Mitutoyo digital gauge reader sending values to a computer over Wi-Fi and USB for quality measurement work (in-house research)

How the brief came about

This reader sends values from a digital gauge directly to a computer, instead of someone reading the figures on the gauge display and typing each value into a program. Digital gauges already display results as numbers, but if they still have to be retyped, recording results remains slow and typing errors can occur.

Many Mitutoyo digital gauge models, such as vernier calipers and micrometers, already have a Digimatic port for sending data. This prototype therefore starts by receiving values at that port. This work was our in-house research and development in 2015–2018.

Requirements and constraints

The prototype's documents do not record requirements as a separate list. The requirements below are summarised from what the prototype's code and manuals actually do.

• Read values from the gauge through the Digimatic port's signal pins: the clock pin (CLK), data pin (DAT) and request pin (REQ)
• Send values to the program open on the computer, followed by Enter, so that the next field is ready for input
• In the Wi-Fi version and keyboard mode, the person measuring triggers the send themselves by pressing the foot switch or a button
• Limitations: the modes that send values through the serial port need a program on the computer side to receive them, and keyboard mode takes values from one gauge at a time

How do sending values over Wi-Fi and over USB differ?

The Wi-Fi version requires the Gauge Reader program to be installed and open on the computer to receive values. The USB board in keyboard mode needs no additional software, because the computer sees the board as a keyboard. Both the Wi-Fi version and keyboard mode type values into the open program, followed by Enter, when the person measuring triggers the send.

How does the USB board work in keyboard mode?

1. 1

   Connect the gauge to the board

   Run a cable from the gauge's Digimatic port to the ATmega32U4 chip board, then plug the board into a USB port on the computer.

2. 2

   The computer sees the board as a keyboard

   The firmware in keyboard mode (USB HID) makes the computer recognise the board as a keyboard.

3. 3

   Press the button to send a value

   When the person measuring presses the button, the board types the gauge value into the field where the cursor is, then presses Enter automatically.

4. 4

   Use with programs that accept typing

   Values go into any program that accepts keyboard typing, such as a table in a spreadsheet program or a measurement recording form.

The v3 firmware has 2 further modes that send values through the serial port: sending when the computer requests it, and sending as soon as a value is read. These 2 modes both support up to 4 gauge channels but need a program on the computer side to receive the values.

How does the Wi-Fi reader on the NodeMCU board work?

1. Connect the gauge and foot switch to the reader on the NodeMCU board
2. Set the Wi-Fi name and password and the destination computer's address through the reader's settings web page
3. Open the Gauge Reader program (written in Python) on the computer
4. When the foot switch is pressed, the value is sent over Wi-Fi to the Gauge Reader program, which types it into the open program and then presses Enter automatically

What we built and tested

We built the reader using 2 approaches, along with a computer-side program, firmware and manuals. The items are as follows.

• Manual for the Wi-Fi reader, which sets out the configuration steps through the reader's web page
• Gauge Reader program (Python), which receives values from the reader and types them into the open program
• USB board v3 firmware on the ATmega32U4 chip, with 3 modes
• A separate set of keyboard mode code, and the USB board circuit design

How does this prototype relate to InGauge?

This prototype falls in the same period as the 2017 InGauge USB 2.0 product documents, but it still has to be confirmed whether the v3 firmware is the same firmware as InGauge USB 2.0. The product the company currently sells and rents out is InGauge USB V2.1 from the ITAP program. The documented sequence of work is as follows.

1. 2015–2018: In-house research and development, trialling the Wi-Fi reader and the USB board running v3 firmware
2. 2017: InGauge USB 2.0 product documents
3. 2020–2021: The ITAP program redesigned the circuit, resulting in InGauge USB V2.1, which passed CE/FCC testing

InGauge USB V2.1 has a serial port mode (Mode 1) and a USB HID keyboard mode (Mode 2), the same ways of sending values that the prototype's v3 firmware has.

Confirmed results from the prototype documents

What can be confirmed is the prototype's code and manuals. The v3 firmware on the ATmega32U4 chip has 3 modes and supports up to 4 gauge channels in serial port mode. The Wi-Fi reader's manual sets out the configuration steps and how to send values with the foot switch.

The prototype documents record the code and operating steps, but not figures for the speed or accuracy of value transmission, so this page does not report such figures.

What we learned

This prototype offers 3 principles for sending values from measuring instruments to a computer.

• Send values through a channel the computer already recognises. The Wi-Fi version needs the Gauge Reader program kept open, while keyboard mode (USB HID) needs nothing extra installed. The less preparation the computer side needs, the easier it is to connect to existing software.
• Let the person measuring trigger the send when the value typed into the program must match the workpiece measured. The Wi-Fi reader and keyboard mode send values when the foot switch or a button is pressed, so the value entering the program is one the person measuring chose to send.
• Code that can send values still has to go through circuit design and standards testing as a further step before sale. The InGauge USB V2.1 currently on sale went through a circuit redesign and CE/FCC testing in the ITAP program.

How can you apply this approach to your measurement work?

If your gauge has a Digimatic port and you already record measurements in a program on a computer, you can use the same approach as this prototype: take values from the gauge's port and type them into the program as a keyboard would. For actual use, use InGauge rather than the prototype. What needs adapting depends on the receiving program and the number of gauges.

• Check that the gauge you use has a Digimatic port and a cable matching the model
• Check whether your recording program can accept typed values or must receive them through the serial port
• Agree whether the person measuring will trigger the send with a button or a foot switch, and position it to suit the workstation