Using Hardware UART with only transmit (no RX)

[JamesW]

Hi folks,

I am running a PIC18F26J11-I/SO on a datalogging board equipped with a modem.

I am using the 2nd hardware UART for debug, and I have assigned the two programmable pins that correspond to PGC and PGD (Pins B6 and B7).

The system is working great all the while my RS232 debugger is connected, but once the system is running unplugged - it occasionally resets.

I believe this is due to the pin that I have assigned as the RS232 input not being tied to anything and getting RF interference and resetting the processor. (This is pin B7).

Now...
As the pins are also PGC and PGD, I don't think I can get away with a pull-up/down as this will effect the programming ability. (If this is possible can you please let me know?)

In an ideal world I would like to have the hardware uart enabled, but only for the transmission of data (ie no RX pin)- That way I can assign the other pin as an output and force it low. However I can't see how to do this, as the RS232 definitions require both pins - likewise the routines to setup the uart, override the tris settings!

Can anyone please offer any advice?

Thanks in advance

James

[Ttelmah]

Are you actually using LVP?.

If you are, you can't have the UART on the same pins.
If not, then the RX pin needs to be biased to 3.3v, when not in use.

The programmer will connect to MCLR. What is on this when it isn't connected?.

Best Wishes

[JamesW]

I don't believe I'm using LVP - the board is SMT and I am programming it using the CCS U-64 programmer.

There is also no mention of LVP in the fuse settings for this particular device.

Cheers

James