Recommended Communication Protocol for parallel power system communication

Hi Aish,

Aish Ahuja said:

Is there any app note on this or similar subject?

Nope, there's no App note on this topic.

Aish Ahuja said:

Which communication Protocol do you recommend.

This depends on the developer and the intensity of the application. Previously RS-232/485 where very widely used and now a days Ethernet or MODBUS are preferred. Implementing the later would be a challenge but very much possible (search the forum for the same). As for RS232/485 would be comparatively easier. You can use the SCI peripheral for the implementation.

If I'm not wrong this parallel connection would be external right? If internal then you can explore I2C and SPI too. 

Regards,

Gautam

You can surely explore SPI in the form of data exchange bus for one cabinet system. As for external, you can go for RS-232/485 as I previously mentioned. You simply have to use a MAX-232 or MAX3221 and an RS-232 DB9 socket at both ends.
You need to check the noise interference on the data line. You might experience data corruption when your system works at higher power.
But do check and update us if you face any such issues.

Regards,
Gautam

Gautam Iyer said:

Previously RS-232/485 where very widely used and now a days Ethernet or MODBUS are preferred. Implementing the later would be a challenge but very much possible (search the forum for the same). As for RS232/485 would be comparatively easier.

Sorry Gautam but this is wrong.

1) RS-232 and RS-485 standards simply define physical (electrical) level of communication and Modbus, in contrary, is application layer protocol, thus they are on completely different OSI levels. You can implement Modbus on RS-232 or RS-485 or on TCP/IP, it's completely up to you. RS-232 or RS-485 as is don't give you anything. You will have to either implement custom protocol or use any available protocol (such as Modbus RTU, or Modbus ASCII).

2) Implementing Modbus (RTU for instance) is not harder than implementing custom protocol, if you really need a reliable communication and you are planning to send different type of data packets. In fact normally it will save you a lot of time, because standard protocols are robust and effective. Of course, if you just need to send some flags then Modbus (or similar protocol) would be an overkill.

Aish Ahuj,

You need to consider lengths. RS-232 shouldn't go for more than a couple of meters, in contrary, RS-485 with proper cable can go up to 1200m. RS-485 with Modbus is a good choice for master-slave reliabile communication especially in harsh conditions. As for SPI it's also dedicated for short distances and also is unbalanced, hence less immune to noise.

Again depends on the system design and filters used. I would suggest you to go ahead with RS-232 communication and check with its performance. The noise would affect a 3.3V communication more than RS-232 voltage level; hence you should be safe!

Regards,
Gautam