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OpenTherm Gateway HAT for Raspberry Pi

PostPosted: Thu Oct 05, 2017 2:59 pm
by dlmk

As a proof of concept I have already replaced the MAX232 with a MAX3232 and used the raspberry pi uart directly, but I also plan to hook up other rpi HATs and want to connect them all to the SPI bus with the rpi being the master and the HATs being the slaves of the SPI bus.

Therefore, I am now trying to create an OpenTherm HAT shield for the raspberry pi. But because of the fact that the rs232 uart of the rpi is already in use by the console (And I want to keep the console for headless operation :wink: ) I wanted to communicate to the OpenTherm HAT through the SPI bus. The PIC has the ability to talk to the outside world through a SPI interface but it would be necessary to alter the firmware, because some pins are used by LEDs and the transmission takes place on the RB5 (TX) and the RB2 (RX) pins of the MC. I am very comfortable with the C programming language but not very familiar with assembly, therefore, I would like to ask if the usage of the SPI interface would in general be possible without to much hassle. And if there exists a C version of the firmware (probably not because it would be bigger in size after compilation...) that I can alter to fulfill my needs.

Thanks in advance