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Author Topic: Broken Serial Console (hardware issue) and fix.  (Read 2392 times)
mikenemat
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« on: April 19, 2009, 04:42:07 PM »

So my sheevaplug arrived with a broken console output. Everything else worked fine (I could see it boot and get an IP address from my router) and also channel A on the FTDI chip would connect fine to the JTAG debugger.

I did some investigation of the schematics and identified some possible locations where there may be an issue. I opened it up and found that the first 3 pins on the main CPU board's ribbon header connector going to the JTAG board were bridged at the back of the PCB where they were soldered. Some quick work with a soldering iron to resolder them everything was fixed. My console output (channel B) now works.

Anyone who has this same issue may want to consider disassembling their SheevaPlug to check this, although it may void your warranty so proceed at your own risk.
« Last Edit: April 19, 2009, 05:00:19 PM by mikenemat » Logged

Rabeeh Khoury
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« Reply #1 on: April 19, 2009, 10:04:55 PM »

I did some investigation of the schematics and identified some possible locations where there may be an issue. I opened it up and found that the first 3 pins on the main CPU board's ribbon header connector going to the JTAG board were bridged at the back of the PCB where they were soldered. Some quick work with a soldering iron to resolder them everything was fixed. My console output (channel B) now works.

So, what was broken? The soldered points on the board?
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mikenemat
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« Reply #2 on: April 19, 2009, 10:12:43 PM »

Yeah, the first 3 points for the ribbon header were bridged (shorted) with excess solder.
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HankScorpio
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« Reply #3 on: April 21, 2009, 12:49:11 AM »

Pins  J4 1-4 are all +3.3v
Pins  J5 1-4 are all +5v

Pins J4 1-3 are all GND
Pins J5 1-3 are all GND.

So the solder bridge should be OK. I suspect it was the Pins on the board that connects the flex cable to the motherboard.

I had a few problems with that. Heating the pins and pushing them down fixed it.

Did you pry off the flex cable connector board?
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