Enabling UART2

[rgreen]

Hardware: Pine H64 Model B
Hat: Elelabs Zigbee Raspberry Pi Shield


Step 1. Software

• Started from fresh, simple, Armbian (by way of DietPi) install.
  

• Disabled uart serial consoles with armbian-config/dietpi-config. (Or not, I re-enabled and used it later.)
  

• Add:
  
  Code:

  overlays=uart3
  to /boot/armbianEnv.txt
  
• Reboot
  
• confirm device creation with
  
  Code:

  dmesg | grep tty
• Output should be close to: [    3.819251] 5000c00.serial: ttyS3 at MMIO 0x5000c00 (irq = 26, base_baud = 1500000) is a 16550A
  
• If you aren't sure peripheral is working use uart0 as a loop back source by connecting uart0TX(EXT Pin 1) to uart3RX( Pin 36), and uart0RX(EXT3) to uart3Tx(pin 37).  You can then use "screen /dev/ttyS3 baudrate" to read input
  

Step 2. Hardware

• Identify adapter pins
               ________
               |  |  |  |3|2|
  Pin 1-->|1|  |  |  |4|
  

Adapter <---> UART3 Pins:
1 VCC <---> 3v3 - Pin 1
2 TXD <---> uart3 RX - Pin 36
3 RXD <---> uart3 TX - Pin 37
4 GND <---> GND - pin 39


Step 3. Reverse TX and RX that you hooked up backwards despite checking 3 times.

Step 4.... Profit!

Reference:
https://wiki.pine64.org/wiki/PINE_H64

Files:
https://files.pine64.org/doc/Pine%20H64/...ematic.pdf  - NOTE - pin assignments differ from my particular model B
https://files.pine64.org/doc/Pine%20H64/...rev2.0.pdf - NOTE - These assignments DO reflect my Model B but I don't even know where this file came from anymore.