RS 485 Interface

We have three boards as follows

1)

First board has CPU connected with CAN BUS and 24 bit delta sigma ADC in SPI mode and one 24C02 (i2c) interface and ADC data is sent either to second calibration board or third board any one at one time. There are totally 50 number of such board

2)

Second board is only calibration board and function is board is only one time or periodic check of above fifty boards and it has six nos of seven segment digital display and 4 nos keys

3)

Third board is receiving data from 50 nos boards one by one at speed 5 boards per second

This data is sent on RS485 modbus for PLC communication

This data is also sent by GSM 4G network on cloud



Please suggest suitable micro controller and application note