FMS PIC interface problem - Notebook serial port will not power PIC

[jkoesterpe]

Some time ago I built a PIC (12C508) serial interface that after testing on my notebook computer, I thought didn't work. I tried it recently on my desktop computer and it worked fine. Unfortunately, my desktop computer does not have the processor speed to run FMS. I see that others have had this problem apparently due to low power on the notebook serial interface. Is there a modification I can make to add power (from the radio or a seperate power supply) to the PIC? I'd rather not start over, but if I have to, I'll go with USB.

[phildc]

I designed my PIC (to PC serial COM) cable to take the power from the transmitter, not from the PC.
Control signals are not designed to provide power, and you avoid all problems of correct settings, powering the port on portables, aso.




and it works for 98,ME,2K,XP.
Only possible limitation, the PPM signal from the transmitter must be within TTL specs: low < 0.8V, high > 2.4V.

[Cuban Flyer]

Hi

You coud try using a 3.3v zener rather than the 5.1/5.6v usually used in the designs, The pic will run at the lower volage.


cubanflyer

[phildc]

Quickly checked the specs. Seems to work at 4MHz.
'Hi' would be 25% of voltage + 0.8V.
If someone does the test, please append.

Thanks for the remark,
Philippe.

[jkoesterpe]

[Eric Brouwer]

[phildc]

Good summary, Eric.
I designed my PIC serial cable with minimum number of components, NO transistor(s) and NO Max232. It will only fit the transmitters that have a connector including the power, and a suitable PPM signal level, but as already said, it works on all current Windows versions and on most PC models, portable or not.

So, the ones who still have problems, feel free to try the cable (and take advantage of associated RC utility softwares)!



Philippe.