USB for the MC9S12DP256

I wanted to experiment with a Universal Serial Bus interface to a MC9S12.  After some research on the internet it became clear that the software side would be more difficult than hardware.  A good source of information is Craig Peacock's site: USB in a NutShell

What seemed to be the simplest answer was from FTDI. They offer royalty free drivers for Windows and other systems.  FTDI has both DLL drivers and Virtual COM Port ( VCP ) Drivers which appear to the system as an extra Com Port ( in addition to any existing hardware Com Ports ). Application software accesses the USB device in the same way as it would access a standard Windows Com Port.

FTDI has two versions of their chip; one is a USB to serial and the other is USB to parallel.  Either would have worked with the MC9S12 but I guessed that parallel interface would be faster.  I wired a Dual In Line Module to a port for data and a few bits of  another port for control. Worked great.

As a speed test I used the Tera Term terminal program and did a 32K formatted HEX dump of the MPUs memory.  Using a standard 9600 baud serial connection the dump took 2 minutes 32 seconds.  The USB interface did the dump in slightly more than one second.

DLP-USB245M in breadboard

Click on the photo to enlarge it

The photo above is of a DLP-USB245M mounted in the application area of the MC9S12DP256 Development board, DRAGON12, from WYTEC. Also visible is a DS18B20 Digital Thermometer and a DS1302 Real Time Clock.
Click here to get HC12 software for the USB245M

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This page written by Roger Schaefer. Last updated December 10, 2003