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.
Ask RS485 Trouble ?
Started by ●August 28, 2006
Reply by ●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 ●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 ●August 28, 20062006-08-28
TR6 wrote:> 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 ●August 28, 20062006-08-28
TR6 wrote:> 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.If address selection 1s done by software, can slaves 8 to 10 receive when placed in the 1 to 3 hardware positions? Section isolate into hardware/software. Don... -- Don McKenzie E-Mail Contact Page: http://www.dontronics.com/e-mail.html Micro,TTL,USB to 1.5" color LCD http://www.dontronics.com/micro-lcd.html USB,RS232 or TTL to VGA Monitor http://www.dontronics.com/micro-vga.html World's smallest USB 2 TTL Conv http://www.dontronics.com/micro-usb.html
