DB_Man
Newbie level 3
rs485 network twisted pair
Hello everyone.
Just started new here cos I'm deperately looking for an answer. Have tried a lot.
Ok, my application first:
PC --> RS232 to RS485 converter --> Digital counter RS485 --> Digital counter RS485 --> Display RS485 --> End of bus.
- All wiring is twisted pair and all devices are the same brand.
- Max length between each device 20m.
- Distance from node to device max 20cm.
I programmed my application in VB 6.0.
What it does:
[*]
<ul>Send request to device 1 - wait - device 1 sends response - read buffer - use response from device 1[/list]
<ul>Send request to device 2 - wait - device 2 sends response - read buffer - use response from device 2[/list]
<ul>Send ASCII string to device 3 for update display[/list]
That happens in a loop.
My application works in a way that I can switch on and off each component individually. Device 1 only. Device 2 only. Device 1 and 2. Update of display separately.
My problem now is that it all works fine on my desk. Once I install it where it is supposed to go the following happens:
I can access device 1 and 2 as long as device 3 is DISconnected from power supply. Once I engergise device 3, d1 and d2 aren't accessible anymore but d3 I can update. ????
I created a simple counter that increases by 1 once I hit a button in my application. That new value is sent to d3 (display). Funny is that occassionaly if I push that button I get a response from d1 or d2. But totally random. Normally I get an update every second.
Already used a different power supply for d3. Nothing.
As I said. My application works perfect without the last device and that distance is only 5 metres from the previous node. Already had the bus terminated (120Ohm) and open. Nothing.
What else can I try?
As I said it works fine on my desk whereas the distances are shorter of the wiring.
Cheers
Sven
PS: Using MSComm for serial connection. Have used different delay times between sending and receiving. RTS signal is switched within program. Works.
Hello everyone.
Just started new here cos I'm deperately looking for an answer. Have tried a lot.
Ok, my application first:
PC --> RS232 to RS485 converter --> Digital counter RS485 --> Digital counter RS485 --> Display RS485 --> End of bus.
- All wiring is twisted pair and all devices are the same brand.
- Max length between each device 20m.
- Distance from node to device max 20cm.
I programmed my application in VB 6.0.
What it does:
[*]
<ul>Send request to device 1 - wait - device 1 sends response - read buffer - use response from device 1[/list]
<ul>Send request to device 2 - wait - device 2 sends response - read buffer - use response from device 2[/list]
<ul>Send ASCII string to device 3 for update display[/list]
That happens in a loop.
My application works in a way that I can switch on and off each component individually. Device 1 only. Device 2 only. Device 1 and 2. Update of display separately.
My problem now is that it all works fine on my desk. Once I install it where it is supposed to go the following happens:
I can access device 1 and 2 as long as device 3 is DISconnected from power supply. Once I engergise device 3, d1 and d2 aren't accessible anymore but d3 I can update. ????
I created a simple counter that increases by 1 once I hit a button in my application. That new value is sent to d3 (display). Funny is that occassionaly if I push that button I get a response from d1 or d2. But totally random. Normally I get an update every second.
Already used a different power supply for d3. Nothing.
As I said. My application works perfect without the last device and that distance is only 5 metres from the previous node. Already had the bus terminated (120Ohm) and open. Nothing.
What else can I try?
As I said it works fine on my desk whereas the distances are shorter of the wiring.
Cheers
Sven
PS: Using MSComm for serial connection. Have used different delay times between sending and receiving. RTS signal is switched within program. Works.