Blu-DRO Now Uses the TouchDRO iGaging DRO Adapter

UPDATE Sep. 7, 2020Al stopped selling Blu-DRO boxes earlier this year. As I've been getting a large number of inqueries about Blu-DRO or some other enclosure for the TouchDRO adapters, I decided to try selling a kit that includes a pre-assembled board and a 3D printed enclosure. At this point it's available for the TouchDRO Adapter for iGaging DRO Scales and can be purchased on the new TouchDRO.com website.

I get a fair number of emails asking if I sell fully assemble board, in a box, ready to go. Although I have seriously thought about offering a fully turn-key version of the iGaging DRO controller, I couldn't get the numbers to pensil out: the cost of making a custom injection molded enclosure is ridiculously high, and 3D printed enclosures take too much time and I couldn't find a way to make it scale. Meanwhile, I knew that Al at blu-DRO.com has been selling fully enclosed Arduino TouchDRO controllers. I've met Al "virtually" on TouchDRO Bata Testing Google+ community, where he had been a frequent poster, always willing to help or answer questions. Furthermore, the feedback I got from people who purchased blu-DRO units was very positive about his level of customer support, etc. After some "noodling around" I decided to email Al and see if we can find a way to work together. A few emails later we decided that I will sell the boards to Al in bulk at a bit of a discount so he can use them in his units. This seemed to be a win-win situation: Al would get more robust controllers for the blu-DRO and I can stop worrying about creating a turn-key version of TouchDRO.

DIY Digital Readout Project Update - Display Boards Are Here

Ten brand-spanking-new LED display PCBs
for the DRO project

A week or so ago I finished laying out the LED display PCB for my DRO project. I built one unit some weeks ago using a prototyping board, but when a friend asked me to built one for her husband, I decided to bite the bullet and make a proper circuit board. This is by no means necessary, but wiring three MAX7221 on a prototyping board isn't my favorite pass time. Additionally, by using surface mount parts I was able to squeeze 24 digits (three rows of eight digits) and six tactile switches into a 5.75” x 3” board, whereas the initial prototype took 7”x5” prototype board for 18 digits (6x3) and no buttons.

LED Display for DIY DRO - Introduction to MAX7219/7221

This is the first part of a tutorial on driving MAX7221/7219 display drivers with STM32VLDiscovery board. In this part we will cover the basics, i.e. how 7-segment display work, how the shift registers work and how to talk to MAX7221/7219 chip. In the next section I will post the source code for STM32 Value Line Discover board and explain the kay points. 

As I mention in the post on DRO Design Considerations, I decided to use standard 7-segment LED display for the position readout. Since the DRO is targeted at a small milling machines, 6 digits per axis is more than enough *. This means that we need to drive 18 dits total, and by far the most convenient way is provided by Maxim 7221/7219 shift registers. Many hobbyist are intimidated by these ICs, but under the hood they are very simple. Both chips use SPI protocol to receive data and can drive up to 64 LEDs, or 8 7-segment displays. MAX7219 and MAX7221 are almost identical, with one minute difference: MAX7219 is not SPI-compliant. I will elaborate on this a bit later, but for this project they are interchangeable.

Let’s Get Stated with the DRO Project

First of all, after sleeping on the design for a few nights I decided to break the project into two stages. The first stage will be to make a functional DRO with basic DRO functionality. The second stage will be the stepper control and CNC functionality. The main reason is that the DRO will be useful by itself, and I think doing a proper G-code interpreter and stepper controller will take some time. As an added benefit, this makes for a smaller initial money outlay.

More Microcontroller Options for DIY DRO

STM32VL and STM32F4 Discover Boards

In yesterday's post I compared Arduino, LPCXpresso and few other microcontroller options for my digital readout project, but I completely forgot about my two newest toys: STM32VLDiscovery and STM32F4Discovery. I got them just a few weeks ago and haven't even had a chance to play with either, but they show a lot of promise.
These are ST Micro's evaluation boards for ARM Cortex-M3 and ARM Cortex-M4F microcontrollers. Mouser sells them for $9.88 and $16.25 respectively, placing them well within the reach of most hobbyists. Both boards come with built-in ST-Link/V2 programmer/debugger, and Unlike LCPXpresso's LPCLink, ST-Link is not locked into any particular IDE. There are even some reports of people using it with GNU C compiler and debugger. Better yet, the ST-LINK/V2 can be used to program any STM32 chip by manipulating a couple of jumpers.

Microcontroller Choice for the DIY DRO

Arduino UNO, TI MSP430 Launchpad, FEZ Domino, LPCXpresso and MSP430F2132

The core of the DRO is the microcontroller, so that's where I will start. After some "back of the envelope" calculations, here are the basic requirements:

DIY Digital Readout Design Considerations

In my last post I mentions that I'm starting to work on a new DIY project - a “Digital Readout on steroids” for my Harbor Freight (Sieg X2) mini mill. I imagine it will be one of my “constantly evolving” projects, i.e. there likely won't be a “done” state, and new features will be added as I think them up. For now I pretty much made up my mind on what will be included in the initial version, but I will try to leave some space for future improvements. The first step will be to prototype the hardware and get the basic low-level functionality working, i.e. reading the scales, writing the position etc. I will make the design as modular as possible, so the parts can be reused or easily replaced if the magic smoke runs out. The unit will consist roughly of the following building blocks (I will go into more details in future posts...)

Some Ideas for the DIY DRO Project

I bought my mini mill in January of the last year, and it didn't take long to realize that 16TPI lead screws with their silly 0.0625” per revolution were, to say the least, suboptimal. In other words dialing anything that involved more than one revolutions sucked really bad.

After some spelunking on the forums I was set on getting a DRO, but my puny toy budged wouldn't bear anything more than a Shumatech DIY DRO kit with a set chinese calipers. These kits are great value for the money, and with their new DRO-550 design running OpenDRO software they are simply a "cant's meow", but at that time Shumatech didn't have any in stock. Luckily one of the GrizHFmill goup members pointed me to Grizzly T23012 12" Digital Scale with Remote Readout scales. These work the same way as digital calipers, but have a remote display with a magnetic base (and are much easier to mount).