[MinnowBoard] Problem booting with activity on I2S_FRM

[Anders, David]

Lucas,

Darren is correct that this is a boot strap pin, and I'd recommend using a different one if you are using it directly as a GPIO on startup, or else take care that it is not pulled low on reset...

Thanks
Dave Anders


-----Original Message-----
From: elinux-MinnowBoard [mailto:elinux-minnowboard-bounces at lists.elinux.org] On Behalf Of Darren Hart
Sent: Friday, March 27, 2015 6:45 PM
To: MinnowBoard Development and Community Discussion
Subject: Re: [MinnowBoard] Problem booting with activity on I2S_FRM



On 3/27/15 2:24 PM, Lucas De Marchi wrote:
> Hey,
> 
> I'm using the pin GPIO_I2S_FRM for gpio in my application. However 
> when I boot the board, if there's any activity on this pin already, 
> the board doens't boot. I get nothing on serial, not even the messages 
> from the bios. As far as I tested this is the only pin that exhibits 
> this behavior.
> 
> Firmware version is 0.78.  Is there anything that can be done to boot 
> the board even with activity on this pin?

Thank you for reporting this Lucas. I've looked into the design documents and that pin is also a strapping line which happens to select the BIOS boot:

0=LPC
1=SPI

While there is a buffer/voltage-shifter between the LSE connector and the SoC, it is possible that a low signal to the LSE connector is causing the SoC side of the signal to be pulled low, overpowering the 10k strap pull-up, effectively telling the SoC to boot via LPC instead of SPI, causing the issue you describe.

Can you describe exactly what activity you have applied to this pin at boot?

--
Darren Hart
Intel Open Source Technology Center
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