tomorrow at work and feedback you about the result.

Thanks a lot for taking a look into that. My scientific project will benefit a bunch from a working library :)

[michelkluger]

send me the .mpy when you can =)

Thanks in advance for the effort

[atwalsh]

Can confirm this resolves the issue described in #27, tested on an Adalogger M0.

@michelkluger I built the .mpy using:

Adafruit_CircuitPython_SD/.travis.yml

Lines 30 to 31 in 5ad33e4

	- circuitpython-build-bundles --filename_prefix adafruit-circuitpython-sd --library_location
	.

[michelkluger]

Can you provide me the .mpy file? I am yet to learn how to cross compile and everything. I'm pretty new to the embedded world

Thanks

[dhalbert]

@michelkluger Sorry for the delay. Unzip this (I can't post a .mpy directly):

adafruit_sdcard.mpy.zip

[michelkluger]

this is working like a charm =)

Thanks a lot

[dhalbert]

@michelkluger Great, we'll publish this as a release. Thanks for your testing!

[michelkluger]

@dhalbert is there a way to extract the data from the sd card to the pc, using the usb connection, without having to physically remove the card and plug in the slot?

[dhalbert]

@michelkluger It is very difficult to expose the SD card filesystem as a mass storage device. I think the discussion here may be helpful to explain why: adafruit/circuitpython#2206.

[michelkluger]

but is it possible to stream the bytes somehow via usb (not as a mass storage device )? or ftp to grab the data?

it is not essential, but if there is a known method I would implement in my code

[dhalbert]

You can always just print the data. For boards that didn't have mass storage USB support, there are tools for doing file transfer over serial. Take a look at https://github.com/scientifichackers/ampy (we used to support this, but transferred it to someone else).

[atwalsh]

There's a post on the MicroPython forums discussing something that I have been wanting to try out. It looks like they are using the pyb library specific to the pyboard, but I wonder if something similar could be achieved with CircuitPython supported boards. This is unrelated to the PR, but I wanted to see if you know what they are discussing (exposing SD card through USB of the board) is possible on these boards.

[dhalbert]

This is getting off the PR, and feel free to open a new issue. That post describes using rshell (similar to ampy) to get the data, or to mount the SD filesystem instead of the internal filesystem. It's not possible to present both filesystems via USB MSC.