| ??? 10/22/07 14:03 Read: times |
#146009 - a much better idea Responding to: ???'s previous message |
Please see If we can use shielded cable and Ground at one side of the circuit board.
a much better idea twisted pair where one side is ground makes (virtually) no difference, in effect, you get a "shielded wire with an imprefect shield". For direct connection uC Txd to uC RxD there are many problems except when both are in the same enclosure a) as we all know "ground is not ground" and the ground diffrence between unit a and unit b can create havoc in the transimission and - in a bad case - blow uC pins. b) your baudrate will be severely limited since you are relying on a rsistive pullup of a a signal loaded by cable capaitance. c) I, personally, refuse to let uC pins leave the board A 'cheap' method allowing a limited baudrate would be to use a buffer chip (e.g. a '126) for TxD and a schmitt (such as 2 HC14s in series for the RxD. OR - use an inverting buffer/driver and just one HC14 Erik |
| Topic | Author | Date |
| UART Maximum | 01/01/70 00:00 | |
| Baud rate ? | 01/01/70 00:00 | |
| Baud | 01/01/70 00:00 | |
| RS232? | 01/01/70 00:00 | |
| 100m on 4800 BPS | 01/01/70 00:00 | |
| How? | 01/01/70 00:00 | |
| true RS232 | 01/01/70 00:00 | |
| you do not say how | 01/01/70 00:00 | |
| a) ----- option only | 01/01/70 00:00 | |
| Twisted Pair | 01/01/70 00:00 | |
| He would not be THAT ignorant, I hope | 01/01/70 00:00 | |
| a much better idea | 01/01/70 00:00 | |
| Assumption | 01/01/70 00:00 | |
| a much better idea | 01/01/70 00:00 | |
| WRONG | 01/01/70 00:00 | |
| panacea ---> The Godess of all cure :) | 01/01/70 00:00 | |
| of course, you need to connect gnd | 01/01/70 00:00 | |
| ground problem isnt a problem | 01/01/70 00:00 | |
| Call a spade a spade... | 01/01/70 00:00 | |
| no, it is not | 01/01/70 00:00 | |
| Differential | 01/01/70 00:00 | |
| no, it is not | 01/01/70 00:00 | |
| Oh yes it is! | 01/01/70 00:00 | |
| since you control both ends ... | 01/01/70 00:00 | |
| Minimum RS422/485 | 01/01/70 00:00 | |
| mimum length for 485/422 | 01/01/70 00:00 | |
Thanks for the input to all | 01/01/70 00:00 |