M62, M63, M64, M65 & M67 User I O Commands - bdring/Grbl_Esp32 GitHub Wiki

User I/O Commands

This feature is for generic I/O (output) control. You could use it for cooling fans, clamping, valves, etc. The pins could be digital (on/off) or analog (PWM). It allows you to control the pins with gcode rather than special coding.

Synchronization

Synchronized means all motion in the buffers must complete before the I/O is changed. Immediate does not wait and acts upon the command as soon as it is read.

With streaming gcode, you should use the synchronized commands. There is no timing guarantee with immediate versions of the commands.

Types

Digital I/O
Analog (PWM)

Commands

M62 - M65 Digital Output Control

M62 Synchronized Digital Output On

M63 Synchronized Digital Output Off

M64 Immediate Digital Output On

M65 Immediate Digital Output Off

Use P word to indicate digital output number (0-3)

Examples:

M62 P0  // turn digital pin 0 on
M63 P0  // turn digital pin 0 off

M67 - M68 Analog Output Control

M67 Synchronized Set Analog Value

M68 Immediate Set Analog Value

Use E word for analog output number (0-3)

Use Q word for analog value in percent duty.

Examples

M67 E1 Q23.87 (set set output#1 to 23.87% duty)
M67 E1 Q0 (to turn off the pin. 0% duty)

Pin Numbering

There are 4 pins for each type, numbered 0 to 3. The numbers for the digital and analog are independent. If you use one of each, they could both be 0.

Special Behaviors

Power On - All pins will be set to the off state
Reset - All pins will be set to the off state
Alarm Mode - No change in pin state
Error - No change in pins state
End of File - No change in pins state

Setup

#define USER_DIGITAL_PIN_0   GPIO_NUM_xx
#define USER_DIGITAL_PIN_1   GPIO_NUM_xx
#define USER_DIGITAL_PIN_2   GPIO_NUM_xx
#define USER_DIGITAL_PIN_3   GPIO_NUM_xx

#define USER_ANALOG_PIN_0      GPIO_NUM_xx
#define USER_ANALOG_PIN_1      GPIO_NUM_xx
#define USER_ANALOG_PIN_2      GPIO_NUM_xx
#define USER_ANALOG_PIN_3      GPIO_NUM_xx

#define USER_ANALOG_PIN_1_FREQ      50  // Hz

Analog Frequency

Defining a frequency is optional. If you do not define one for a pin the default of 5000Hz will be used.

Analog Resolution

The resolution is dependent on the frequency used. The PWM is based on a 80MHz timer. If you have a 10KHz frequency, 80,000,000 / 10,000 gives you a maximum of an 8,000 count resolution. The resolution is based on bits, so you need to round down to the nearest bit value which would be 12 bit or 4096. The highest bit value allowed is 13 bits.

This is all done behind the scenes to give the highest resolution, you only have to provide the frequency (optional) and duty.

Analog Duty

The duty is a percentage of the period. It you are looking for a specific pulse width, you need to determine the period, which is 1/freq. If your frequency is 100Hz your period is 10ms. If you want a 1ms pulse, you would set the duty to 0.10%. Duty is a floating point number. A value of XX.XX will get you the highest resolution. Values above 100% are set at 100%. Negative numbers are set to 0%.

Use With RC Servos

RC Servos set their position based on the pulse length of a PWM signal. The standard frequency for RC servos PWM is 50Hz, some digital servos can handle a higher rate, but it will not improve performance in this application and it could overheat some servos.

The standard pulse range for RC servos is 1ms to 2ms. Some servos have a wider range.

With a 50Hz frequency the period is 20ms. Therefore a 1ms pulse is 5.00% duty and a 2ms pulse is 10.00% duty. Use the 2 values to to go from one end of travel to the other. You can use values in between to go to other positions. You can experiment with a little less or more if you servos have a bigger range. Servos do not have great resolution, so small changes in the duty may not affect position.

You can also set the duty to 0%. This generally turns a servo off and allows it to free wheel and not draw much power.

The servo will move as fast as it can to the target. The next gcode will occur right away. If you need to wait for the servo to move, you should add a G4 Px.xx command.