How to use UARTs

Overview

This How-To is meant to be a starting point for people to learn use UART for IGEP v2 devices as quickly and easily as possible. In this how-to, we use a program (upload source code), executed twice, at the same time inside the same IGEP.  Its function is get a number via UART, increase it and send result to other UART, the result will be a infinite loop between 2 UARTs. This program was testedin Linaro Headless with Kernel 2.6.35.y.

More information about UART.

Note: This program have a debug option using GPIOs to debug via oscilloscope, this option is useful to learnt about the Kernel latencies and IRQ. Debug has set to "write" and "select" functions.

Feedback and Contributing

At any point, if you see a mistake you can contribute to this How-To.

Preparing IGEP

To test UARTs we use UART0 (dev/ttyS0) and UART3 (dev/ttyS2) via J960 connector.

By default, UART0 is used by RS485 driver, we need to disable RS485 support, go to igep.ini file and search line:

board.ei485= yes

Maybe you don't fond this line, replace by or type this:

board.ei485= no

By default, UART3 is used by Kernel serial console, we need to disable it, go to igep.ini file and comment next line:

console=ttyS2,115200n8

Testing UART

Under Construction