Wrong pins on sh1106 spi example

[Garfius]

Been trying for 2h+, and finally discovered the SPI wiring pins on the comments are wrong.

Instructions goes as (wrong):
` Sample code sections
------------ SPI ------------------
Pin Map SPI

• 3v - xxxxxx - Vcc
• G - xxxxxx - Gnd
• D7 - GPIO 13 - Din / MOSI fixed *1
• D5 - GPIO 14 - Clk / Sck fixed *2
• D8 - GPIO 4 - CS (optional, if the only connected device)
• D2 - GPIO 5 - D/C
• D1 - GPIO 2 - Res
  `

But only works if you use (right):
`
Pin Map SPI

• GPIO 11 - Din / MOSI fixed *1
• GPIO 10 - Clk / Sck fixed *2
  `

Also may include a suggestion to use a logic level adapter, because there are 5v sh1106 displays.

Link to photo of working set, also using lg. lvl. adap. 5v

The mistake is located at:
https://github.com/raspberrypi/pico-micropython-examples/blob/master/i2c/1106oled/sh1106.py

Thanks 4 the great work.

[lurch]

ping @robert-hh (whose name appears in sh1106.py)

Took me a little while to figure out what was going on here, as https://github.com/raspberrypi/pico-micropython-examples/tree/master/i2c/1106oled only shows an I2C wiring-example. But then I figured out that this issue is referring to the code comments in sh1106.py rather than any actual example code? So then I managed to figure out that the SPI pins used are actually "allocated" by the line: # spi = SPI(1, baudrate=1000000). So then I found up https://github.com/micropython/micropython/blob/master/ports/rp2/machine_spi.c#L44 which confirms that for SPI interface 1, the default MOSI pin used by MicroPython is GPIO11 and the default SCK pin is GPIO10.

Which matches up with what @Garfius has written above 😁

I'll give it a couple of days to see if Robert responds, and if he doesn't I'll fix up the SPI-related pin-number code-comments in https://github.com/raspberrypi/pico-micropython-examples/blob/master/i2c/1106oled/sh1106.py myself 🙂

[robert-hh]

Thanks for the Ping. Actually, the driver is a pretty old one, initially made for a ESP8266 set-up. So the pin numbers in the example at the header of the driver code are for this device. In a repository for Rp2040 it should indeed match the pins of a rp2 board. Since I do not own that repo, I can only make a PR for a change, which I will do.

[lurch]

I can only make a PR for a change, which I will do.

Thanks! 👍

[robert-hh]

About the suggestion of note on 5V devices. That's not needed since:

• the logical section of the sh1106 chip itself runs at 3.3V, and so it matches the RP2040.
• and even if it were a 5V device: Only inputs of that module are driven by the RP2040. So there is no risk of a damage. Eventually the the high level of the RP2040 could be to low to be recognized by a 5V device. But I never had problems.

[robert-hh]

@lurch I made that PR. The example code in the sh1106.py header is tested and works for both SPI and I2C.