RS-485 packet length

[jkjoy]

Hi all,

In my project Im using a master and 4 slaves(no. may increase). Master polls all the slaves and all slaves replies its status. Baud rate is 19600.
I have two queries:
1)How long should master wait for a slave to respond, to raise a communication fault (2 byte data transfer)? What I mean to know is the packet length.
2)Does the master/slave need to transmit the same data again to ensure good communication? If so how many times?

Thanks

[janko.kaljevic]

Hello,

Master calculates CRC for message that will be sent. This is checked on Slave side, and thus user knows if the transmit was successful.
Please check Help file for received message format.

Best regards.

[jkjoy]

Thanks for your reply.

I checked help file. But how many bytes are used for CRC?

Im repeating my previous 2nd query. If the master sends a frame, how can i ensure that the slave will receive it? Shall I send the same frame again and again till I get a reply from the slave, Or only once?

Thanks

[jkjoy]

Hello,

Master calculates CRC for message that will be sent. This is checked on Slave side, and thus user knows if the transmit was successful.
Please check Help file for received message format.

Best regards.

Thanks for the reply.

My 2nd question was, do I need to transmit the frame again to ensure proper reception? Or how can I make sure the receiver receives the data?

[janko.kaljevic]

Hello,

In Help file we have explained how CRC is calculated. Also there is no need to send each message twice.
Just check if the CRC is OK and then request for new data or repeat sending.
This part really depends on your project requirements and you should make this choice.

Best regards.