Description

Everybody knows RS-232 protocol. It’s the popular kid on the block. The All-Star. But didja know it had a bigger brother, the RS-485? It’s the one that goes to work at the steel-mill so the family can send “All-Star” to college. Yeah, it’s that kinda protocol – it gets things done, industrial-style.

Where RS-232 can only talk to one transmitter/receiver at a time, RS-485 can chate with up to 32 devices on the same data line. It also is faster (10MBit/s vs RS-232’s 1MBit/s), and can talk much, much farther (4000ft vs 50ft). The only drawback to RS-485 that it is not full-duplex communication like RS-232 – devices take turns talking back and forth down the line, much like using a walkie-talkie.

To use the capable SP3485 RS-485 transceiver, SparkFun built a board that teams it with an FT232RL USB UART IC to convert a USB stream to RS-485. The SP3485 is a half-duplex transceiver, so it can only communicate one way at a time, but it can reach transmission speeds of up to 10Mbps.

The RTS pin of the FT232RL is connected to the transmit and receive enable inputs of the SP3485, this line is used to control the transmission mode of the RS-485 transceiver. With the proper drivers installed, the FT232RL will enumerate as a virtual COM port; the drivers are available for Windows, Mac and Linux.

This breakout board includes the SP3485, FT232, TX/RX/RTS LEDs, miniB USB connector, filter capacitors, and other components shown on the schematic. We’ve broken out the RS-485 output to three different connections: (1) an RJ-45 connector, (2) a 3-pin 3.55mm screw terminal, and (3) a 3-pin 0.1″ pitch header; none of these output connectors come populated.

Features:

• Fully equipped with SP3485 RS-485 transceiver and FT232RL USB UART IC
• Operates from USB supply
• RX, TX, and RTS LED indicators
• miniB USB connector
• USB power and RX/TX lines broken out to a 0.1″ pitch header
• RS-485 input/output broken out to RJ-45 connector, 3.5mm screw terminal, and 0.1″ pitch header
• Driver/Receiver Enable connected to RTS line of FT232RL
• -7V to +12V Common-Mode Input Voltage Range

Dimensions:
Board: 1.55×0.9 inches
Get your FT232RL VCP Drivers here