PBP projects for R/C models

[Kenjones1935]

Bed time here on the east coast.

I tried both
OSCCON = %01110111
and
OSCCON = %01110001

I got the PIC to read the PWM signal from the radio channel 3 by doubling the threshold for differentiation. I can toggle between PIC and radio control.

But I have not been able to get the HPWM to behave. I tried using the original duty cycle. This made the wheels go backwards very fast no matter what was in the HPWM command. I tried doubling the duty cycle (to account for cutting in half the clock rate and the wheels did not turn at all. The Electronic Speed Control wants this PWM signal to arrive at 50 hz. In fact it is probably at 489Hz (according to page 87 of MicroEngineering Labs' PICBASIC PRO book). I'll put a 'scope on it tomorrow.

I think the book says that HPWM channel, 127, 50 will be a square wave of 489Hz. Does that agree with you guys' thinking?

I also have not gotten the PING echos to mean anything. The little red lights on the SRF05s are blinking. But my code is not making sense of the echo responses. I thought that all I would need to do was to double the expected echo pulse duration numbers.
Ken

[Byte_Butcher]

Bed time here on the east coast.

I tried both
OSCCON = %01110111
and
OSCCON = %01110001

I got the PIC to read the PWM signal from the radio channel 3 by doubling the threshold for differentiation. I can toggle between PIC and radio control.

But I have not been able to get the HPWM to behave. I tried using the original duty cycle. This made the wheels go backwards very fast no matter what was in the HPWM command.

did you add :

DEFINE OSC 8

to your code somewhere near the top?
Otherwise the PIC thinks you're still running at the default 4MHz.


steve

[rmteo]

The Electronic Speed Control wants this PWM signal to arrive at 50 hz.

Ken

No matter how you cut it, to get 50Hz (20mS period) using hardware PWM, the maximum clock frequency you can use is 0.819MHz (819KHz)

[mackrackit]

Darn,
I thought the SRF05 was the same thing as the PING. Now I see that the SRF05 takes a different trigger pulse.

So it looks like I just wasted your time on that part.

I guess on the good side rmteo noticed another possible problem.

I wonder if a While/Wend loop using PWM would be the answer?

[Kenjones1935]

Originally Posted by Kenjones1935 View Post
The Electronic Speed Control wants this PWM signal to arrive at 50 hz.

I was not clear in my last posting. The Electronic Speed Control PWM specification is for a single positive pulse no less than 1ms and no more than 2ms once per 20 ms, ie 50 pulses per second. The one to two millisecond pulse width is divided into 256 parts. 1.5 ms corresponds to 128 which corresponds to neutral in a servo.

Neutral is steering straight on a steering servo. Neutral is stopped on a wheel driving servo.

I discovered that using HPWM with the 4mhz default oscillator a pulse width of 100 to 110 gets the behavior of 'neutral' on my car. For example "HPWM 1, 100, 50" turns the front wheels of my car to straight. See the attached picture. Channel 2 is the HPWM version of neutral. Channel 3 is what the radio receiver sends.

Ken

[Kenjones1935]

I have found a way to make short, 10 to 80 usec pulses while using the 4mhz oscillator. The SRF05 proximity detector wants at least 10 usec. If I give it super long pulses catching the following echo measurement can be a problem for PULSIN.

Sooo the following makes an 80 usec positive pulse.

SYMBOL trigright = PORTB.0
LOW trigright
HIGH trigright
HIGH trigright
HIGH trigright
LOW trigright.

One thing at a time.

Ken

[Kenjones1935]

I now have the sonic ping devices (SRF05's) flashing continuously. There is no blockage in the PIC's processing.

Now the car is reacting too quickly. There is a bit of code that used to guarantee a 1/2 second backing up when backing up was necessary. Now the count down for this delay is instantaneous. While turning a corner the proximity sensor data gets confusing. Both the side sensors and the forward sensors are hearing important echos. I might need to adjust the positions of the two SRF05's or write some code especially for that situation. I am not sure - elusive. Like I said.


Ken

[Ioannis]

Hope you are not activating both sensors at the same time, right? Be sure to give some time for the echo to decline enough before confusses the other sensor.

Ioannis