host: Add native GPIO support for NXP based CPUs

[mCloud]

https://github.com/google/periph/blob/c091e84f02df7dc07db531cdf32af39bb1b37482/experimental/devices/mfrc522/mfrc522.go#L114

[maruel]

This should work on a Raspberry Pi and Allwinner A64 and R8 processors. What hardware and OS are you using?

[mCloud]

Thanks for your prompt reply. I use IMX6UL, linux kernel V4.1.15

[maruel]

ok I don't have a board with this cpu at hand so I can't help immediately with the support but I will welcome contribution towards supporting the family of NXP CPUs.

[maruel]

Update: I may get boards. Will update accordingly.

[maruel]

I received Pico i.MX7D boards, so I can start with this and then follow up on the IMX6UL as both are using a fairly similar design.

CPUs:

• NXP i.MX7D product page
  • NXP i.MX7D reference manual: Chapter 8: Chip IO and Pinmux; page 1599 and following.
• NXP i.MX6UL product page
  • NXP i.MX6UL reference manual Chapter 26 GPIO; page 1149

They both support 22K, 47K and 100K user selectable pull up and 100K pull down. That's really cool.

Boards:

• https://developer.android.com/things/hardware/imx7d
• NXP Pico Board page

[maruel]

I still have the board but given Android Things was shut down and nobody else requested support for it in the past 5 years, I'll close the request.

Please file a new issue at https://github.com/periph/host/ if you want NXP CPUs native support. Thanks.