Hardware specs

• RS485 half duplex
• Exitation: 0Vdc, 11.6 to 17Vdc regulated (not bi-polar)
• Baud: 9600
• One start, seven data, NB! ODD parity !, one stop
• Note: Manual states even parity, this has been revised

.A53 SMART CONVERTER
The A53 converts RS232 from a computer into RS485 for the bus. This converter is SMART as is changes the RS485 to transmit whenever a message is sent by the computer. No handshaking line RTS is required and no software is needed.

• Open the converter
• SW1 is on for RS485 mode
• SW2 is on for automatic handshaking
• Insert JP1 for the end of bus terminator 120 ohms
• Wire 9 to 30 volts dc to terminal 6 - and 7 +
• Turn on the power: the CTS and power leds come on
• Plug in the RJ45 cable from the RS232 connector to the computer
• Wire terminal 1 TXD+ B to the load cells D+ in parallel
• Wire terminal 2 TXD- A to the load cells D- in parallel
• To extend the RS232 cable connect white to pin 5 0v, green to pin 3 tx, blue to pin 2 rx : dsub 9 female

Set Working Address
Only connect ONE load cell to the converter at a time

• Run the slcaddr.exe program from Instrotech
• The first command line parameter is either COM0 (computer port1) or COM1 (port2)
• The second command line parameter is the working address to be set eg. UNIT1
• Once all the load cell working addresses have been set, you can connect them together on the bus

Bus test

• Run the slcraw.exe program from Instrotech to see the raw values

Terminator
If there are a lot of communication errors this can be cause by reflections at the two ends of the bus. This is corrected by putting a resistor between D+ and D- at each end.

Ref

• SBC and SCC datasheets
• SLC manual with protocol
• Revere application disk with program example files
• Instrotech example programs with pascal files