esp8266: Support SPI bus with only MOSI or MISO line

[tdicola]

Right now the nativeio.SPI class seems to require both MOSI and MISO to be specified, for example on esp8266:

>>> import nativeio
>>> import board
>>> spi = nativeio.SPI(clock=board.SCK, MOSI=board.MOSI)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
OSError: Pins not valid for SPI
>>> 

Compared to specifying both MOSI and MISO which does work fine:

>>> spi = nativeio.SPI(clock=board.SCK, MOSI=board.MOSI, MISO=board.MISO)
>>>

Talking earlier we do think supporting just a MOSI or MISO makes sense and this might be a small bug.

[tannewt]

OK, my guess is that it only works on atmel-samd. I'll have to look at it for esp. Thanks!

…

On Mon, Dec 12, 2016 at 3:16 PM Tony DiCola ***@***.***> wrote: Right now the nativeio.SPI class seems to require both MOSI and MISO to be specified, for example on esp8266: >>> import nativeio >>> import board >>> spi = nativeio.SPI(clock=board.SCK, MOSI=board.MOSI) Traceback (most recent call last): File "<stdin>", line 1, in <module> OSError: Pins not valid for SPI >>> Compared to specifying both MOSI and MISO which does work fine: >>> spi = nativeio.SPI(clock=board.SCK, MOSI=board.MOSI, MISO=board.MISO) >>> Talking earlier we do think supporting just a MOSI or MISO makes sense and this might be a small bug. — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#65>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AADNqeOrOwUFYGSw7W9h8D_SR6FqMrLwks5rHdW-gaJpZM4LLJc2> .

[deshipu]

You can disable the miso/mosi pins in the ESP8266's SPI peripheral, but currently the flags that do that are hardcoded in the HSPI functions -- you would need to change that.

See for example https://github.com/adafruit/circuitpython/blob/master/esp8266/hspi.c#L248