UART

The phyFLEX-AM62Px provides access to up to 8 UART interfaces that can be used for configuration and data exchange with external peripheral devices.

By default, the phyFLEX-Libra AM62Px is configured to use UART1 for a Linux console input and output. The UART1 signal is available through the USB-C connector X14 via a UART to USB bridge. PHYTEC recommends allocating UART1 for console access on custom designs. You can see the UART interfaces available on the phyFLEX-Libra AM62Px in the images and tables below.

phyFLEX-AM62Px UART Connectors

The UART channels correspond to the following connectors and system paths.

UART

UART

Connector

Character Device File

Status

UART1

X14 (USB-C, FT4232H USB to UART bridge)

/dev/ttyS2

Default Linux Console

UART0

X27 (RS-232/RS-485 2x5 Header)

/dev/ttyS3

Requirements

  • DB9 Male 2x5 to RS232 Female Cable (included in the development kit)

  • USB to RS-232 serial adapter

Hardware Setup

  • Power off and remove the power supply from the phyFLEX-Libra AM62Px.

    am62pxx-phyflex-libra-rdk-1:~# poweroff

  • Set DIP switch S5 to OFF to select RS-232 (ON selects RS-485).

  • Connect the DB9 Male 2x5 to RS232 Female Cable (included in the development kit) to the X27 connector (red line indicates Pin 1).

  • Connect a USB to RS-232 serial adapter to the female end of the DB9 cable. Do not connect the cable to your host system yet.

X27 Pin Mapping

Signal

Pin

RS-232 RXD

3

RS-232 RTS

4

RS-232 TXD

5

RS-232 CTS

6

RS-485 A

7

RS-485 B

8

GND

9, 10

  • Power the phyFLEX-Libra AM62Px back on.

  • Connect the USB to RS-232 serial adapter to your host system. Inspect the dmesg output on your host system to find its device file. The USB debug port X14 already provides /dev/ttyUSB0 to /dev/ttyUSB3, so the adapter will very likely be /dev/ttyUSB4. The host commands below use /dev/ttyUSB4.

Setting the Baud Rate

Before using the UART interface, you need to configure the baud rate. The following command sets the baud rate to 115200 bps for the UART interface:

am62pxx-phyflex-libra-rdk-1:~# stty -F /dev/ttyS3 115200

You can verify the current settings using:

am62pxx-phyflex-libra-rdk-1:~# stty -F /dev/ttyS3 -a

Sending Messages

To send data through the UART interface, you can use the echo command to write to the device:

am62pxx-phyflex-libra-rdk-1:~# echo "Hello World" > /dev/ttyS3

For continuous transmission, you can use a loop:

am62pxx-phyflex-libra-rdk-1:~# while true; do echo "Test Message" > /dev/ttyS3; sleep 1; done

Receiving Messages

To read incoming data from the UART interface, set the baud rate of the serial adapter and use the cat command:

sh-host:~$ stty -F /dev/ttyUSB4 115200 raw -echo
sh-host:~$ cat /dev/ttyUSB4

This will display any incoming messages in real-time. Press Ctrl+C to stop reading.

For debugging purposes, you can also use minicom. Install it using:

sh-host:~$ sudo apt update
sh-host:~$ sudo apt install minicom

Start minicom:

sh-host:~$ minicom -D /dev/ttyUSB4 -b 115200

Booting via UART

See chapter UART on how to boot from UART.