RS485 Tranceiver IC's RX Pin - E1.20 RDM (Remote Device Management) Protocol Forums

ericthegeek · March 25th, 2015

To add to what Scott said, it's a good idea to look at the actual 485 signals, and not just the digital side of the 485 driver. The analog waveforms on the bus may help you determine if you have multiple line drivers that are trying to transmit at the same time.

Also, microcontroller delay routines are notoriously inaccurate, especially if there is an RTOS involved. A 100us delay will be *at least* 100us, but can often be much longer depending on how it's implemented. Use the scope like Scott suggested to see the actual timing.

(I'm about to sign off for the night, so we'll talk again tomorrow)

StephenYim · March 25th, 2015

Dear sblair & ericthegeek,

Thanks for your help. I changed a new RS485 Tranceiver, and the RDM-100 discovered my RDM-Slave finally. Thanks!

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March 25th, 2015	#1
ericthegeek Task Group Member Join Date: Aug 2008 Posts: 390	To add to what Scott said, it's a good idea to look at the actual 485 signals, and not just the digital side of the 485 driver. The analog waveforms on the bus may help you determine if you have multiple line drivers that are trying to transmit at the same time. Also, microcontroller delay routines are notoriously inaccurate, especially if there is an RTOS involved. A 100us delay will be at least 100us, but can often be much longer depending on how it's implemented. Use the scope like Scott suggested to see the actual timing. (I'm about to sign off for the night, so we'll talk again tomorrow)

March 25th, 2015	#2
StephenYim Junior Member Join Date: Mar 2015 Posts: 11	Dear sblair & ericthegeek, Thanks for your help. I changed a new RS485 Tranceiver, and the RDM-100 discovered my RDM-Slave finally. Thanks!