help please CCP for Duty cycle measurements on PIC24!!

JamesW · Joined: 23 Apr 2007 Posts: 91 Location: Rochester, England

Hi folks

I've been using pic's since the mid 90's but up to this point have never needed to use CCP to measure anything.

I've now got an application using a PIC24FJ64GA306-I/PT (running at 32Mhz), where I am connected to a Digi 868 wireless module & loads of peripherals.

I need to monitor the signal strength of the wireless, and the module provides a PWM signal with a period of about 72uS to allow you to monitor this.

I've set it up on pin B8, using timer1 and had a go at it, and despite two of us ending up tinkering with it have got absolutely nowhere sensible! (And the code has got more and more complicated and messed up).

I've got quite a few other sources of interrupt, and the unit is pretty busy (and to be honsest, the only thing I am going to be using the signal strength for is a number on the LCD display)

All I really need is a percentage number, to reflect how good the strength currently is.

Given the above details - can anyone please explain how to it simply (it's been a long week!)

Thanks in advance

James

Mike Walne · Joined: 19 Feb 2004 Posts: 1785 Location: Boston Spa UK

What happens if you measure the mean voltage?

Mike

temtronic · Posted: Fri Sep 16, 2016 6:51 pm

Honestly, I'd start 'fresh'. Simply cut code to measure the PWM signal and display on a local LCD (if your project has one) or send to PC terminal program. For test purposes I'd use a 2nd PIC as the PWM signal, that way YOU can control the 'signal strength', maybe 3 buttons for 25, 50, 75us.
You need to eliminate all the other stuff and concentrate on the PWM capture and display. Once that works THEN integrate the code into your main program.

Jay

newguy · Joined: 24 Jun 2004 Posts: 1907

Ttelmah · Joined: 11 Mar 2010 Posts: 19498

I have to say, stop.....

Look at the paperwork for these units:

JamesW · Joined: 23 Apr 2007 Posts: 91 Location: Rochester, England

Sorry for the delay in replying folks, I enabled the PWM output - fed it through an RC network, and am getting an analogue signal that is measureable/useable - thanks for the advice.

I also believe I got to the bottom of why the CCP wasn't working as planned, as the CCS Modbus code/driver (being used to talk to a sensor in the background) uses the same timer interrupt - but buries it deep down in the driver code, so it's not immediately apparent that the timer is enabled, interrupting and in use.

With regards to the xbee PRO 868's, I'm not using these - but rather the XBee 868LP's instead, which are not end of life.

Thanks for all the help

James