Need help connecting Raspberry Pi to old Com-trol MCS-4000 boards.

Hello, looking at the PDF you supplied, the communications acts via RS485 interface, with baud rate of 19200 or 38400 BPS. You can simply use an USB to RS485 interface that can be recognized by the Raspberry PI board, then use it in your program as TTYUSB0 (or similar), setting the appropriate baud, bits and parity parameters. Note that if you use an FTDI based interface, the handling of the bus direction (RS485 is always half-duplex) is done directly by the interface, so you have just to write to the serial channel or read from it, without the need for the direction control (usually involving one output line as TX enable). The FTDI chips have an automatic "1 bit before start" activation of transmission and "1 bit after stop bit" release of the bus. So, when you don't transmit any data, the receiver is enabled, and when you transmit data, the transmitter is enabled just for the requested time, freeing the bus immediatly after the data has been transmitted. Obviously, the hardware part is very simple, but you must know the protocol for sending and retrieving data. Note that the RS485 bus is multi-point, so every device connected has its own "address". I noted on the schematic that there are two rotary switches to set the address for the peripheral. However, if you don't have the protocol specs (a list of commands and the packet structure) it's almost impossible to handle it. It may be "easily" decoded if you have some controller that actually works with the device. In such case, you can use the USB to RS485 interface as a "sniffer" on the bus, capturing the packets that go from the controller to the device and vice-versa. Hope this helps...

Hello, looking at the PDF you supplied, the communications acts via RS485 interface, with baud rate of 19200 or 38400 BPS. You can simply use an USB to RS485 interface that can be recognized by the Raspberry PI board, then use it in your program as TTYUSB0 (or similar), setting the appropriate baud, bits and parity parameters. Note that if you use an FTDI based interface, the handling of the bus direction (RS485 is always half-duplex) is done directly by the interface, so you have just to write to the serial channel or read from it, without the need for the direction control (usually involving one output line as TX enable). The FTDI chips have an automatic "1 bit before start" activation of transmission and "1 bit after stop bit" release of the bus. So, when you don't transmit any data, the receiver is enabled, and when you transmit data, the transmitter is enabled just for the requested time, freeing the bus immediatly after the data has been transmitted. Obviously, the hardware part is very simple, but you must know the protocol for sending and retrieving data. Note that the RS485 bus is multi-point, so every device connected has its own "address". I noted on the schematic that there are two rotary switches to set the address for the peripheral. However, if you don't have the protocol specs (a list of commands and the packet structure) it's almost impossible to handle it. It may be "easily" decoded if you have some controller that actually works with the device. In such case, you can use the USB to RS485 interface as a "sniffer" on the bus, capturing the packets that go from the controller to the device and vice-versa. Hope this helps...

Emilio,

     I am in the process of looking for a rs485 adapter. Since I do not have documentation on the protocols I was planning to use the rs485 as a sniffer. Thank for describing how the rs485 works. Yes there is one address rotary knob on the board 0-F.

Thanks,

Teeterbuilt

Just popping up:

When your sniffing the protocol, just check the MODBUS protocol. Its widely used and plain ASCII, documents are easily found on the internet.

good luck !