|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
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.
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|
Roger's Embedded Microcontrollers Home Page
This page written by Roger Schaefer. Last
updated December 10, 2003