What about UART serial port 5?

[ahebert]

Questions:
Are there 5 or 6 serial ports available?
If 6, what are the pins for UART #5?
If 5, what is the expected behavior of the constructor call `UART(5)`

Elaboration:
Looking at the doc for pyb.uart: https://micropython.org/doc/module/pyb/UART, it says

Construct a UART object on the given bus. bus can be 1-6...

Then in the following paragraph:

The physical pins of the UART busses are:

UART(4) is on XA: (TX, RX) = (X1, X2) = (PA0, PA1)
UART(1) is on XB: (TX, RX) = (X9, X10) = (PB6, PB7)
UART(6) is on YA: (TX, RX) = (Y1, Y2) = (PC6, PC7)
UART(3) is on YB: (TX, RX) = (Y9, Y10) = (PB10, PB11)
UART(2) is on: (TX, RX) = (X3, X4) = (PA2, PA3)

UART(5) is not given. Does it exist?

Thanks!

[dhylands]

There is a UART5, but it's mapped onto CPU pins PC12 & PD2

On the pyboard, PC12 goes to the sdcard connector to be used for SDIO_CK, and PD2 goes to the sdcard connector to be used for the SDIO CMD signal.

So, in order to use UART5, you would lose the ability to use the sdcard.

[ahebert]

Ah, that makes sense. Thanks for your reply!

Does it require any special code or firmware besides `uart(5)` to use those serial port pins (and override the pins as used the SD card)? For example, would I need to use the `pyb.Pin` class?

(BTW, I'm asking for a project that uses 6 serial ports, and it'd be great to do it all with one board.)

[dhylands]

It looks like you'd need to add an entry for UART5 to this file:
https://github.com/micropython/micropyt ... #L186-L208

and here:
https://github.com/micropython/micropyt ... #L563-L572

Some other boards, like the STM32F407 Discovery or perhaps the http://www.wvshare.com/product/Core405R.htm may give easier access to all of the UART pins than the pyboard does.

[ahebert]

Wow, thanks dhylands!

That's exactly what I was looking for in terms of what to change (in the firmware, in this case). And that ST evaluation board may be just the perfect thing (though I'm quite enamored with the pyboard at the moment.

Thanks again for your excellent help.