A Box of C.H.I.P. SBC (and a DIP, too)

When I last showed what was going on with my new CHIP SBC it was rather crude. Well, since then I’ve put it into a plastic enclosure, along with a power switch, voltage regulator, a USB hub, and a 32GB flash memory plug-in. I’m still using the VGA board with this iteration. For the next time around I will use the HDMI board, since the mini-monitor I found will accept either. Here is what it looks like:

20170129_144252

The monitor is something I found on eBay, and for about $25 more than what I paid for the one without a case. Oh well, live and learn. It is a 10.1″ diagonal screen with a 1280 x 800 display. I found mine on eBay, but I’ve recently seen where Walmart (!) is selling these for about $105, which is more than what I paid for mine but still not too bad.

Yes, the enclosure is rather plain, but its main job is to keep everything in one place, as you’ll see a little later on below. The keyboard is a wireless Rii RT-MWK01, with a built-in touch pad. It uses its own 2.4GHz dongle (included in a compartment in the keyboard). Other than it being very, very small (less than 6 inches wide), it seems to work acceptably. It will also fit perfectly on the front panel of the enclosure, as shown below:

20170129_150422

I can, of course, still use a Bluetooth keyboard, or connect a mouse and keyboard via the USB ports. One thing I’ve noticed with the Rii keyboard is that it will go into a dormant mode after about 5 or 10 minutes (I haven’t timed it, to be honest). When that happens the yellow connection light in the upper left-hand corner of the keyboard will go out. Pressing the shift key will wake it up and re-establish the connection, so not a big deal. It’s charged by plugging in a USB cable with a mini type connector on the ‘B’ end.

Inside the enclosure, shown below, there is the CHIP with the VGA board, mounted with the VGA board against the bottom of the enclosure. Next to it on the right is a voltage converter, which in this case is taking the 12-18V DC input from the barrel connector on the back panel and regulating it down to 5 V. The JST-PH connector seen in the image on the back of the PCB is soldered to the GND and CHG-IN pins on the U13 connector, and then tacked down with a small dollop of epoxy. For some reason I could not get the battery switch-over circuit on the board to work correctly (even with a real LiPo battery), so rather than spend a lot of time diagnosing it, I decided to bypass that and just give it 5V directly and let the on-board regulator do its job. The power switch is wired before the converter, not after it.

20170129_160546

On the other side there is a compact 4-port USB 2.0 hub with two extender cables connected. These are brought out as type A USB connectors on the rear panel. One of the hub ports is used by a 32GB flash module, and one is used by the keyboard’s dongle (not shown here–it was still plugged into one of the rear USB connectors when this photo was taken). I used a short right-angle USB cable to connect the hub to the CHIP. The hub is mounted on a piece of perf-board because the mounting points in the enclosure interfered with the hub. So I glued the hub to the perf-board with RTV and attached the perf-board to the enclosure with nylon stand-offs and self-tapping screws.

Now that the front panel is taken up by the Rii keyboard I only have the available space on the rear panel if I want to add anything. I can also extend the I/O capabilities with additional hubs, as described in this earlier post. So now I have something I can use to do test automation, run a robot, control a greenhouse, or use as a fancy calculator with data-logging capabilities (watch out, MakerPlot!). It would be trivial to give this little box the ability to talk with industrial Modbus devices using an inexpensive USB-to-RS485 bridge, like this one.

And, now that I think of it, I should probably toss in a second DC converter and dial it down to 5V to provide power for the hub. That way I won’t have to worry about the 100 mA per-port current limitation.

There is a lot I can do with just the USB interface, but if I want to move beyond USB and connect things directly, then I have something of a dilemma. The VGA and HDMI boards both take up all the connector header pins. Unfortunately there doesn’t seem to be a lot of activity in the CHIP community for creating and selling ready-made add-on boards (i.e. Dips). The NT CHIP blog does list some homebrew add-on boards, but none of them are what I’m looking for. You can see them here and here. What I need is something that will bring out the I/O pins without precluding the use of the VGA or HDMI interface boards, or replace the VGA or HDMI with a different board that doesn’t hog up all the I/O connections. I’m not interested in looking at the CHIP’s GUI on an old vacuum tube type monitor or a TV set using the composite video output.

Nonetheless, with Bluetooth and USB I can still do a lot with Arduino boards without the need to connect directly to the CHIP’s PCB. I think I’m going to order three or four more CHIPs and VGA boards. The more I play with it the more possibilities I keep thinking of for it. A touch screen monitor (with a USB interface for the touchscreen–works like a mouse) would also be rather cool.

If you are interested in some build instructions and a sourced BOM for this project, let me know in the comments and I’ll toss it up when I build the HDMI version in a month or two.

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Little Buddy

An awesome little friend

Jordi the Sheltie passed away in 2008 at the ripe old age of 14. He was the most awesome dog I've ever known.


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