💬 RS485 MCU Module

[openhardware.io]

https://www.openhardware.io/view/639/RS485-MCU-Module

[rozpruwacz]

Hi feanor-anglin,
Did You considered powering the node over the rs-485 bus ? I found this paper (http://www.ti.com/lit/ug/tidu993/tidu993.pdf) that describes how to do it. It seem quite simple and I think that it would make the wiring much simpler (no need for PSU for every node).

[feanor-anglin]

Hello rozpruwacz,
Thank you for your comment. This idea seems quite interesting for me and certainly I will look into it in the future. But for now you need to know the best way to power up this modules is by using one PSU for the whole bus. It is very important to have common GND on every module on the bus. To do this you will need 4 wires though.

[tiana]

Hello,

I wan to make fork based on your work, i have some question:

1. How many devices can be attached to one bus?
2. Is this 328p loaded with Arduino boot loader?
3. How to make OTA update if its possible please share some doc. ?

[feanor-anglin]

@tiana thank you for your interest. Reffering to your questions:

1. Technically 32 with SP485EE. Soon we will try to check out different transceiver, e.g. ST485ECDR. According to the datasheet, it allows 256 devices.
2. You mean by the manufacturer? No. To use FOTW updates you have to use Sensebender micro bootloader.
3. We are still working on this feature, we have no tutorial yet, but we plan to write one. For now, the only instruction how to do it is here:
   https://www.mysensors.org/about/fota

[kimot]

It is a very interesting board for RS485 applications (modbus etc.).
But not quite right for Mysensors serial bus. RS485 is not designed for multimaster bus.
CAN bus drivers are most preferable.

[feanor-anglin]

@kimot in theory you might be right, but in practice... it just works. The propability of collisions is extremely low and this is, as far as I know, the only problem you can worry about. After all, it was not my idea to use MySensors with RS485:
https://www.mysensors.org/build/rs485