[James Newton]

The BOB PID is a very low cost, but quite capable, PID servo controller.

Serial and step / direction inputs.
- The serial interface, via any TTL to USB adapter, allows for easy tuning of the P.I.D. constants and setting options like the polarity of the output direction signal. It also supports a bootloader for future firmware updates and new abilities / optimisation.
- The step / direction input allows its use in any application where a standard servo driver was intended. There is a Pololu adapter cable to make plugging it into a RAMPS / GRBL or pretty much any other motion controller very easy.

Position input comes from a standard quadrature type position encoder connected to the motor shaft. Up to 73,000 edges per second or 18,000 lines per second are supported with the current 0.93 firmware. That supports up to 1,100 RPM with a 1000 line (4k quad) encoder, or well over 10,000 RPM with our 360 quad ENC1.

The output is PWM speed and direction suitable for any standard "H-Bridge" motor driver.

All the details are here:

techref.massmind.org/techref/io/SERVO/BOBPID.htm

Source code is here:
https://github.com/JamesNewton/BOBPID

Couple of videos of it working:

Small DC motor with HID encoder run by BOB PID
https://youtu.be/TjflUkI--Sw


Large DC motor with ENC1 run with BOB PID from RAMPS/Marlin.
https://youtu.be/rnwYqGB3bXw

[James Newton]

A customer tells me he has a motor driver that needs two separate PWM inputs... one telling the motor to go forward, and another telling it to go backwards. I've never heard of such a thing! Has anyone else seen that?

If so, the BOB PIC firmware should be able to support it as follows (Note: this code is NOT tested):

The P1C signal from the PIC on pin RC3 comes out to the A axis Direction line on the BOB PCB, so that can provide the second PWM output.

In
github.com/JamesNewton/BOBPID/blob/master/main.c

Update SetPWM to add the following to the start.

if (MOTOR_DIRECTION) { // could also use if (PIDOutput > 0) {
	PSTRCONbits.STRC = 1;	//drive the output to A DIR, RC3, P1C
	PSTRCONbits.STRD = 0;	//NOT to P1D, RC2
	}
else {
	PSTRCONbits.STRD = 1;	//steer the output to P1D, RC2
	PSTRCONbits.STRC = 0;	//NOT to A DIR, RC3, P1C
	}

In the main setup code, you will need to tris (tristate) RC3 as an output. Right after:

	TRISCbits.TRISC2 = 0;	// Set pin C2 1=input / 0=output motor PWM

Add:

	TRISCbits.TRISC3 = 0;	// Set pin C3 1=input / 0=output motor PWM2

If anyone needs that, I can add it fairly easily.