PBP projects for R/C models

[Bruce]

Ken,

If you're working with PBP, you need to forget about anything you read for the Mikroe BASIC compiler. These are two totally different compilers.

Everything you need to know about PBP is in the PBP manual. What you don't understand, just ask about here.

[mackrackit]

Ken,

Have you been to this page?
http://www.melabs.com/resources/samples.htm

As for routines. I would say that just about every "command" listed in the PBP manual is a routine. ADCIN for example. The routine for reading the chip's ADC is built into that command.

Keep asking questions

[Kenjones1935]

This PWM exercise is designed just for what I have done.

http://www.melabs.com/resources/samples/pbp/hardpwm.bas

After loading the .hex into the RC car (carrying my PICkit2), hooking up another battery and connecting CCP1 to the electronic speed control, The wheels spin!!

Ain't technology grande!

Ken

[mackrackit]

COOL!!!
Another piece down!

Did you get Walter's PWM reading code to work?
If so then maybe now you can combine the two.

If incoming PWM is X then wheels turn sort of thing?

[Kenjones1935]

As I said, the wheels go round, but...

The wheels are not going round and round in the pattern I expected. In particular they only go backwards. The code claims to sweep from 20% to 80% cuty cycle.

SOOO, can I use my USB connection and PICkit 2 Logic and Analyze Tool to see what is actually happening?

Ken

[ScaleRobotics]

I believe you are using the PWM example here: http://www.melabs.com/resources/samples/pbp/hardpwm.bas

This is a PWM that is not supposed to work with RC servo's. It's wave form is different. It is used to dim LED's etc. I am a little surprised that it can turn the wheels at all. I have a scope to help me view wave forms. I have tried for a few minutes to see what the pickit's logic tool can do, but I have not had any success. I am pretty sure it is just a problem with the operator (me).

[rmteo]

This is what the program header says:

' PicBasic Pro Program to demonstrate hardware PWM.
' Output is a 1Khz signal with duty cycle sweeping
' from 20% to 80% once per second

Since the frequency is 1KHz, its period is 1mS. The duty cycle is sweeping from 20% to 80% therefore the pulse width is varying from 0.2mS to 0.8mS. There are 2 problems here. For R/C signals, the period should be 20mS or 50Hz. Second, the pulse width should be 1.5mS for neutral, 1.0mS for extreme left (or full reverse) and 2.0mS for extreme right (or full forward). So your car is responding to a very short pulse (even less than full reverse). You have to modify the values in the program to get it to do what you expect.

[Kenjones1935]

Thanks gang.

I came to much the same conclusion myself. I have been trying to figure out what exactly this PWM code does so that I can modify it meet the RC specs. The comments in the program are fairly clear. My first attempts have not worked but I am optimistic.

Interesting how rusty my brain has become.

Ken

[rmteo]

I gave you that info in post #44.

Since the frequency is 1KHz, its period is 1mS. The duty cycle is sweeping from 20% to 80% therefore the pulse width is varying from 0.2mS to 0.8mS. There are 2 problems here. For R/C signals, the period should be 20mS or 50Hz. Second, the pulse width should be 1.5mS for neutral, 1.0mS for extreme left (or full reverse) and 2.0mS for extreme right (or full forward). So your car is responding to a very short pulse (even less than full reverse). You have to modify the values in the program to get it to do what you expect.