drivers/nRF24L01: Updated for ESP8266 with machine/SPI syntax

[mcauser]

Works between two of my WeMos D1 Minis, each running MicroPython v1.8.6-204-gde9cd00

WeMos D1 Mini	nRF24L01+
D4 GPIO2	CE
D5 GPIO14	SCK
D6 GPIO12	MISO
D7 GPIO13	MOSI
D8 GPIO15	CSN
GND	GND
3V3	VCC
N/C	IRQ

Copy /drivers/nrf24l01/esp8266/*.py into /esp8266/modules/
cd esp8266
make clean && make axtls && make deploy

On slave device:

>>> import nrf24l01test
>>> nrf24l01test.slave()

On master device:

>>> import nrf24l01test
>>> nrf24l01test.master()

[deshipu]

See #2285 too.

[mcauser]

And #2354. I should really check unmerged PRs first.

[mcauser]

Closed in favour of almost identical changes #2285

[peterhinch]

The current test/example program nrf24l01test.py uses the pyb module and hence is not portable. Would it not be worthwhile to replace it with this portable one?

[dpgeorge]

Would it not be worthwhile to replace it with this portable one?

Yes that's a good idea, but the one here is not 100% portable because it relies on specific pins of the ESP8266.

In 54acd0b I made the test script use utime and machine modules to make it more portable. Feel free to submit a PR to make it run on both pyboard and esp8266.

[peterhinch]

Please see #3366 for discussion of a portable solution.