Using UART1 for terminal communication

microtech

Hi, I'd like to use UART1 instead of UART0 for console access.

I have a custom board based on the am335x EVM. The UART0 connections were pinmuxed to SPI1 based on the available SPI connections. So, the serial port was connected to UART1. I have board jumpers that let me connect up to UART0 to see that everything is booting using UART0. I am having trouble getting the code switched over to use UART1 instead of UART0. I'd like to get everything switched over: U-Boot, kernel, linux login. I've tried modifying a few files and configurations without much luck. It still tries to use UART0 or doesn't work at all.

What do I need to do to use UART1 for each of these boot processes?

Thanks,

Alex

over 11 years ago

0 Miroslav Kiradzhiyski XID over 11 years ago

TI__Mastermind 25235 points

Hi,

Changing the serial console to another serial port is done in the following way:

* U-Boot:
Compile U-Boot with the following command: make am335x_evm_uart2

* Kernel:
Add the following in the U-Boot bootargs and pass it to the kernel at boot time: console=ttyO2,115200n8

* User space:
Modify the /etc/inittab file with the following:
S:2345:respawn:/sbin/getty 115200 ttyO2

Best regards,
Miroslav

0 microtech over 11 years ago in reply to Miroslav Kiradzhiyski XID

Prodigy 190 points

Thanks for your reply. I've modified the u-boot using: make am335x_evm_uart1. I'm not seeing output on UART1. The console output on UART0 gets to the line "reading u-boot.img" and stops. My first thought is that it's switching to UART1 and I don't see the u-boot output for some reason but it never returns to UART0 to output as the kernel loads. I switched back to u-boot with UART0 and it boots fully.

Is there any other changes I need to make to enable UART1?

I've reviewed the board schematics and UART1 is connected similar to UART0 and both use default MODE0 pinmux for Tx/Rx. A difference is that my UART1 doesn't use RTS/CTS connections. The UART1 RTS/CTS connections are connected to other GPIO functions.

Thanks,

Alex

0 Miroslav Kiradzhiyski XID over 11 years ago in reply to microtech

TI__Mastermind 25235 points

Did you change the MLO file as well as the u-boot.img?

Do you have anything else connected to UART1?

Can you try this with UART2 for example?

Best regards,
Miroslav

0 Biser Gatchev-XID over 11 years ago in reply to Miroslav Kiradzhiyski XID

TI__Guru**** 393215 points

Hi,

Is UART1 connected to anything else on your board? On the GP EVM you need to remove R354 and R356, and place 0Ohm resistors on R232 and R236 to get UART1 routed out to the RS-232 connector.

0 microtech over 11 years ago in reply to Miroslav Kiradzhiyski XID

Prodigy 190 points

Did you change the MLO file as well as the u-boot.img?

This was the problem. I was only changing the u-boot.img and not both files.

Thanks for your help!

0 Vijaykumar Ponugoti over 10 years ago in reply to microtech

Intellectual 550 points

Hi,
May I know how can I change MLO file? I thought make configfile builds both uboot as well as MLO. Isn't it.?

Rgds,
Vijaykumar P

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Using UART1 for terminal communication