DIY DRO Adapter for Shahe Scales

TouchDRO adapter for Shahe scales supports Shahe 5403-xxxA scales, also known as the "Digital Linear Scales with Remote Square Display" which use Mini-USB cables. By using a fast adaptive refresh rate, this DRO scale interface adapter effectively minimizes the perceived refresh lag and maximizes position readout stability.


This is an upgraded version of the TouchDRO adapter for Shahe 5403-series and Machine-DRO M-Sure MS-278 DRO scales. It uses a more powerful 32-bit processor and more advanced software. It supports up to four scale inputs, tachometer input, and touch probe/tool setter input.

DIY DRO Adapter for Shahe Scales
DRO Adapter for Shahe Scales uses Mini-USB Connectors

The adapter is sold as a ready-to-use board with pre-installed Mini-USB Female connectors [USB Mini-B ]. It is built in an ISO-9001 factory using high-quality name-brand components and is inspected to meet stringent IPC-A-610 Class II standard. Each unit is carefully re-inspected, programmed and fully tested before shipping to ensure excellent performance and long-term reliability.


  • Four scale inputs via Mini-USB cables
  • Tachometer input with a wide RPM range
  • Touch probe/tool setter input (TouchDRO app support coming in the next version)
  • Digital signal post-processing and jump detection*
  • Powerful multi-core 32-bit processor
  • Bluetooth connectivity for a clutter-free installation
  • Ready for Lithium battery for scale power backup (battery not included)

* The firmware uses a combination of signal over-sampling and outlier detection to detect and ignore momentary jumps and reduce the flickering of the last readout digit.

Supported Scales

This DRO adapter supports the following scales without the need for additional soldering:

  • Shahe 5403-xxxA and 5403-xxxF Remote Display Scales
  • Machine-DRO M-Sure MS-278 Scales

If your scale's display looks like one of the displays shown below, the scale will work with this TouchDRO adapter.

Scales supported by TouchDRO Adapter for Shahe Scales
Scales supported by TouchDRO Adapter for Shahe Scales

Other Supported Scales

In addition to the scales listed above, the adapter can work with the following scales and encoders:

Scale pinouts are described on the relevant scale details pages linked above.

Package Contents

TouchDRO Adapter for Shahe scales is a fully assembled, programmed and tested, sold either as a standalone board or as a kit with a 3D-printed plastic enclosure. To complete your DRO setup you will need to provide a set of compatible scales and a 5V Micro-USB power supply (common phone chargers work great in this application).

Adapter with 3D Printed Enclosure

DIY DRO Adapter for Shahe Scales with 3D Printed Box
DRO Adapter for Shahe Scales with Box Package Contents
  • TouchDRO adapter for Shahe Scales
  • 3D printed adapter enclosure with acrylic insert
  • Stainless steel metric hardware (4 pcs. M3x20 screw; 4pcs. M3 nut)

Standalone Adapter Board

  • TouchDRO adapter for Shahe Scales



Scale Inputs 4
Tachometer Input Yes
Probe/Height Setter Yes
Battery Backup Yes (battery not included)
Power Supply 5V DC, Micro-USB
Current Draw Approx. 250 mA
Width 2.5"/63.5mm
Length 1.9"/48.3mm

Recommended Operation Conditions

  Min Typical Max
Tachometer Pulses/Second 0.5 1,000 10,000
Tachometer Accuracy +/-1%
Position refresh rate 1Hz (idle) 8Hz (capacitive scales)
16Hz (glass/magnetic scales)
RPM refresh rate 1Hz 1Hz
Probe/Limit switch trigger time 1us 20us (capacitive scales)
1us (glass/magnetic scales)
100us (capacitive scales)

Absolute Maximum Ratings

  Min Typical Max
Supply Voltage* 3.3V 5.0V 5.5V
Current Draw 20mA 120mA 300mA
Scale Signal "High" Level 2V 3.0V 5.0V
Scale Signal "Low" Level 0V 0.8V 1.0V
Probe/Tach/Home signal "High" Level 2.0V 3.0V 3.3V
Probe/Tach signal "Low" Level 0V 0.8V 1.1V
Other inputs (Prog., JTAG, SPI) 0V 3.3V 3.3V

Mechanical Drawings

Fig 1: Mechanical Dimensions


Useful Resources

3D Printed Enclosure Assembly

Place the board into the enclosure with components facing up and power input aligned with the corresponding opening. The fit should be pretty close, so it is best to start at an angle and push the protruding part of the USB power sockets into the opening in the enclosure as shown in the picture. Then, lower the board into its position and gently press on it until it makes solid contact with the enclosure.

DIY DRO Adapter for Shahe scales placed into the enclosure
DIY DRO Adapter for Shahe scales placed into the enclosure

Insert the clear acrylic insert into the recess as shown in the photo below and place the lid on top of it. Ensure that the PCB mounting holes are aligned with the openings in the enclosure before inserting and tightening the four screws.

DIY DRO Adapter for Shahe Scales Acrylic Insert
Acrylic insert is placed into the recess before the lid is closed.

Port Functions

Fig 2: Input Ports
Port Description 5V Tolerant Note
X,Y,Z,W Inputs Inputs for four linear axes Yes Pulled up to 3.3V
Tach Tachometer input Yes Pulled up to 3.3V
Probe (unbuffered) Tool height setter/touch probe input Yes Pulled up to 3.3V
PVR Micro-USB Power supply input, 5V DC nominal N/A
PVR 5V Power input N/A Micro-USB input jack
5V 5V Power input/output N/A Connected in parallel with PWR
BAT 1C LiPo battery connection N/A Optional, used to provide power backup to the scales

Scale Inputs

This DRO adapter board comes with pre-installed USB Mini-B female connectors. Next to each connector, there is a set of holes for a 5-pin 0.1" header that breaks out Vcc, Ground, Clock and Data lines for the axis (pin functions are marked on the underside of the board).


Tachometer input is pulled up to 3V and works push-pull or open drain sensors that output 3.3V square wave.

Touch Probe

Inexpensive touch probes and tool height setters work similar to a simple electrical switch. Depending on the configuration, when the probe touches the workpiece, it either opens the circuit or closes it (normally-closed or normally-open, respectively). TouchDRO board supports (and automatically detects) both types.

The probe can be connected as follows: connect one side of the switch to Ground and the other to the probe pin. If the probe has a LED, it has to be reverse-biased (backwards), or the input won't work. To test this, connect the probe to Vcc and Ground. If the LED lights up (either when the probe is touching or not touching), reverse the leads.

Power Supply

This DRO adapter is designed to be powered by a common Micro-USB power supply such as phone charger. Alternatively, +5V and Ground pins are broken out next to the Micro-USB connector to allow the use of a panel-mounted power supply jack instead.


The optional 1-cell Lithium battery can be used to provide backup power in case the adapter's power supply is disconnected. It is designed to work with Lithium Polymer batteries that have built in over-discharge protection circuits and use 2-pin JST-PH (2.0mm pitch) connectors. The charging circuit is pre-set for 100mAh charge rate and can be used with any battery that is larger than 100 mAh. In practice, the battery capacity is constrained by the physical space available in the 3D printed enclosure, which is roughly 7mm x 30mm x 45mm.

Recommended batteries:

Fig 3: LiPo battery in TouchDRO enclosure

Note: LiPo battery naming convention is based on their physical size. For example, a LP-503562 battery measures 5mm x 35mm x 62mm. Likewise, LP-803260 measures 8mm x 32mm x 60mm.

Status LEDs

DRO scale adapter has three LEDs:


Green LED is lit when the main processor is receiving power.


Blue LED indicates the current status. The codes are as follows:

Fig 4: Status LED Status Patterns


Red LED indicates the status of the battery charge monitor. When the battery is not connected, the state of the LED is irrelevant. Otherwise, the red LED is lit when the battery is charging and off when the battery is charged.

Connecting the Scales

  • Shahe 5403-series and Machine-DRO M-Sure MS-278 scales that come with Mini-USB cables can be plugged directly into the pre-installed USB Mini-B connectors
  • Shahe 5401-series scales require a 5-conductor Mini-USB cable to be connected directly into the input header pins
  • iGaging Absolute DRO Plus can be connected using a set of USB Mini-B breakout boards
  • Glass/Magnetic Scales and other 5V quadrature encoders can be connected directly to the board following these instructions

IMPORTANT: Always disconnect the power supply and the battery when plugging or unplugging scales to avoid ESD damage to the scales or the adapter.


Proper grounding is vital for reliable function of capacitive DRO scales. Unreliable ground connection or ground loops can lead to such issues as drifting position or random resets. In order to avoid ground loops, there should be a single reliable connection to the machine chassis. Ideally, scale frames should be isolated from the machine. If the cables are shielded, the shields should be tied to the ground only on one side and as close to the central grounding point as possible.

The board provides a number of easily accessible grounding points. Each port has a dedicated ground pin that is tied to the common ground pour. There are two ground pins next to each Mini-USB port and finally, the mounting holes are tied to the common ground as well.