DART-MX8M UART: Difference between revisions

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--> {{PageHeader|{{#var:HARDWARE_NAME}} UART}} {{DocImage|category1=DART-MX8M|category2=Yocto}} __toc__
--> {{PageHeader|{{#var:HARDWARE_NAME}} UART}} {{DocImage|category1=DART-MX8M|category2=Yocto}} __toc__


= DART-MX8M UART Overview =
= {{#var:HARDWARE_NAME}} UART Overview =
All 4 UARTs on DART-MX8M are enabled by default.<br>
All 4 UARTs on {{#var:HARDWARE_NAME}} are enabled by default.<br>
UART1 is connected to debug console, UART2 and UART3 are connected to J12 header on DART-MX8M carrier board, UART4 is connected to Bluetooth module.<br>
UART1 is connected to debug console, UART2 and UART3 are connected to J12 header on {{#var:HARDWARE_NAME}} carrier board, UART4 is connected to Bluetooth module.<br>
On DART-MX8M SoMs without WIFI/BT module UART4 is also connected to J12 header.<br>
On {{#var:HARDWARE_NAME}} SoMs without WIFI/BT module UART4 is also connected to J12 header.<br>
See the [https://www.variscite.com/wp-content/uploads/2018/04/VAR-DT8MCustomBoard-Datasheet.pdf carrier board datasheet] for the exact pinout.<br>  
See the [https://www.variscite.com/wp-content/uploads/2018/04/VAR-DT8MCustomBoard-Datasheet.pdf carrier board datasheet] for the exact pinout.<br>  
Only UART4 has RTS and CTS lines.
Only UART4 has RTS and CTS lines.
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</pre>


For each time you run this echo command the "hello" string should appear on the terminal.
For each invocation of echo command the "hello" string should appear on the terminal.


= Disabling UART2 =
= Disabling UART2 =

Revision as of 08:40, 28 February 2019

UART

UART Overview

All 4 UARTs on are enabled by default.
UART1 is connected to debug console, UART2 and UART3 are connected to J12 header on carrier board, UART4 is connected to Bluetooth module.
On SoMs without WIFI/BT module UART4 is also connected to J12 header.
See the carrier board datasheet for the exact pinout.
Only UART4 has RTS and CTS lines.

UART naming under Linux

The Linux devices corresponding to UART1 - UART4 are /dev/ttymxc0 - /dev/ttymxc3 respectively.

Testing UART2

Short J12.4 and J12.6 pins and run the following commands:

stty -F /dev/ttymxc1 -echo -onlcr 115200
cat /dev/ttymxc1 &
echo hello > /dev/ttymxc1

For each time you run this echo command the "hello" string should appear on the terminal.

Testing UART3

Short J12.11 and J12.13 pins and run the following commands:

stty -F /dev/ttymxc2 -echo -onlcr 115200
cat /dev/ttymxc2 &
echo hello > /dev/ttymxc2

For each invocation of echo command the "hello" string should appear on the terminal.

Disabling UART2

To disable UART2 edit arch/arm64/boot/dts/freescale/fsl-imx8mm-var-dart.dts under kernel source directory and modify

&uart2 {
        ...
        status = "okay";
};

to

&uart2 {
        ...
        status = "disabled";
};

Other UARTs can be disabled in the same manner.