DIY DRO Adapter Kit

DIY DRO Adapter Kit (Unassembled) is based on the second generation 32-bit TouchDRO hardware. It supports up to four scale inputs, tachometer input, and touch probe/tool setter input. The kit includes a bare printed circuit board, a microcontroller pre-programmed with 32-bit TouchDRO Universal firmware, and all of the components needed for building a TouchDRO adapter.


The DIY Digital Readout Adapter Kit is designed from the ground up to be cost-effective, easy to build and offers excellent performance and reliability. The kit comes pre-programmed with the second generation universal TouchDRO firmware and supports most modern 5V Glass and Magnetic DRO scales and many 3.3V capacitive scales. Each input line can be individually configured to provide 5V or 3.3V supply voltage.

DIY DRO Scale Adapter Kit
Finished DIY DRO Scale Adapter Kit

The circuit uses a dedicated Schmitt trigger to provide fast 5 Volt-tolerant input for standard Glass and Magnetic scales and the necessary noise protection for the capacitive scales. In conjunction with the optimized 32-bit firmware, it can handle 1 micron DRO scales moving at 100 mm per second (100KHz edge rate). At the same time it can extract maximum performance from the iGaging/Shahe Capacitive DRO scales by applying digital filtering and glitch rejection.

Kit Contents

This kit comes with high-quality name brand components that are derated to provide ample headroom for long-term reliability and durability.

DRO Adapter Only

DIY DRO Scale Adapter Kit contents
Contents of DRO Adapter Kit
  • Printed circuit board (HASL finish), electrically tested and inspected to meet IPC-A-600 Class II standard
  • ESP32 DevkitC module
  • Set of Texas Instruments ICs (74xx14)
  • HIgh-quality Panasonic electrolytic capacitors
  • Name brand resistors and capacitors

DRO Adapter With DB9 Connectors

DIY DRO Scale Adapter with DB9 Connectors Kit contents
Contents of DRO Adapter Kit with DB9 Connectors

In addition to the above, this options includes:

  • D-Sub 9 connectors
  • Pin headers
  • Jumper wires for connecting various scale configurations

To complete the build, you will need to provide a set of compatible scales, a suitable non-metallic enclosure and a 5V 500mAh Micro-USB power adapter (an old phone charger works great for this purpose).

Each circuit board is fully electrically tested by the manufacturer. Additionally, I personally program and test every microcontroller, inspect each PCB, and check the kit before shipping it out.



  • Supports four linear axis inputs, tachometer, and a touch probe or tool setter input
  • Scale inputs are 5V tollerant and can be individually configure for 5V or 3.3V scales
  • Per-scale bypass capacitors filter out transient spikes on the power supply lines
Scale Inputs 4
Tachometer Input Yes
Probe/Height Setter Yes
Power Supply 5V DC
Current Draw Approx. 300 mA
Width 87 mm (approx 3.4")
Length 78 mm (approx 3.1")

Supported Scales

This TouchDRO adapter supports a wide array of Glass and Magnetic DRO scales, many standard rotary encoders that output a quadrature signal with a 5V level, iGaging EZ-View DRO scales, iGaging Absolute DRO scales, and Shahe Remote DRO Linear Scales.

To ensure that your particular scales are supported, please refer to their documentation. For glass/magnetic scales, ensure that the scales use positive 5V power supply voltage and output quadrature signal with a 5V level.

For more information about supported quadrature scales, refer to the pages linked below:

For capacitive scales, if your displays looks like one of the displays below (including color and markings), this adapter will work with them. This includes:

Scales supported by TouchDRO DIY DRO Adapter
Scales supported by TouchDRO DIY DRO Adapter

If you are unsure which scales you have, please refer to the list of Compatible Capacitive DRO Scales to identify your model.

Mechanical Drawings

Fig 1: Mechanical Dimensions

Circuit Schematic

Fig 2: Circuit Schematic

Bill Of Materials

This DIY DRO kit includes all of the components needed to assemble a TouchDRO adapter.

Value Description Qty. Reference
PCB TouchDRO Adapter PCB, Tin/Led Plated, Green solder mask, White silkscreen 1 N/A
ESP32 Devkit V1 ESP32 WROOM Dev. Kit 1 U1
74xx14 SN74HC14N Hex Schmitt Trigger 2 IC1, IC2
Capacitor, 100 uF Cap. electrolytic, 100uF, 35V 2 C14, C15
Capacitor, 0.1uF Cap. ceramic, 0.1uF 50V 8 C1, C3, C5, C7, C9, C10, C11, C12
Resistor, 4.7 KOhm Metal film resistor, 4.7 KOhm, 1/4W, 5% 10 R1-10
Resistor 47KOhm Metal film resistor, 47 KOhm, 1/4W, 5% 10 R21-R30
Pin Header Pin Header, 4x1, 1" spacing 4 X,Y,Z,W
DB9 Connector DSUB-9 Femal, 9 Pins 4 X,Y,Z,W
Jumper Wires Dupond Jumper Wire, 100mm 8 X,Y,Z,W


Useful Resources

Port Functions

Port Description 5V-Tolerant Note
X,Y,Z,W Inputs for four linear axes Yes Pulled up to scale Vcc
Tach. Tachometer input Yes Pulled up to 5V
Probe Touch probe input Yes Pulled up to 5V
Power 5V Power input N/A USB Micro-B

Axis Inputs

TouchDRO DIY DRO Adapter Kit supports up to four axis inputs. During the assembly, the inputs can be individually configured to work provide 3.3V or 5V power supply to each axis. Data lines for the input will be pulled up to the selected Vcc voltage.


The board supports non-directional tachometer input. The tachometer input pin is pulled up to 5V ; the tachometer should provide a sinking (NPN/open-collector) or push/pull output.

Touch Probe

Touch probe input is a binary on/off input. The pin is pulled up to 5V. The firmware can handle either a normally-open or normally-closed probe. During boot time, it detects the state of the input and assumes that the probe is in the "Off" state; the opposite state will be treated as "On".

Power Input

The board is powered by a standard 5V regualted power supply, such as a phone charger, etc. For best results, a power supply should provide at least 500 mA of current.


Proper grounding is very important for the stable operation of your DIY DRO setup. In order to reduce EMF issues, ground the board to the machine's frame and ensure that the scales' cables are connected to the ground only on one side. Mounting holes on the board are tied to the ground fill, as are all of the ground pins. For more details please refer to the "Avoiding Common DRO Scale Problems" page.