problem figuring out which pins are which on 7i52s

can someone explain why /TX0B and /TX3B are good (0v when linuxcnc is closed) but 1,2,4 and 5 have 4.6v when linuxcnc is closed? this doesnt make sense to me

Because TXB0 and TXB3 have enable pins and are disabled when LinuxCNC
is not running.

I would suggest using the TX pins that are in the desired state when LinuxCNC is not running and fixing the running output polarity in the hal file

(or using a output pin for a common drive enable if your drives have a enable input as most PWM drives have)

so in case of TX1B, i would have to write setp hm2_7i80.0.gpio.039.invert_output true ?

If the 7i52s is on the first connector, it would be on GPIO19

You should run mesaflash with the --readhmid option to get a pinout file for your
configuration if there is a question about GPIO pin mapping:

mesaflash --device 7i80hd --addr 10.10.10.10 --readhmid > mypins.txt


If you are using LinuxCNC 2.8 you can do this more cleanly
by inverting the PWM pin:

setp hm2_7i80.0.pwmgen.NN.out0.invert_output true

okay thank you

that kinda works but everytime i start up Linuxcnc the motor spools up for a split second, maybe i have to put a relay between the 7i52s pwm and the motor driver or probably use the sleep input but i dont know if it is the enable input. This is what the manual says:

SLP HIGH Inverted sleep input: This pin is pulled high by the driver board, enabling the driver by default; drive SLP low to put the motor driver into a low-power sleep mode.

Does low-power sleep mode mean disabled?

BTW its the Pololu G2 pwm Driver board

I would guess that sleep mode means disabled

Another option is disabling the primary servo power on the AC side
with a relay until linuxcnc is running

PCW wrote: Another option is disabling the primary servo power on the AC side
with a relay until linuxcnc is running

I always do this anyway. The main power relay is controlled by the LinuxCNC "machine on" output.