1N4148 Programmer ---|>|--- 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 ------------------ -C2I like to know if you need a diode, battery, or both, to find out if the problem is because of too low voltage, or if it is the current. Also note if you are using a laptop or another computer with special com-port. If possible, messure the voltage at TxD with respect to ground without programmer, and the short circuit current at TxD - GND, without programmer connected.