[MinnowBoard] Need to disable both UART on LSE?

[Wei, David]

>From below error message, I assume you were trying to sue GPIO 74 on GPIO controller INT33FC.  
Actually this GPIO does NOT connect to Pin12 of MinnowBoard Max Low Speed Expander. It actually connects to pin 19 of MinnowBoard Max Low Speed Expander, which is shared by GPIO_S0_SC[074] and SIO_UART2_RXD. 
So that's why you have to disable UART2 to get this GPIO work.

Pin 12 of LSE is connected to SIO_UART1_RTS# (or GPIO_S0_SC[072] ). It is GPIO 72 of GPIO controller INT33FC. 


[   11.943332] byt_gpio INT33FC:00: pin 74 cannot be used as GPIO.
-bash: echo: write error: Invalid argument

Thanks,
David | SSG BIOS






-----Original Message-----
From: elinux-MinnowBoard [mailto:elinux-minnowboard-bounces at lists.elinux.org] On Behalf Of Lucas De Marchi
Sent: Wednesday, April 29, 2015 6:28 AM
To: MinnowBoard Development and Community Discussion
Subject: [MinnowBoard] Need to disable both UART on LSE?

Hi,

Do I need to disable both UART1 and UART2 in UEFI in order to be able to use pin 12 in the LSE (GPIO_UART1_RTS)?  If I disable only UART1 I still can't use it:

[root at localhost ~]# echo 484 > /sys/class/gpio/export
[   11.943332] byt_gpio INT33FC:00: pin 74 cannot be used as GPIO.
-bash: echo: write error: Invalid argument

Pin 10 works fine though.

The only way I'm able to use pin 12 as GPIO is if I disable both UART1
*and* UART2.

Also I'm surprised I actually have to disable any of them since pin 12 is RTS. Wouldn't it be sufficient to disable flow control?

Here I have kernel 3.19.5 and firmware 0.77.  I also tried updating to
0.79 with no difference in behavior.


thanks

--
Lucas De Marchi
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