justDIY
Active Member
I've got a board which uses nearly all the pins on my pic. The way the layout came together, PGC and PGD needed to be used as inputs.
They are connected to a push/pull output of a touch sensing chip. I'm not sure what the output stage looks like on the touch sensor, but even with both Vss and Vdd disconnected, the touch sensor still loads PGC and PGD too much for the programmer to program.
The touch sensor has an active-high output, so the pins are held low until a 'switch' is activated and then they go high.
The outputs can source and sink up to 20ma but Quantum recommends drawing as little as 1ma of current from the outputs to improve the response time and accuracy of the chip.
If I use a 4.7k resistor between the connector for the "buttons" and the pic pins, it will limit current to just over 1ma. That should help reduce the load on the programmer, right? I'm not using the Vpp pin for anything accept mclr and vpp, it is pulled high through a diode and resistor.
Any other suggestions? I don't have a lot of room left in the layout, or I'd just cheat and use something like a hex inverter to buffer the inputs.
They are connected to a push/pull output of a touch sensing chip. I'm not sure what the output stage looks like on the touch sensor, but even with both Vss and Vdd disconnected, the touch sensor still loads PGC and PGD too much for the programmer to program.
The touch sensor has an active-high output, so the pins are held low until a 'switch' is activated and then they go high.
The outputs can source and sink up to 20ma but Quantum recommends drawing as little as 1ma of current from the outputs to improve the response time and accuracy of the chip.
If I use a 4.7k resistor between the connector for the "buttons" and the pic pins, it will limit current to just over 1ma. That should help reduce the load on the programmer, right? I'm not using the Vpp pin for anything accept mclr and vpp, it is pulled high through a diode and resistor.
Any other suggestions? I don't have a lot of room left in the layout, or I'd just cheat and use something like a hex inverter to buffer the inputs.