| ??? 09/13/06 12:41 Read: times |
#124187 - not pantyhose Responding to: ???'s previous message |
In many RS485 implementations, the \RE (Receiver enable, active low) is grounded and the DE (Driver Enable) pin is controlled by the microcontroller, in other implementations both the pins are controlled by the microcontroller, which is a better method?
This is not pantyhose, one size does not fit all I would say that you only need /RE permanently grounded if you have a possibility of collisions. E.G. J1708, which is a bastardized 485, works on collision detection and thus the receiver is permanently enabled. Said in another way: If you have ONE master and a proper protocol, tie the two together, if any doubt, leave /RE grounded and check what comes back when transmitting. Having /RE grounded and throwing away recieved bytes when transmitting makes zero sense. The only value of a grounded /RE is if you verify the transmission by comparing the received with the transmitted. as always anyone attempting RS-485 without reading "ten ways to bulletproof RS485" first is making trouble for himself it can be found under 'best serial appnotes' in <--- links Erik |
| Topic | Author | Date |
| RS485 and DE, \RE | 01/01/70 00:00 | |
| not pantyhose | 01/01/70 00:00 | |
| Thanks Erik | 01/01/70 00:00 | |
| stick to the National and B&B stuff | 01/01/70 00:00 | |
| the worse 485 wiring | 01/01/70 00:00 | |
| automatic termination is the solution | 01/01/70 00:00 | |
| what\'s that? | 01/01/70 00:00 | |
| its simple | 01/01/70 00:00 | |
| Cool! | 01/01/70 00:00 | |
| hmmm | 01/01/70 00:00 | |
| actually very simple | 01/01/70 00:00 | |
| I am still none the wiser | 01/01/70 00:00 | |
| chain | 01/01/70 00:00 | |
| I've got it. | 01/01/70 00:00 | |
| It works, you work out the details | 01/01/70 00:00 | |
| maybe not biasing A&B... | 01/01/70 00:00 | |
| then use a high enough voltage | 01/01/70 00:00 | |
| biassing | 01/01/70 00:00 | |
answers | 01/01/70 00:00 | |
| if you supply via cable... | 01/01/70 00:00 | |
| Transceiver with switchable termination | 01/01/70 00:00 | |
| thanks for the tip! | 01/01/70 00:00 | |
| great.Oliver, just this | 01/01/70 00:00 | |
| it would, but think this through | 01/01/70 00:00 |