sharing pic programming pins

Will Reeve · Joined: 30 Oct 2003 Posts: 209 Location: Norfolk, England

Stuck! I am trying out a PIC18F20K80 and it's PGD and PGC are shared with TX2 and RX2 which I need to use! I've shared PGD and PGC with buttons before (not a problem as they are usually contact closure to GND).

TX2 and RX2 will be connect to a FT232 USB UART. TX2 will be OK as the UART has an input connected to that pin, not ideal but will just receive the programming clock.

However RX2 will be connected to the output of the FT223.
I am thinking a 47k resistor should do it allowing ICD control over PGD and when it's not connected the output of the FT223 can drive OK.

Any better ideas much appreciated.

bkamen · Posted: Mon May 23, 2011 3:33 pm

If you look at the topics concerning ICSP from Microchip, they use smaller resistors (about 10K) but engage the same concept.

The ICSP hooks directly to PGC/PGD and the 10K's hook up to your other I/O.

I just did this recently with a 46J11 hooked to stuff on PGC/PGD.

-Ben
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Dazed and confused? I don't think so. Just "plain lost" will do. :D