Using one connector for serial and programming (ISP)

[JimmyMoore]

I am trying to make a minimum pin count connector for both in-system programming and serial comm. I think it should work.

If I tie RXD with SCLK (RB7), those will always be inputs.

Since SDAT is bidirectional, I have to take TXD out and put it through a diode to SDAT (wire-ORing) it.

Also, what about the power requirements. If the ICD pod is powered by the USB, and my Unit Under Test is powered by its own power supply, I only need 1 ground wire on the interface, right?

Oh, and I would still need MCLR/VPP from the ICD and use High VOltage programming.

In the end my connector would be:
GND
MCLR/VPP
SCLK/RXD
SDAT/TXD
and it would cost me a diode from TXD to SDAT.

Has anyone ever tried this?



Thanks Much,
Jimmy

[crystal_lattice]

Why not use bootloader?? Min 3 connections: 1. Tx, 2. Rx, 3. Gnd Max 4(or more for more funtions): 4.Vcc This can be used to power your 232 level converter in you cable.

Kind Regards