Electronics > Projects, Designs, and Technical Stuff
DIY Modular Test Equipment Project
void_error:
--- Quote from: xani on February 08, 2018, 01:10:05 pm ---For ethernet side honestly you're probably better off just sticking raspberry pi there, it has serial, SPI and I2C on it, it's cheap, and you can then run any data acquisition directly in the system instead of pushing data to dedicated PC. Or even run a web UI with modules state/controls
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Adding ethernet is just an idea, only mentioned it because I saw it's possible with what I have so far. I'm just playing with the idea and not taking it too seriously at the moment.
--- Quote from: xani on February 08, 2018, 01:10:05 pm ---For IDing modules daisy chaining is probably easiest option, but you should also probably have modules send their name and some unique ID if a micro has it) with it. That makes it possible for code to work regardless of which order modules are put in or even (if unique IDs are used) if you reorder stuff for whatever reason. Of course, that requires a micro per board
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Found a way that requires no micro and with jellybean parts. The ST_CP pulse is already used to latch the data onto the 74HC595's outputs so it's reused by U713 to latch the input data. U715 & U712 just make the whole thing SPI compatible. U712 outputs into the SPI MISO line and the STS line acts as an active high chip select. U715 is there to delay the data by one bit. In other words, the board ID is programmed via 6 solder links. D0 & D1 will have board specific functions, like signalling an overtemperature condition.
Why I went that route is because I don't want to force anyone else building one of the aforementioned modules into using the same micro I used. Perhaps one would want to use an arduino, or STM or raspberry pi or whatever else to control the module(s).
--- Quote from: xani on February 08, 2018, 01:10:05 pm ---If you go with micro per board it would also be worth to add a single LED dedicated to identify function, that allows for making queries like "which board is ADC number 4" or "which board is one with ID 413e6f"
Or go even fancier and put RGB led on, then you can do "connect left channel to green input, and right channel to purple one"
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Going one micro per board would have been one way to make everyone happy but only if I provided a way of mounting a daughter board for each module which IMHO I found it would be a pain in the butt so I'm only doing it for the module that has the frequency counter where a micro is the only sane way to go. I should probably make a new lock diagram of how things would work together as the last ones I posted are quite outdated.
void_error:
--- Quote from: void_error on February 07, 2018, 08:27:10 pm ---I've almost finished everything needed for the waveform generator / frequency counter as far as schematics go, with the electronic load and lab power supply not far behind. Depending on how things progress I might have stuff on GitHub this weekend.
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This guy spoke too soon.
I thought I'd first see if everything fits together and it's not a huge pain in the ass to route where MCUs are employed so I had to move pin functions around. After finally getting to something doable for the UI board (yes, it strikes again) I realized it's way too big so I'm changing the connector placement from something like this to moving the 30-pin bus connector to one side and maybe the pushbuttons to the bottom below the display depending on how much I can shrink the board vertically. It currently looks like this and one can almost build a factory on top of it:
John Heath:
I like it. Do you have a picture of what it physically looks like on your bench? Have you thought of a computer interface secondary display and mouse buttons for secondary desk top computer control. This would open new doors for your modular data acquisition system . One of those doors would be the internet where I from 1000s of miles away could press a bottom to make a measurement on your bench. Can not think of a practical reason to do this but then again why does a man climb a mountain , because it is there.
void_error:
I'll be using one of these because they're cheap and I'm cheap, unfortunately (not for me) no backplane/rackmount possibility out of the box, too much work for too little gain.
Modular... hmm... nope, won't change the title but you can find something being designed to be modular here.
This is just a collection of bits of test equipment sharing a similar communications bus simply because it was easier to have it that way.
Internet? Just hook up a raspberry pi or something via UART and you can have it. Going for practical first, after fancy a bit later.
void_error:
I think I have finally managed to get the PCB sizes right for the 4 stacked boards of the waveform generator. UI ended up 115x70mm, with the waveform generator 115x95mm. It might be the time to upload some schematics to github as drafts since things might change a bit with the PCB layout which is what I'm currently working on.
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