Dragon Board 410C - UART

Hi All,

Dragon Board with UART1:
Getting error message “gbam_connect_work: Bam channel is not ready” Only TX is working
If i connect RX pin, The Board keeep sending junk data in TX:

Is there way to use UART0??
Ashok R

Hi @asokfair,

Are you trying to use the UART for connecting sensor devices?
The UART1 on the LC connector (pin 11 and 13) is assigned for the serial console for the USB-serial adapters.

To use UART0 on the LC connector, it is also described in the dtsi file.

Hi Akira,
Yes , i Used dev/ttyHSL0 file to read and write data in UART1 , similer way for UART0 which is the file i have to use?

Sure i will check about apq8016-sbc.dtsi

Ashok R

Hi @asokfair,

Are you using Android image on your DragonBoard410c?

I just confirmed that UARTs on Debian is following.
/dev/tty96B0 → ttyMSM1
/dev/tty96B1 → ttyMSM0

Let me try installing AOSP.

Hi Akira, I am using Android OS

I have been using UART0 on Android by connecting to pins 5 and 7. The file I used for UART0 is ttyHS0.

Hi @asokfair and @koerant,

I checked the UART1 and UART0 on Android.
The UART1 is /dev/ttyHSL0 and it is used for serial console and can not use it for connecting devices such as sensors. This is the kernel option passed to the kernel.

cmdline: console=ttyHSL0,115200,n8

The UART0 is /dev/ttyHS0 and it should be usable on pin5 and pin7 on LS connector.

Thank you for your comment, @koerant. :slight_smile:

Thanks Akira and Andries,

Let me try this UART0, and come back

Ashok R

Hi Akira & Andries,

I did not find ttyHS0 in my file system, ttyHS4 and tty are there

Hi @asokfair,

Probably we are using different AOSP image on DragonBoard.
Do you mind teaching me which AOSP image you are using?

There are several images.

This is latest Member build release 16.03.

This is Reference platform release 16.03.

Hi Akira,

I guess , i downloaded from here dragonboard410c_sdcard_install_android-99

Ashok R



one more thing im using fast boot mode to flash images

Android Built Version , is msm8916_64-userdebug 5.1.1 LMY47V99 test-keys

Hi @asokfair,

I just finished installing Vendor build 16.03.

[ro.build.description]: [msm8916_64-userdebug 5.1.1 LMY47V 99 test-keys]

I confirmed that the UART0 is /dev/ttyHS4 on this build.

Thank you for the question.

Hi Akira,

Is that UART0 is working for you? for me not working
UART1 is working partially on PIN GPIO4, GPIO5 , only i could receive data not able to send.
Also facing difficulty to read the ttyHSL0 file in android.

Ashok R

Hi @asokfair,

I finally started to understand your intention of all questions.

The /dev/ttyHSL0 (UART1) is assigned as a serial console so it is not usable for other purpose, like connecting sensors or devices. And would you mind teaching how you see only receiving data is working and sending data is not working?

For the /dev/ttyHS4 (UART0), it could be a bug.
I would really appreciate it if you could write all your step by step testing and validating procedure and error messages or symptoms to the bug tracking system.


Hi Akira,
You mean that UART0 is not working?
Actually i want to check one more thing here by Grounding the Signal CTS ?

ashok R

Hi @asokfair,

Are you connecting the Dragonboard to a UART device? If so, remember that the Dragonboard makes use of 1.8V logic and if you connect it to a UART device that makes use of 3.3V or 5V you will run into issues. It could explain why you are receiving data but unable to transmit data.

To accurately test the UART0 just connect the Rx and Tx pins together and check that whatever string you send is received back.

1 Like

Yeah, I’m using TI TXB0108 1.8v to 3.3v level converter

1 Like