PIC24EP512GP806 - PMD register question

[benoitstjean]

Device: PIC24EP512GP806
Compiler: 5.026 (all of a sudden my 5.116 version no longer opens for some reason)

Hi guys,

Its been a while since I posted here and this pertains to a piece of code written a long time ago and I'm just curious about the behavior.

I believe this was actually TTelmah who had given it to me.

Basically, my device goes to sleep and the following code is called:

[gaugeguy]

Before you initialize the I2C module (or any other module you want to use) you need to turn it back on in the appropriate PMD location. The data sheet will detail which bits disable/enable which peripheral.

[benoitstjean]

Actually, I may have just realized that I may be confused:

1) I call getenv(), print-out the value;
2) I set all the values to 0xFF then I print them again without calling getenv() and the values are the same;

Unit goes to sleep.
-wait-
Unit wakes-up.

Then I don't call getenv(), I simply print the values again and they are again the same.

So I guess I'm really confused as to how I should be getting/setting values.

[gaugeguy]

Read section 10 of the data sheet on Peripheral Module Disable. specifically 10.4 and 10.6

Your existing code is also suspect as the PMD registers are 16 bit and your code is treating them as 8-bit.

[benoitstjean]

Oh yeah, good catch on that one but I'm still trying to wrap my head around the usage of getenv and setting these value registers. This code has been there for years and I never looked back at it....


I changed #byte to #word just to see if it would maybe change something but it does not...

[benoitstjean]

UPDATE: So I've commented-out all the code pertaining to PMD registers and after waking-up from sleep, I2C is still off because my sensors aren't working contrary to when I do a real power-up.

In all honesty, I have no idea how the use the getenv() function for what I want to do and CCS docs, well, it's CCS docs. It's good for what it's worth.

The problem here is that I know what my end goal is, I just don't know how to achieve it. I've looked at section 10.4 and 10.6 of the PIC manual and that's all nice and fine but it doesn't explain how to do what I want to do using the CCS compiler.

So:

1) How do I use getenv() to get/read the current status of PMD registers (so that I can set each PMD register back to these values upon waking-up);

2) How do I disable all PMD registers to save on power;

3) When the MCU wakes-up, how do I set-back all PMD registers to the same states as they were before going to sleep;

4) How do I confirm that what I've set the PMD registers to has worked (using just an fprintf is fine);

5) How do I force I2C to be up and running after waking-up from sleep, if that has anything to do with the PMD registers;


Thanks again and sorry for the confusion.

Ben