> Hi,
> I have built RS485 communication for 11 AT89S51 microcontrollers. Consist
> 1 master and 10 slave nodes. I use SN75176BP for RS485 driver. All
> microcontrollers connected using UTP Cat-5 Cables in a bus :
> Safe bias resistor-SL1-SL2-SL3-SL4-SL5-SL6-MA-SL7-SL8-SL9-SL10-resistor
> terminator.
> From SL1 to SL7 connection works fine, but from SL8 to SL10 still cannot
> connected. Total length of cables about 500m. At one end of cables i give
> termination resistor 120ohm and the other end using safe bias resistor
> Vcc-750-120-750ohm-Gnd. I'm using baudrate 9600bps for communication.
> The protocol is simple, each 100ms master will send an address. Slave
> would response if they address send by master with send a few byte of data
> to bus. These data will be read by other slave.
> What's wrong with SL8 to SL10? Can you give me a solution for these
> trouble?
> Thanks for your attention.
> Hi,
> I have built RS485 communication for 11 AT89S51 microcontrollers. Consist
> 1 master and 10 slave nodes. I use SN75176BP for RS485 driver. All
> microcontrollers connected using UTP Cat-5 Cables in a bus :
> Safe bias resistor-SL1-SL2-SL3-SL4-SL5-SL6-MA-SL7-SL8-SL9-SL10-resistor
> terminator.
> From SL1 to SL7 connection works fine, but from SL8 to SL10 still cannot
> connected. Total length of cables about 500m. At one end of cables i give
> termination resistor 120ohm and the other end using safe bias resistor
> Vcc-750-120-750ohm-Gnd. I'm using baudrate 9600bps for communication.
> The protocol is simple, each 100ms master will send an address. Slave
> would response if they address send by master with send a few byte of data
> to bus. These data will be read by other slave.
> What's wrong with SL8 to SL10? Can you give me a solution for these
> trouble?
> Thanks for your attention.
>
>
>
Do they all have the same ground reference?
regards,
DR
Reply by Frank Bemelman●August 28, 20062006-08-28
"TR6" <taufikir@telkom.net> schreef in bericht
news:-YOdnU6Ls7wfQW_ZnZ2dnUVZ_oGdnZ2d@giganews.com...
> Hi,
> I have built RS485 communication for 11 AT89S51 microcontrollers. Consist
> 1 master and 10 slave nodes. I use SN75176BP for RS485 driver. All
> microcontrollers connected using UTP Cat-5 Cables in a bus :
> Safe bias resistor-SL1-SL2-SL3-SL4-SL5-SL6-MA-SL7-SL8-SL9-SL10-resistor
> terminator.
> From SL1 to SL7 connection works fine, but from SL8 to SL10 still cannot
> connected. Total length of cables about 500m. At one end of cables i give
> termination resistor 120ohm and the other end using safe bias resistor
> Vcc-750-120-750ohm-Gnd. I'm using baudrate 9600bps for communication.
> The protocol is simple, each 100ms master will send an address. Slave
> would response if they address send by master with send a few byte of data
> to bus. These data will be read by other slave.
> What's wrong with SL8 to SL10? Can you give me a solution for these
> trouble?
First thing to do is hook up an oscilloscope and see what the
signal looks like, at the receiver end. Measure the amplitude.
--
Thanks, Frank.
(remove 'q' and '.invalid' when replying by email)
Reply by Meindert Sprang●August 28, 20062006-08-28
"TR6" <taufikir@telkom.net> wrote in message
news:-YOdnU6Ls7wfQW_ZnZ2dnUVZ_oGdnZ2d@giganews.com...
> Hi,
> I have built RS485 communication for 11 AT89S51 microcontrollers. Consist
> 1 master and 10 slave nodes. I use SN75176BP for RS485 driver. All
> microcontrollers connected using UTP Cat-5 Cables in a bus :
> Safe bias resistor-SL1-SL2-SL3-SL4-SL5-SL6-MA-SL7-SL8-SL9-SL10-resistor
> terminator.
> From SL1 to SL7 connection works fine, but from SL8 to SL10 still cannot
> connected. Total length of cables about 500m. At one end of cables i give
> termination resistor 120ohm and the other end using safe bias resistor
> Vcc-750-120-750ohm-Gnd. I'm using baudrate 9600bps for communication.
Normally this should work. I've run similar networks at 96-125kbps. Have you
checked the signals with an oscilloscope?
Meindert
Reply by TR6●August 28, 20062006-08-28
Hi,
I have built RS485 communication for 11 AT89S51 microcontrollers. Consist
1 master and 10 slave nodes. I use SN75176BP for RS485 driver. All
microcontrollers connected using UTP Cat-5 Cables in a bus :
Safe bias resistor-SL1-SL2-SL3-SL4-SL5-SL6-MA-SL7-SL8-SL9-SL10-resistor
terminator.
From SL1 to SL7 connection works fine, but from SL8 to SL10 still cannot
connected. Total length of cables about 500m. At one end of cables i give
termination resistor 120ohm and the other end using safe bias resistor
Vcc-750-120-750ohm-Gnd. I'm using baudrate 9600bps for communication.
The protocol is simple, each 100ms master will send an address. Slave
would response if they address send by master with send a few byte of data
to bus. These data will be read by other slave.
What's wrong with SL8 to SL10? Can you give me a solution for these
trouble?
Thanks for your attention.