Analysis: In my last blog I noted that between the display and the switches I am using about 25 pins + ground and power. So to recap here are the pins: I have added a second table which shows the I/O connections. The reason that I chose the STM32 was for its size. It can easily fit inside the enclosure (approximately 7cm square).
The Hardware: Since the original back will be of no use to me I will have to print a new one. I will have two connectors on the rear. 1) a DB-7 for my CANbus Data and 2) a DIN 5 for my 5 volts. I will have to use UTA, the University of Texas at Arlington, Maker Space Laser Cutter to cut my vector board (FR4 PCB) to shape. In this way, I can put my connect the STM32xx and the two (2) TI PCF8574 I/O expanders.
The Software Overview: The software design is rather simple as the STM32 is just being used as a dumb terminal but without the keyboard This will only need 4 keys And instead of a UART and I will be using a CANbus transceiver
|Mnemonic||J1 pins||IO Exp||STM32|
|FL - Not Used||13|
|RD.2 - Not Used||18|
|RD.1 - Not Used||19|
|A3 & A4||27||IC2-9|
|A3 & A4||29||IC2-7|
|Keep Tuned In, More To Come ~~Cris|
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