uC and USB implimentation

A USB - serial converter would probably be the easiest way to go by far, compared to modifying your design to support USB. I have heard from people who have sucessfully used the converters and those that haven't been able to get the to work at all, but I imagine that they generally do work.

As far as the option of getting your design to support USB: the serial port on your PC uses RS-232, which, like USB, is a communications specification for both the electrical signals and the communications protocol. The USB protocol, however, is much more complex both from a protocol standpoint and with regards to the physical implementation.

There are many books and websites available that will get you pointed in the right direction if you wish to investigate this option. One that I would recommend is

The simplest to implement, will be the FTDI chip

The FT232L), or one of the modules based on this (the DLP-USB232M). The problem is that if your PC software also expects to see a com port, you will need to have a serial port emulation to drive the USB interface. Then at the other end, the USB chip, will need code to set it up. The FTD unit, has such an emulation already written and downloadable, and a recognised 'device' identity already programmed into the modules.

The NCN2500, is _not_ a USBserial converter. USB is already a 'serial' bus, and this is just a transceiver for this bus, to convert the signals to normal logic levels, and seperate the transmit/receive data, for connection to a microcontroller that implements USB internally. You can use this with a processor that implements a USB slave interface, to make the actual connection, but then you will end up having to add the slave code to your processor (and use a processor that implements such a port). A chip like the PIC18F4455, can do this, but offers the transceiver already built in, removin the need for the external chip in this case.

Best Wishes

Try looking at the Microchip site for the USB development board. I got one for £30 from Farnell (cheaper than Microchip direct) for a similar purpose. The board has a PIC (14F552?) and includes all the code and a demo for Windows to turn on LEDs, read switches, a pot and a temp sensor. I haven't looked at it seriously yet, but it might be of interest for the long term ... hth Neil

Have a look at:

there a half a dozen possible solutions there.

Don...

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Don McKenzie
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