[MinnowBoard] Problem booting with activity on I2S_FRM
Lucas De Marchi
lucas.de.marchi at gmail.com
Sat Mar 28 20:12:53 UTC 2015
On Fri, Mar 27, 2015 at 8:45 PM, Darren Hart <dvhart at linux.intel.com> wrote:
> On 3/27/15 2:24 PM, Lucas De Marchi wrote:
>> 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:
> 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.
Ah, that explains well the issue.
> Can you describe exactly what activity you have applied to this pin at boot?
In my application it's connected to one of the channels of an RC
receiver. So it's basically a PWM signal with short duty cycle. Being
mostly at 0 explains why it fails to boot.
I think the easiest thing to do is to disable PWM1 that I'm not using
and then start using that pin instead.
Lucas De Marchi
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