CCCCCCC's Debug serial port output on unsuccessful boot

[Matt99eo]

Working with a BBB that has a custom hardware cape on it.

Sometimes I get an unsuccessful boot out of it where when connected to the serial debug part I see the letter C printed indefinitely.

I'd say 90% of the boot attempts work (serial debug looks normal) and 10% I get the infinite C printout and no successful boot. 


Any ideas?

[Gerald Coley]

Your cape is screwing up the boot pins. The processor cannot find a valid boot source based on what it reads from those pins.

Gerald

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Gerald

 

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[CEinTX]

I have seen this too.

It is as Gerald says. Your cape is loading one or more of the boot pins.

I did a cape - even though all the connections were high impedance inputs,

it was still enough to twitch the boot pins. Anyway, I ended up adjusting a couple

of the pullup  resistors to adjust for it on the pins I was using - changed from 100k to

33k. Only had to do this for the pullups - so apparently stealing even a little from the

33uA max source was enough to impact the boot read of the pins.

Hope that helps.

GL

Matt

[Matt99eo]

Ok Thanks guys,

Identified and fixed the effected pin and now getting consistent boots.

Cheers,