Android DRO Mini FAQ #2

As the interest in the Android DRO project grows, so does the number of questions I get each day. Some of those questions keep coming up regularly, and since it’s been almost a year since I posted the “Android Digital Readout Micro FAQ”, it’s time to post another one. This post will not cover every question you might have, but hopefully it will address most of the common ones.

Mixed Scale Controller Firmware Posted

Recently I've been working on a new version of a DRO controller that will be able to read a combination of different scales. Although the project is taking much more time than I anticipated, I’m making steady [but slow] progress. Last week I had some free time, so I was finally able to button-up some stability issues with the common “Chinese” scales. Unfortunately I still haven’t finished a truly universal version, so you won’t be able to mix glass and capacitive linear scales (yet). Never the less I posted two versions of the firmware: one that read up to four scales and one that reads the common capacitive linear scales. Links to both versions are posted on the DRO Project Downloads Page.

Finishing the Voltage Shifter for Mixed Scale DRO

A few weeks ago I posted the build instructions for an adapter board that can be used for interfacing various digital scales to the MSP430 Launchpad DRO controller. Following those instructions you will end up with a base adapter board that still needs to be configured for your particular setup. This includes providing each scale with an appropriate power supply voltage, hooking them up to the corresponding “virtual ground”, and connecting the adapter to the MSP430 Launchpad. In this post I will use the DRO unit I built for my own mill as an example of a mixed-scale setup.

Build Instructions for Voltage Shifter Circuit

Last post covered the design considerations for the Voltage Shifter required for the Mixed Scale DRO Controller. As promised, in this post I will provide detailed build instructions for this circuit. The board is designed to work with up to four scales and has three power rails. One provide 3.3V power supply to the comparators and [potentially] iGaging scales; the other two can be set to any voltage between 1V and about 18V. Although the firmware doesn’t [yet] support glass scales or tachometer input, this board is ready for them.

3"x4" 1200 hole stripboard
with a track cutting tool

Voltage Shifter Circuit for Mixed Scale DRO Controller

In the last post I introduced the new version of DRO controller that is able to read a mix of common digital scales. You might recall that “Mixed Scale” controller uses the same MSP430 Launchpad development kit as the “Basic” version, but requires a bit of extra hardware. Unlike the the iGaging scales, which work quite comfortably with the 3.3 Volt power supply, most other inexpensive capacitive scales use 1.5V (nominal) power supply. This means that their outputs can’t be reliably read by the MSP430 microcontroller. Similarly, glass scales and quadrature encoders use 5V power supply. MSP430’s inputs can tolerate up to 3.6V, so connecting the glass scales directly to the Launchpad will permanently damage the inputs.

Mixed Scale DRO Controller Project Update

Mixed Scale DRO Controller with MSP430 Launchap

So far the DRO controllers I’ve designed have been able to read only the IGaging (Shahe) Remote DRO scales. Lately I’ve been getting an increasing number of requests for a firmware that could read the standard “chinese” linear scales.A few months ago I started working on a new version that would do just that. Although the project is still a bit rough around the edges, I’m pretty sure that the hardware will stay unchanged and any future updates will be done via firmware. Rather than holding off until the whole shebang is done, I decided to post the stable version of the firmware. In the next few posts I will provide details for the project, design considerations, build instructions and firmware implementation.

How To Upload Firmware to MSP430 Launchpad

A few months ago I posted build instructions for a DRO controller that uses MSP430G2553 microcontroller with a TI MSP430 Value Line Launchpad. Compared to the original version that used Arduino, the Launchpad version has a few advantages, such as lower cost and simpler construction. On the other hand, firmware upload process is not as user-friendly as that offered by the Arduino software. Fortunately, you don't need to install the full-blown IDE, list TI Code Composer Studio or even the MSPGCC tool chain. Instead the pre-compiled firmware can be flashed using a free command line MSP430 Flasher tool offered by Texas Instruments.

Android DRO Application Settings

This post refers to the old version of the application. Please refer to TouchDRO Settings Overview for the updated information.

As I mentioned in the last post, the new version of the Android DRO application has a lot of updates. In addition to the new functions there is a plethora of internal changes. Some of the new features are accessible through the “Settings” screen. The good news is that if you intend to use the application with one of the iGaging controllers, the default settings will be sufficient to make it usable out of the box. On the other hand, to take advantage of the new features, you will need to get your hands dirty. In this post I will try to explain what each of the settings does, hopefully making the setup pain-free.

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.