Monday, March 12, 2007

NIM100 Getting to the RS232 ... (Hack Part 2)

In the previous post we discovered where the RS232 is accessible inside the NIM100.

Now we need a RS232 cable to get to it. Since the signal is not in standard RS232 12V but TTL logic, we will need a converter. The easist way to build one is to use a Radio Shack (Future Dial) "Mobile Phone Data Cables" .

Almost any of the FutureDial cables which have a small box in the middle like the one above contains a Prolific PL2303 chipset (DataSheet) which converts USB to RS232 TTL. These cables are usually used to connect to CellPhones.

Open the Small box in the middle of the cable and check the Pinout of the PL2303 against the board accessible pads. You will only need TX, RX and GND. (The image below shows a sample mapping)

WARNING: not all cables are the same so check the DataSheet to make sure you map the right signals from the chip.

Make a connection between the pads on the cable to the NIM100 RS232 pads and you are done. If you want you can do this cleanly by adding wires and jumpers to the Datacable and headers on the NIM100 Board. (That makes life easier to plug/unplug the RS232)

Now is time to install the driver for the USB to RS232 Cable.

Find the driver here for Windows, you will not need a driver for Linux.

Under Windows the driver will recognize the cable as a COM(x) which can be accessed with Hyperterminal (use 115200 8N1 Hyperterminal setting).

Under Linux start minicom and set the port to /dev/ttyUSB0 115200 8N1.

Happy hacking, and please post a comment if you decide to do something with this !!!

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