AN1857 RS232 optoisolation interface

[edjiang]

Hi,

I built a Hardware connection for MC9S08MP16, which is the same as described in app note AN1857, page 13. I try to communicate using Freemaster, with correct Baud rate setting. Unfortunately, it doesn't work. When I use P&E micro debugger, the communication is fine.

I measured my PC and found both pin 4 and pin 7 is of voltage around -11V. Anyone has an idea about this configuration?

Thanks

Ed

[edjiang]

forgot to mention that I use the "real" serial com port, NOT USB port.

[michaelsteffenf]

Did you install the serial source code into your project?

Mike

[edjiang]

Hi Mike,

that is the point. I don't know anything about the serial source code and I didn't find any information from the Freemaster webpage. Previously, I use P&E micro debugger, it works fine with Freemaster, which means my project code is okay. Now I need to communicate only using com port, that is the problem I have now.

Thanks

Ed

[bigmac]

Hello Ed

For the optoisolated interface to work correctly when sending data to the PC, the signal at pin 7 (RTS) need to be set active by the PC, to achieve a voltage level of about +12 volts.  At the same time, the signal at pin 4 (DTR) should remain inactive, to retain the negative voltage level.

Regards,

Mac

[edjiang]

Hi Mac,

Thanks for the explanation. Should I do anything about this voltage setting? or it is done automatically by Freemaster?

Ed

[michaelsteffenf]

You need insert the serial driver files into the project if you’re going to communicate via serial connection. They are available on the Freescale web site in the Freemaster page.

Mike

[edjiang]

Hi Mike,

Thanks for your reply. I didn't find the files on the webpage "FreeMASTER Run-Time Debugging Tool". Could you please send me the link to the files or a screenshot of the webpage?

Thanks

Ed