IoTGateway/BSP/Android/Gettingstarted/How to use UART

Overview

The Android/Linux UART/serial port access from user is through the tty-devices. The tty-devices have different names depending on UART driver on different board.

Configuration

standard baud rate

The utility stty can configure the serial speed. Then the com port can be accessed as a file:

Check baudrate

# stty -F /dev/ttymxc1 115200

Read

#cat /dev/ttymxc1 &

Send

#echo test > /dev/ttymxc1 

Change COM mode

The COM port need to change mode for user space (APK). your can add the chmod cammand in the android init.rc file in device/fsl/rom_3420_a1/.

ex: chmod 666 /dev/ttymxc*

RS-485

RS-485 uses half-duplex communication, which means that one medium is shared for transmitting and receiving data. Therefore the system needs to control the RS-485 transceiver's transmit mode. Usually the UART RTS signal is used to switch the transmitter on and off. Our modules provide the following support:

Enable the RS-485 feature by either using ioctrl TIOCSRS485 from user space as described in RS-485 Kernel Documentation.

 

Boards

ROM3420 Borad

COM Name	NXP/Freescale Name	Device	RS485 support
COM0	UART2	/dev/ttymxc1	Yes
COM1	UART4	/dev/ttymxc3	Yes
COM2	UART5	/dev/ttymxc4	Yes

 

ROM7421 Borad

COM Name	NXP/Freescale Name	Device	RS485 support
COM0	UART2	/dev/ttymxc1	No
COM1	UART4	/dev/ttymxc3	No

Test Sample

1. Click "Serial Port"

2. Click "Setup"

3. Click "Device" , and choose the used device(e.g. ttymxc1)

4. Click "Baud rate" , and choose the used baudrate(e.g. 115200)