RasPi 2B: control 2 motors simult. by ident. pwm: how to?

[davenull]

hello,
with my Raspi 2B I need to control at least 2 motors simultaneously by identical pwm (plugged to a L298 H Bridge), but I could find only 1 pwm pin on the GPIO header:
how to do it then?

[Laurens-wuyts]

Does it need to be the same PWM?
If so, you could connect 1 PWM output to the 2 inputs on the H-bridge.
If not, you could make software PWM (I think it's available in pigpio) for every pin.

Laurens

[BMS Doug]

PIGPIO will give you hardware timed PWM on any GPIO pin.

[PiGraham]

PIGPIO will give you hardware timed PWM on any GPIO pin.

I like pigpio.
Other DMA based gpio libraries can also provide stable PWM on any pin. AFAIK WiringPi and ServoBlaster can also do that.

[BMS Doug]

PIGPIO will give you hardware timed PWM on any GPIO pin.

I like pigpio.
Other DMA based gpio libraries can also provide stable PWM on any pin. AFAIK WiringPi and ServoBlaster can also do that.

I've heard that they can, I only have experience of gettingPWM working with PIGPIO, I've never tried servoblaster and not tried PWM with WiringPi.

[davenull]

@ Laurens: there will be 2 different pwm signals needed, for a robot differential drive.

@ all: I am currently fine with pwm frequencies on my Arduinos so far (via analogWrite(0-255) - not quite sure, something like 1-4 kHz perhaps)
- which frequency/resolution will provide pigpio (or wiringPi )?

[BMS Doug]

@ Laurens: there will be 2 different pwm signals needed, for a robot differential drive.

@ Doug: I am currently fine with pwm frequencies on my Arduinos so far (via analogWrite(0-255) - not quite sure, something like 1-4 kHz perhaps)
- which frequency/resolution will provide pigpio (or wiringPi )?

Have a read of the PIGPIO documentation but as I read it you can set the PWM rate up to 40000Hz and achieve up to 20000 step resolution.

I'm sure Joan will be along to correct any errors I have made.

[davenull]

thank you for your link to the pigpio documentation - but that's not understandable to me, far too mauch information, I'm an absolute beginner to Raspi.
I am simply used to commands like
analogWrite(uint8_t pwm)

For the start I need no different settings, I just need to know about the default pwm frequency setting.

I had a look to wiringPi before, here a similar command is available like for the Arduino API, but I also don't see informations about pwm frequencies....

[joan]

Why not use Python? The PWM is the same.

pigpio defaults to 800Hz frequency with a dutycycle between 0 (off) and 255 (fully on).

From C gpioPWM

From Python set_PWM_dutycycle

[davenull]

thank you very much, yes, I think 800 Hz will be fine, and I am using C (actually g++) !

BTW,
as you are the API author:
will pigpio be compatible then when I am also using wiringPi API functions for different purposes (not pwm) in the same program, simultaneously?
(e.g., delay, digitalWrite, analogRead, wiringSerial ?)

[joan]

thank you very much, yes, I think 800 Hz will be fine, and I am using C (actually g++) !

BTW,
as you are the API author:
will pigpio be compatible then when I am also using wiringPi API functions for different purposes (not pwm) in the same program, simultaneously?
(e.g., delay, digitalWrite, analogRead, wiringSerial ?)

Yes, pigpio is compatible with wiringPi.

However if all you are using is the PWM functions you would probably be better off using something like servoblaster or pi-blaster. They were designed for PWM.

[davenull]

no, it's not the only purpose, there will be many API functions I will use (and need) both from pigpio and from WiringPi then.
Thank you!