Hi, I have built RS485 communication for 11 AT89S51 microcontrollers. Consis
1 master and 10 slave nodes. I use SN75176BP for RS485 driver. Al microcontrollers connected using UTP Cat-5 Cables in a bus : Safe bias resistor-SL1-SL2-SL3-SL4-SL5-SL6-MA-SL7-SL8-SL9-SL10-resisto terminator. From SL1 to SL7 connection works fine, but from SL8 to SL10 still canno connected. Total length of cables about 500m. At one end of cables i giv termination resistor 120ohm and the other end using safe bias resisto Vcc-750-120-750ohm-Gnd. I'm using baudrate 9600bps for communication. The protocol is simple, each 100ms master will send an address. Slav would response if they address send by master with send a few byte of dat to bus. These data will be read by other slave. What's wrong with SL8 to SL10? Can you give me a solution for thes trouble? Thanks for your attention.