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Serial problems on p9/p10

Topic last updated 19 Oct 2011, by Wim Huiskamp. 2 replies
Michael Shimniok
18 Oct 2011

So... I think I fried my mbed's p9. :(

I've got a 4800bps 5V GPS hooked up to p9/p10 using a 1x4 pin header on the mbed side to a 1x6 pin header on the GPS side. TX/RX were working fine. I accidentally hooked up the GPS side backwards (stupid stupid stupid!) frying the GPS and connecting P9 and P10 to +5V. With an identical, replacement GPS, data in is fine unless p9 is connected at which point the data turns to gibberish. P9 doesn't turn on an LED using DigitalOut.

Intuitively +5V to p9 with UART going seems like it'd fry something.

I'm curious to learn what, at the silicon level, smoked?

Also... wondering if anyone's successfully swapped an LP1768 on the mbed... ?

Thanks, Michael

Michael Shimniok
19 Oct 2011

Interestingly, UART3, when used on p17 and p18, works just fine.

Wim Huiskamp
19 Oct 2011

It is possible that you have only damaged the port I/O electronics and that the UART behind it is still OK. Try using one of the other input/output functions that are available on p9/p10 to see if they still work (e.g. DigitalOut/In or I2C).