New Version of Android DRO Coming Soon

When I released last version of the Touch DRO application early this year my plan was to have a new version out by April. This, obviously, hasn’t happened due to a number of reasons, including a busy work schedule, a never ending list of things to do around the house etc. On top of that, from the received feedback, I realized that I had to make the “guts” of the DRO application much more robust before the new features can be added. Now, after a fairly major overhaul, the application is getting ready for the release and includes some of the lacking functions.

This version of the DRO is optimized to be used on a milling machines with three or four linear scales but with a few minor tweaks can be adapted to a lathe. Some functions, such as tool offset, will work identically on a lathe DRO.

Three Ways to Improve iGaging DRO Scales Reliability

Shielded USB cables can eliminate most of the noise issues
and costs only a few Dollars

In the last post I covered the root causes of the two most common reliability issues with iGaging digital scales. Although those scales catch a good amount of flack of being unstable when mounted on a machine, the problems are rarely caused by the capacitive transducers. In my experience the problems with random resets and unstable readings can be traced to the wiring and are relatively easy to remedy. The mods described below can be done for under $10 total in less than an hour but can make a huge difference.

Reliability Issues with iGaging Digital Scales

Many people are wary of digital readout setups that use capacitive scales because such setups tend to be sensitive to electrical interferences. A shop full of motors, fluorescent lights, transformers and other equipment is a noisy environment and when that noise gets into the DRO system it can cause havoc with the readout. The most common symptoms of such issues include random resets and floating position readout. While it appears that all “chinese” scales and calipers are somewhat prone to these issues, the majority of the complaints fall on IGaging Remote Digital Readout scales. Surprisingly the scales themselves are rarely the culprit. In my experience 9 out of 10 problems with the iGaging scales can be traced to the wiring and/or the power supply.

AccuRemote vs. iGaging DigiMag Digital Scale Comparison

12" iGaging AccuRemote next to DigiMag scales

Recently iGaging has introduced a new Stainless Steel model of their “Remote Readout” digital scales. The new “AccuRemote Digital Readout” scales are supposedly much more accurate and robust than the older DigiMag model, making them a good candidate for a hobby DRO setup. I’ve been getting emails from people wondering if these scales are compatible with the TouchDRO application (or more accurately, TouchDRO Bluetooth Controller), but since I don’t yet own a set, I wasn’t able to confirm this. When a fellow machinistweb.com forum member CaveBob graciously offered to lend his set for a few days, I jumped at the opportunity. Since Bob gave me permission to take one of the scale apart I think it will be helpful to do a side-by-side comparison to see if the scales are really that much better.

Arduino DRO DIY Build Instructions

If you’re planning to build a basic digital readout using iGaging “Remote DRO” scales and the “Touch DRO” Android application, you will need to make a controller that will interface the scales to the tablet. At this point I’ve designed two different version: one is based on Texas Instruments MSP430 LaunchPad and the other uses an Arduino. Both controllers offer the same functionality so the choice comes down to a personal preference and the availability of the microcontroller board. Yesterday I posted build instructions for the Launchpad version. In this post I will provide detailed step-by-step directions for a DRO controller using Arduino UNO and an inexpensive Bluetooth adapter.

Build Instructions for MSP430 Launchpad Digital Readout Controller

UPDATE April 17, 2021 - updated build instructions can be fond in the DIY DRO Build Guide on the new TouchDRO.com website.

I’ve been receiving an increasing number of requests to post some build instructions for the digital readout controllers. While working on the step-by-step guide (and building a unit in process) I got sidetracked and ended up designing a controller that can read multiple scales. Even though that project still requires some work I decided to update the basic version of the readout controller to be pin-compatible with the new version.

In this post I will concentrate on the MSP430 Launchpad DRO controller that can read up to four iGaging scales using the middle-of-the-road build described in the Parts List for MSP430 Digital Readout post.

Harbor Freight Caliper Data Format

Last week I started putting together the new firmware that will allow the MSP430 Launchpad version of the digital readout to read a mix of different scales and calipers. My last post discussed the needed hardware changes and touched on the high-level requirements. With the adapter board build and tested I was able to start investigating the data formats used by the small collection of calipers I was able to put together. Using my trusty Open Logic Sniffer I was able to identify two different protocols. BG Micro Digital Indicator used the 48 bit protocol described in the excellent article "Chinese Scales" by Shumatech. Surprising none of the other calipers used this protocol.

Mixed Linear Scale DRO with MSP430 Launchpad

An increasing number of readers have been asking me to add support for other encoders to my Digital Readout application, especially the “standard” Chinese scales and cheap calipers. Although I’ve been experimenting with the idea for some time but never got around to getting it done. Last weekend, while working on step-by-step build instructions for the MSP430 Launchpad DRO controller, I realized that I was much closer to the solution than I previously realized. The MSP430G2553 microcontroller that ships with the newer version of the Launchpad kit is a very capable chip that should be able to read three or four different scales with no problems. After digging through my and my father’s garages, and a trip to Harbor Freight I was able to round up six different-looking calipers and a BG Micro “Digital Indicator”, so I was ready to start experimenting.

Troubleshooting Common DRO Connection Problems

Lately I’ve been getting a fair number of emails and comments from people having various problems connecting the Android application to the Arduino Digital Readout controller. Almost all of them fell into one of three following “buckets”:

• The controller does not appear in the “Select a Device” dialog
• The application is unable to connect to the controller
• The application appears to connect but connection is lost almost immediately

The good news is that those problems are usually easy to resolve, so in this post I will try to address the most common scenarios. The solutions are designed for Arduino UNO board connected via a Linvor HC-0x transceiver (AKA Bluetooth-to-serial adapter) but should work for other combinations as well.