More details on the data acquisition system
Main Processor: Microchip 64Mhz PIC18F45K22
Responsible for Automation and Data Acquisition
Co-processor: Particle WiFi Module (120Mhz ARM Cortex M3 processor)
Responsible for wireless communications between the main processor and the server:
Main board
This is the Mikroe PIC7 development kit. This board itself was originally going to have a much more important role, but technology advances so fast that it's a bit outdated now. Since the work mounting it is already done, I'm just leaving it in for show.
Back when I bought the green board, I didn't have a clue how to design electronic PCB's. I'm up to speed now with a lot of practice from developing NanoEFI boards over the last two years. At this point, the only thing of importance on the green circuit board is the $1.50 microchip it houses, and the built-in USB programmer module. The real intelligence and logic in this box is going to be on a completely custom circuit board that I'm designing from the ground up just for this project (more on that in a later update).
Serial Peripheral Interface: Getting the processors talking over the SPI protocol
Getting the processors communicating with each other required a bit of hookup wire to the correct pins, and a voltage level translator in the middle. The processors communicate over a protocol called SPI. SPI is a serial data protocol that allows the chips to share information at high speed, millions of bits per second. This is more than fast enough for the streaming sensor data and commands in real time.
Although I like the "DIY" look of the hookup wire, this will all be replaced with the custom board. The new board will snap into place on the green board, and will contain circuitry for all of the voltage translation circuits, as well as all Input/Output conditioning, filtering, and protection for the overall system.
SPI Signal Diagram
Here's a good diagram of what an SPI conversation "looks like" between processors. This the main processor transmits "S" and the co-processor transmits "F". This happens about 1 million times per second at speeds that I've tested so far.
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The enclosure
Making a wall mount
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After a quick trip to the plasma table...
The unit you see on the left is the hydraulic fluid heater control circuitry and solid state relays. I'll cover details about that side of the system in a later update.
