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| External Display for Agilent 34401A (or any DMM with RS232 Output Stream) |
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| timb:
Good work dude! You were persistent and it payed off! I might end up doing this instead of using an old 386 lunchbox with an ISA GPIB card, MS-DOS and Quick Basic. |
| Harvs:
I thought this was a really good idea, so I've started playing around with it to. I've just made up an adapter for my DMM using an RN42 module and MAX232. I had them laying around already on boards so it was a no brainer. So I've started writing an app. Already I can see how useful this is going to be, however, I recon the 10.1" tablet I've got is too big for the bench. So I think I'll get a 7 or 8" tablet and a swivel mount system that I can screw into the shelf so it doesn't take up bench space. Anyway, hopefully we can collaborate in some way to make this work well. If someone wants to send me some example serial captures from a 34401A (or any other meter for that matter.) I'll try to add support as I'm writing the app, then it'll be put up on google play for free. |
| timb:
I've been looking around at different combinations of displays the last few days: TFT, eInk, OLED, Memory LCD and VFD. The idea was to make a "universal lab tablet" with onboard wireless, then I'd have little pods that could have a variety of interfaces (RS-232, GPIB) or even direct measurement modules (V/I/R, Oscilloscope, etc.)! I've got the parts coming to do a GPIB interface (75160+75161) plus some sample displays (2.7" eInk, 2.7" Sharp Memory LCD, 128x64 VFD and some 1.5" color OLEDs) for the tablet portion. However, you just gave me a brilliant idea. I think I'll pick up a cheap 7" Android Tablet and start by just focusing the wireless pods. I can get super cheap (<$5) TTL serial to Bluetooth modules, so I'd put one of those in each pod and have it just connect to the tablet. Are you interested in adding support to your app for them? :D |
| Harvs:
--- Quote from: timb on November 15, 2013, 07:46:30 pm ---Are you interested in adding support to your app for them? :D --- End quote --- Yeah of course. Adding support for another device that streams is only going to be a couple of lines of code to deal with the packet format, or any bazar ascii chars the manufacturer decided to throw at it (and how you interrogate the device to get what function it's on, and range). However if a device doesn't "stream" its readings, and needs to be polled, then that's a bit more work. Bluetooth is easy and cheap. It also has the advantage that you only need the two devices to work easily. It's also been surprisingly robust on my bench. However, TCP/IP via WiFi is also an option that could be used, and it looks like you can get modules off ebay for around $15ea that have RS232 output. From the viewpoint of the Android device, it's very similar to work with. Just a slightly different setup, i.e. look for an IP address instead of a pair device. Most of the work from the app perspective is in getting the charts to display how you would naturally expect them to with all input conditions. This actually isn't trivial, and requires a lot of manual code intervention to get it all to look right. So yeah, adding more devices and/or features it the relatively easy part. At first I'll be looking at everything the 34461A can do as a starting point for features. |
| timb:
Okay, cool. Yeah, streaming wouldn't be a problem. Another option for WiFi is the CC3000 modules from TI (which cost $20 in one off quantities). They basically let you add WiFi to simple micros over SPI. The advantage is the SimpleLink Configuration software that runs on iOS/Android/PC and Mac, which makes getting the device on the network super trivial. Anyway, I'll be starting with Bluetooth since that's super easy to implement. A feature I did want to have would be the ability to upload an "Instrument Configuration File" to the pod, which would (in the case of GPIB) contain information on the command sets the device(s) support or (in the case of RS232) the protocol of the device. This way the pod could send data back to your app in a device agnostic manner. (I.e., the microcontroller inside my pods will translate between a standard data format and whatever the instrument uses.) Perhaps use something like SCPI for the output format. A nice advantage to having the pods be able to directly control the devices is you could use them as standalone data loggers as well. |
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