About Serial Console Port of Bubblegum-96 Board


I have two Bubblegum-96 at hand, both of their seial console did’t work! I checked the latest schematic v1.0 at this link:https://raw.githubusercontent.com/96boards/documentation/master/bubblegum-96/Schematics_Bubblegum96.pdf, it has a circut at page 17 that the 1.8V GPIOD1/UART2_TX and GPIOD0/UART2_RX convert to 3.0V debug port, that’s TP6~TP12 on bottom side of the board. But nothing can i see from this port! I don’t know what’s wrong with it! I searched on Baidu, Google, nothing about this issue! It seems that few people use this board currently. And I found a file in the SDK, S900_sdk/owl/s900/boards/android/s900_96board/bootloader.ini, in this file, I found a section defined the serial port:
;uart_id:uart index
;uart_pad:which pin the uart_id used
;uart_baudrate:the serial’s baudrate
In this section “uart_pad” is totally confused me! The comment is so LOW, you know, I can’t catch what the hell is “which pin the uart_id used”, if it point to the PIN of S900, then uart_pad equals an interger, are you kidding me!

Then I search all the documents in the SDK, nothing more about this god damn uart_pad!

So, please help me!
I want to change the uart_id TO UART2, BUT i don’t know how to define the god damn uart_pad! The guy who give this comment should be fired! Even i found a table , but i can’t stll determine the value of uart_pad!

Please help!


Somebody, help, please!



why would you like to switch to UART2? I think your intention here is to get serial console up
so, just stick to uart5…
btw, do you have problem to connect the hardware…


I have take a close look at the schematic at page 17, so you should try to connect your serial port to UART 5
which is [PIN11 GPIOA27/UART5_TX] & [PIN13 GPIOA25/UART5_RX]
and set to 115200n8

wish you good luck!


I just want to find out how to change the serial console to another uart port. The definition of uart_pad confused me a lot. It’s really rather hard to understand such definition. I found a table in Page-30 of file <ActDuino S900_板型配置說明_V1.0.pdf> , which is uart配置表. Please tell me how to define a different serial console according to this table.
For the reason i can’t use UART5 is that I don’t have a serial convert board at hand and the IO voltage of uart5 is 1.8V. But the UART2 transfer to 3.0V via an on board chip. So, please explain the defination of uart_pad. Please.
The board version is v1.0. So, the newest debug port is no longer UART5, but UART2 on board(see Page17 of schematic). If i still use uart5 , i will need a converter board. Why I can’t paste picture here???

One more important thing , change a serial console should be very very very very simple, as simple as ABC, but it caused me a lot of time to find it out. And still nothing worked. Why? The documentation is so so so rubbish. It’s not mankind readable.


for using UART2 which the pins are GPIOD1/UART2_TX/OEN , GPIOD0/UART2_RX/OEP …

I think, bootloader.ini is only used by bootloader (u-boot).
uart_id=2 # -> using the UART2
uart_pad= ?# -> using which PAD , need map to GPIOD0, 1, hanen’t found out this info

for kernel, try to adjust device tree info, by default it already configure PIN GPIOD0, 1 as UART2
— a/arch/arm64/boot/dts/s900_96board.dts
+++ b/arch/arm64/boot/dts/s900_96board.dts
@@ -29,7 +29,7 @@
compatible = “actions,s900”, “actions,s900-evb”;

    chosen {
  •           bootargs="fb_logo_reserve=0x19000000,0x03000000 console=ttyS5,115200 earlyprintk=serial-owl,0xe012a000 no_console_suspend loglevel=4";
  •           bootargs="fb_logo_reserve=0x19000000,0x03000000 console=ttyS2,115200 earlyprintk=serial-owl,0xe012a000 no_console_suspend loglevel=4";
      memory@00000000 {

@@ -368,6 +368,10 @@

  •   serial2: uart@e0124000 {
  •           status = "okay";
  •   };


I gave up using the Actions CPU in my project. I can’t found any other chips that worst than Action in this world!


Where can i find the S900 SDK?