PIC24 set environment variable [SOLVED]

[benoitstjean]

Device: PIC24HJ256GPxxx
Compiler: 5.026

I am using a hardware UART #1 on my device.

The UART is tied to a serial modem.

To make the modem go into "sleep" mode (low-power), the modem's RX pin needs to be driven low.

Since I am using the HW UART, I cannot force the PIC's TX pin low by simply by calling output_low( PIN_x )... I've tried it and it doesn't work or shall I say, it doesn't let me do that (has no effect).

So, how would I access direct PIC registers to simply tell the PIC's TX pin to go low? And when I want to resume the modem from sleep, tell the PIC's TX pin to go high again using direct register access?

At the moment, I can call, let's say,

#word U1MODE = getenv("SFR:U1MODE");

to get the state of the U1MODE register bits.

So, how do I 1) force a bit low/high and 2) which bit(s) in which register is it?

Thanks,

Benoit

[newguy]

I think you have to disable/turn off the UART first, then you'll gain control of the RX/TX pins.

[benoitstjean]

Thanks newguy but that didn't answer my question. I realize that's what I have to do but I was asking *how* to do it.

Anyhow, I was able to figure it out:


To disable UART1 transmitter and make U1TX pin controlled by port: