[yocto] [meta-raspberrypi] Issue with 8250/16550 UART1 access in raspberrypi (meta-raspberrypi)

Andreas Enbacka andreas.enbacka at gasera.fi
Thu Jun 4 05:41:41 PDT 2015


Hello Valentin,

I used the wiringPi library to put the pins into the alternative mode. 

Regards,
Andreas

> 4 jun 2015 kl. 15:31 skrev Valentin Le bescond <valentin.lebescond at gmail.com>:
> 
> Hi !
> 
> I'm really no expert but am very interested in the subject.
> 
> Did you modify the device tree ? From what I understand in the DT that you'll find pinmux definition right ?
> 
> Regards.
> 
> 
> 2015-06-04 14:01 GMT+02:00 Andreas Enbacka <andreas.enbacka at gasera.fi>:
>> Hello,
>> 
>>  
>> 
>> After a long break, I have returned to the Yocto project, and generally very pleased. A lot of progress has been done since I last used the project (two years ago), and now in my opinion everything works very smoothly.
>> 
>>  
>> 
>> I have used yocto to build a custom image for the RaspberryPi Compute Module. Generally everything works ok, however I am experiencing problem with accessing the UART1 port on the raspberryPi. I am using a library called wiringPi to put the appropriate GPIO pins in the correct mode (alt5) for RXD1/TXD1 (pins 32/33). Also I have used menuconfig to enable the 8250/16550 serial port support in the kernel (3.18.5+). After booting the image I examined the dmesg output, and it shows following information related to 8250/16550:
>> 
>> ..
>> 
>> [   1.010958] Serial: 8250/16550 driver, 4 ports, IRQ sharing disabled
>> 
>> [   1.013920] serial8250.0: ttyS0 at MMIO 0x20215040 (irq = 29, base_baud = 7812500) is a 8250
>> 
>>>> 
>>  
>> 
>> Then I put the pins 32/33 into alternative mode alt5, and try to connect to the port /dev/ttyS0 using minicom (baud 115200). Trying to enter something into the Mincom terminal does not give any indications on our connected oscilloscope (connected to the relevant pins), however change of the alt mode earlier was observed correctly. The serial port should not be using any flow control, but when trying to disable the flow control using Minicom (it was on by default) freezes the complete RaspberryPi system (requiring to disconnect and reconnect power).
>> 
>>  
>> 
>> Does anyone have any thoughts what could be the cause of these issues (e.g., problems with driver etc)? Any information would be greatly appreciated. In the project we are working on we would need to use both uart ports (0/1) provided by the compute module (the uart0 is a pl011 and by disabling console use of /dev/ttyAMA0 we were able to successfully connect to that port).
>> 
>>  
>> 
>> Thanks for the great work with the Yocto platform.
>> 
>>  
>> 
>> Sincerely,
>> 
>> Andreas Enbacka
>> 
>> SW designer
>> 
>> Gasera Ltd
>> 
>>  
>> 
>> 
>> --
>> _______________________________________________
>> yocto mailing list
>> yocto at yoctoproject.org
>> https://lists.yoctoproject.org/listinfo/yocto
> 
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