How to make programmer working:

a) Too low voltage swing at RS232 output.
b) Too low current at RS232 output.
c) Other software, or hardware problems. (Use P50XV15.ZIP).
d) Too low voltage to program e.g. PIC12C508

a) Diode in RS232 ground makes it possible to use the voltage swing more efficient:


                2x1N4148                                Or one resistor:
                |-|>|-|                                 (300 to 400 ohm)
   Programmer --|     |-- RS232 GND (7)         Programmer --[ R ]-- RS232 GND (7)
                |-|<|-|

However, laptops with only +/-5V voltage swing will not work properly.

b) Try to add a 2*9V battery with serial connected current limmiting resistor across C2:

   +18V ------[E220]------ +C2

    0V  ------------------ -C2

d) The reson for the too low voltage, may bee that the programmer short RTS to GND by D4 and PIC too. That means that some computers, that not have surfient power to keep the signals high, will drop voltage on TxD, and then not have enough voltage to program PIC12C508. Also the high value into PIC, may lead some current into ground, and thereby take some power from Vdd, too. The solution here, may bee a resistor in serie with RTS (maybee 1K) or the solution by Hyvatti or the solution by mee for PP3.