Hi Experts,
I am posting this on behalf of the customer. Here it is below.
We have currently developed a product for one of our clients' requirements where we required RS485 communication for up to 256 Nodes, for which we are using SN65HVD3082 IC.
We are using Nuvoton M0516LDN Controller for Master and Nuvoton MS51FB9AE Controller for slaves.
Currently, we have succeeded in communicating up to 100 slaves with their masters. but the time taken for communication to finish from 1 to 100 goes around 6 to 7 seconds which is quite far from our expectations. we are expecting the communication to get completed from 1 to 256 within maximum of 2 seconds. baud rate that we are using is 9600. 19200 and greater baud rate does not work.
Communication Pattern
- Master sends one Byte of data to slave 1 (DATA = "1")
- Slave 1 Acknowledges it and sends one byte of data back to the master (NO DELAY IS PROVIDED) (DATA = "K")
- NO DELAY IS PROVIDED
- Master sends one byte of data to slave 2 (DATA = "2")
- Slave 2 Acknowledges it and sends one byte of data back to the master (NO DELAY IS PROVIDED) (DATA = "K")
- and so on upto 256 slaves
Inside a loop of 256, the master sends one byte of data to each slave one by one. and the same is acknowledged by each slave. If the acknowledgment is not received by the master, the Master registers the same as COMMUNICATION FAULT.
As mentioned, we have succeeded in Communicating 100 Slaves to date, but takes a lot of time. but when we add a 120 Ohms resistor at the end of line, we are not able to communicate even with a single slave. Currently, the distance between each slave and master is not more than 24 to 30 Inchs.
I am attaching a circuit diagram we are using for RS485 Communication. Request you to please suggest any changes required to meet our requirements.
Immediate response will be highly appreciated.
Best regards,
Jonathan