A huge company based in Florida (USA) asked us to solve its problem: it needed to drive several Industrial systems that are located about 100 meters apart. Furthermore it needed to acquire information from each remote unit, manipulate the received data and activate further interfaces according to the data itself. Depending on the data, it also had to close the contact of a local relay.
His question was: do we use a PC board with RS485 interface (the interface onboard of the remote units) and then do only the software or do we design a custom card with an RS485 interface and its embedded firmware? After about a week of reflections we arrived at the solution that objectively seemed to us the best and cheapest.
We used a Microchip Pic18 microcontroller with a double serial interface on a very economical two-sided PCB. Assembly is always SMT except for terminal block connectors and pin headers.
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