Multi Drop Bus Inerface / Photon

Hi All, I need to implement an interface wit "Multi-Drop Bus / Internal Communication Protocol " with photon, this interface have the follow requirements: Baud Rate = 9600 +1%/-2% NRZ 9 BIT mode

I have many doubts: as first STM32F205 sems is supporting with USART 9BIT but Photon firmware only supporting 8BIT communication, as second there isn’t a library for this kind of communication that’s a standard to interface vending machine, and may be usefull for implementing vending systems IoT Orientend.

If someone have some suggestions, any help is appreciated.


There was a thread about alternative serial parameters on this forum, but I can’t remember where.
You might be able to find it tho’
Another thread was about half duplex on Serial1, which might also give you some clues.

@zanettistudio, though the STM32 USART does support 9-bit mode, none of the Photon firmware does. You would have to modify the USART code to provide the support. As for multi-drop, that sounds like an RS-485 bus.

One approach you could take is to use an Arduino (eg. ATmega328) do handle the serial bus communications and connect to the Photon via SPI or I2C. :grinning: