ROB LUND

RS232 via SPI on DEMO9S08QG8

Discussion created by ROB LUND on Apr 4, 2007
Latest reply on May 21, 2007 by ROB LUND
Back in October 2005, Freescale had their rollout tour of the S08. I attended a seminar and got a Demo board. During one of the labs, they gave us a sample Codewarrior project which exercised the hardware SPI port, using the RS232 link to a PC. With a terminal app on the PC, you could work with the various features of the board, like PWM, the A/D, etc. Very nifty.

I finally got around to playing with this Codewarrior app for its SPI guts. I observed something strange. If I attempt to run this program from the board alone, I get nothing but garbage out the RS232 port, almost as if the parameters were slightly off (baud rate, parity, something). In the source code, it appears to come up natively in 4800 baud.

But when I run the app from the CW debugger, I get recognizable output on my terminal (using the excellent RealTerm, btw). Apparently, this is the only way to control the comm settings. I still don’t understand why it can’t be run from the board alone.

I’m guessing it’s because the crystal on the board (P/N FS12.00) isn’t a nice denomination of 4800. And apparently the debugger locks that in precisely? Is this correct?

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