The board I made like yours, I did not finish the PC side. Just hard coded the PIC and two pots for tweaking it.
But my plan was to configure the board, write it to flash and unit was to be stand alone. PC was only to configure it. Is that you plan as well? If so I will build one.
Need to get MAX 233 and 3232 next time I order.. Normally I use two transistors.
The Windows application downloads the settings to the Pic Chip and the Pic stores them in it's Eeprom memory as there is plenty of rooms, so this lets you disconnect it from the PC and run standalone.
I am drawing up a new design now which is going to be modular. So you have the first board that has the Max233 (I am using this level converter because I had one lying around and also it does not need caps like the max232) and main Pic Chip. Then you can attach upto 8 modular boards depending on how many optical sensors and coils you wish to run.
Each Board module will have it's own Pic Chip, Opto Sensor and Fet with BIG Heatsink this time! and will be able to monitor all the Opto inputs from extra Modules you add.
With this method the Main Pic Chip will communicate with the PC and then download the configuration to each add-on module you have in line. Then each module will be independant from the main Pic Chip and also be dedicated to the job it has been programmed to do. This then free's up the main Pic Chip to do the Tacho calculations and feed them back to the PC or even an LCD.
I have started laying up the PCB but trying to source some nice PCB connectors that will do the job of linking the modules together.
Will post more when done.
Regards
Sean.