isREPLconnected & isUSBconnected

[ladyada]

could be handy to be able to query, from the python side, if USB is enumerated and/or the REPL is opened!

put down for 3.0 but can be long-term

[sommersoft]

I've been researching this between Travis battles. I think I've got USB mostly figured out, but still working on a plan for REPL. Initially I was hoping it could go into the micropython module. But, with USB being handled at the port level, somewhere in shared-bindings & common-hal is probably better. I imagine REPL will end up the same way, given the REPL flavors on different ports.

Here are my USB notes so far.

• Atmel-SAMD: ports/atmel-samd/usb.c is an easy place to grab usb_connected(), which points to the CDC handlers.

• ESP8266: ports/esp8266/machine_uart.c seems to me the only place to grab USB state by polling UART0. I don't understand ESP's USB fully yet, so this is just going off of my reading. I dug around ESP's SDK a little and didn't see anything else that jumped out at me.

• nRF: seems similar to ESP8266 in needing to poll UART0. ports/nrf/hal/hal_uart.c has hal_uart_available().

For where to put the function calls, board seems the syntactic choice to me, but I understand not wanting to break from the "here lie the pins" approach. microcontroller would be my next guess. I defer to you all on that one.

I'm ok with being assigned on this one, but definitely not trying to block anyone out from doing it. I just wanted to document that I'm looking at it, and start the conversation on the particulars.

Lastly, please let me know if I'm way off in my approach. I'm well known for trying to make things more difficult than they actually are.

[tannewt]

@sommersoft seems like you are headed the right direction! I think a new supervisor module and singleton would be best.

[sommersoft]

So, after a few more days crawling around the core, I think checking for a live REPL connection isn't currently possible. One exception to that is WebREPL; that would be doable by checking for the file stats. Of course I caveat all of this with "I am very possibly wrong", but here is how I've come to that conclusion.

1. Starting at circuitpython/main.c:L#119, the boot code checks serial_connected(), and if it is, it prints out the startup info to the REPL. (there is at least one other place where the serial is checked before sending/listening to REPL...but it's all rapidly congealing inside my brain and I forgot where I saw it)

2. serial_connected() is in circuitptyhon/ports/????/supervisor/serial.c for each port.

   • atmel-samd: serial_connected returns the result of usb_connected() (see above comment)
   • nrf: serial_connected() returns True...always. As in, it's hardcoded: return true; (L#66)
   • esp8266: actually uses it's own main.c which has a slightly different method, but it works the same by just checking for a serial connection. There is also the added use of WebREPL.

In summary, there is no active REPL state information; it all just assumes if the serial connection, through USB/BLE/Web, is active then we should send and listen for REPL activity.

I'll keep digging into it, but I think I've hit bedrock...

I've got USB check running on SAMD. I'll start working the others soon.

[tannewt]

Use serial_connected to determine whether serial is connected. Rename isREPLconnected to isSerialConnected in your brain. Many folks confuse REPL with serial.

I think USB enumeration status would be a bit more difficult actually. I don't believe we track it at this point.

[sommersoft]

So, I'll press forward with just extending serial_connected to the python layer. I want to dig a little on the nRF port being hardcoded to return true;, though.

I started to look at checking/tracking USB enumeration...a bit out of my depth. That ASF4 stuff is seriously fragmented. Don't know how you and Dan deal with that on the regular...

[tannewt]

The nRF may not be able to tell because it uses a separate USB to UART chip. The newer ones will do USB but this probably hasn't been updated for it.

Do a PR for the serial connection first and then do usb enumeration separately.