Raspberry Pi Forums

joan

As you say there are two hardware PWM channels. You will have to use software PWM for any additional ESCs. Unless there is a RPIO module for PERL (n.b. RPIO, not RPi.GPIO).

joan

That appears to be a standard servo, not continuous rotation. You can quite easily check using pigpio. Start the daemon. sudo pigpiod Assuming you are using GPIO 4 (Broadcom numbering). Command the servo to -67.5 pigs s 4 1000 Command the servo to 0 pigs s 4 1500 Command the servo to +67.5 pigs s 4 ...

joan

You can't use a continuous rotation servo to do what you want without additional hardware.

Could you link to the specs of your servos?

joan

It's probably not sensible to connect two GPIO both set as outputs. If they have different levels that will be a short-circuit which will probably damage the GPIO and eventually the Pi.

joan

The servo angle depends on the pulse width. A pulse width of 1500 µs will be central. Generally increasing the pulse width by 10 µs will increase the angle by 1 degree, decreasing the pulse width by 10 µs will decrease the angle by 1 degree. Just adjust the software you are using to do the same. n.b...

joan

pressureValue = rawValue[1] << 16 | rawValue[1] << 8 | rawValue[1]

Is not right.

In effect if you read x you are setting the answer to 65536*x + 256*x + x

You should be fetching the low, middle, high byte as the Arduino code is doing.

joan

piscope is a C GTK application which uses pigpio and the GPIO.

Code at http://abyz.me.uk/rpi/pigpio/piscope.html or https://github.com/joan2937/piscope

joan

It's fine to power the transmitter from 5V. It's best to power the receiver from 3V3 or use a resistor divider (between the receiver output and the GPIO) if powering from 5V. Try http://abyz.me.uk/rpi/pigpio/examples.html#Python__433_py on the input (and/or the output). It will set a glitch filter o...

joan

The mode change will take say a microsecond (probably less, I haven't tested). The GPIO level will change more slowly as the voltage at the GPIO changes. It takes time for the current to leak away. I'd have thought microseconds rather than milliseconds though. I expect there is more capacitance in y...

joan

You have to write 8 bits. If the top 4 bits are significant (unlikely, read the device specs) you will need to read the register before hand to find the value of those bits and then include those bits in the ones you subsequently write to the register. Look up Python bit handling.

joan

I would log the data received and try to work out why the software does not work for those low values. Then you will be able to decide how the software needs to be changed (if it does).

joan

Test the GPIO with wiringPi's pintest or (my) pigpio's gpiotest.

joan

If you want jitter free over I2C perhaps a module based on the PCA9685? It's commonly used for servos but it can be used to generate 500Hz+.

joan

The PWM support from the hardware is output only. If you want to read PWM on any of the GPIO it will have to be done in software.

joan

Yes it is. However toggling a pin by writing to a device on the I2C bus will be subject to a lot of jitter.

joan

https://drive.google.com/file/d/1pk0iEY ... sp=sharing

The photo is not clear enough to follow the wiring.

joan

I2C is a bus. Multiple devices may be connected in parallel.

joan

There will be plenty of code example if you google raspberry pi and mcp3008 software. The MCP3008 is a 10-bit resolution ADC (Analogue to Digital converter). It compares the voltage reference (generally 3V3 if used with the Pi) against the voltage at an input pin and returns a value between 0 and 10...

joan

You can use multiple MCP3008, 4 is certainly possible. Each is connected in parallel to the SPI bus and each will have a dedicated GPIO for chip select. So you need four GPIO plus the three GPIO of the SPI bus (MOSI, MISO, SCLK).

joan

Why ask us to guess? Show us a wiring diagram and clear photos of the connections plus the software listing you actually used.

joan

This probably won't help you but I have a PCA9685 driver which allows for the pulses to be stopped (pulse width of 0).

http://abyz.me.uk/rpi/pigpio/examples.h ... PCA9685_py

joan

What is that code meant to do?

What device are you trying to control? Do you know what signal to send to that device to achieve that control?

joan

Have you updated wiringPi? There was a new version available from wiringpi.com for the Pi4B.

joan

Can we have a photo of the connections between the Pi and the devices?

I'd also try to sniff the traffic with

http://abyz.me.uk/rpi/pigpio/examples.h ... 2C_sniffer

All you need is I2C_sniffer.py

Change I2C_sniffer.sniffer(pi, 1, 0, False) to I2C_sniffer.sniffer(pi, 3, 2, False)

joan

http://abyz.me.uk/rpi/pigpio/piscope.html

http://abyz.me.uk/rpi/pigpio/examples.h ... monitor_py

To get accurate data the clock should be 100 kHz or less. However any frequency should show up.

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