I've been trying to interface a Mitutoyo digital caliper. I used the code from here and I think I made the right corrections according to the posters comments but as I checked he was last online in 2017.

I connected my raspberry according to the image below, with DATA going to GPIO2, CLK going to GPIO3 and REQ going to pin 4. Also I connected the GND from the cable to the ground on the raspberry (don't know if that made a difference. When I ran the code no error happened but I also got nothing to print enter image description here

#!/usr/bin/env python

# SPC.py
# 2016-12-04
# Public Domain

import time
import pigpio


# The callback implements the Mitutoyo SPC protocol
# 13 4-bit nibbles, least significant bit first.

def cbf(gpio, level, tick):
   global in_data, bit, nibble, nibbles, data_level
   if gpio == REQ:
      nibble = 0
      bit = 0
      nibbles = [0]*13
      in_data = True
   elif gpio == DATA:
      data_level = level
   else: # CLK
      if in_data:
         nibbles[nibble] |= (data_level << bit)
         bit += 1
         if bit > 3:
            bit = 0
            nibble += 1
            if nibble > 12:
               in_data = False

pi = pigpio.pi()
if not pi.connected:

in_data = False
bit = 0
nibble = 0
nibbles = [0]*13
data_level = pi.read(DATA)

pi.set_mode(REQ, pigpio.OUTPUT)
pi.write(REQ, 1)
pi.set_pull_up_down(CLK, pigpio.PUD_UP)
pi.set_pull_up_down(DATA, pigpio.PUD_UP)
cb1 = pi.callback(REQ, pigpio.FALLING_EDGE, cbf)
cb2 = pi.callback(CLK, pigpio.FALLING_EDGE, cbf)
cb3 = pi.callback(DATA, pigpio.EITHER_EDGE, cbf)



  • Check to see the actual data with abyz.me.uk/rpi/pigpio/piscope.html – joan Jan 12 '20 at 17:07
  • Checked the data, then used a sample program that turns morse code into signals to check if the piscope works and it does. When I run the actual program, all the pins get set to 1 and then it just waits for 300s and quits. – Tilen Pintarič Jan 12 '20 at 18:29
  • We would be guessing about what is wrong. You will have to experiment as the software can't produce a reading while there is no data. Clear photo(s) of the connections between the Pi and the sensor may help. – joan Jan 12 '20 at 18:34
  • link Here are the pictures, nothing too complex. – Tilen Pintarič Jan 12 '20 at 18:58
  • You need to add any additional information to your question. – joan Jan 12 '20 at 20:00

Welcome, Tilen. I can't see that nibble will ever be >12 - don't forget you're starting from zero and reading 13 bits... This might explain why you're not getting any output...

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