Input on PD1?

I’m short of IO lines on my Orangutan and need to use PORTD.1 as an input. However, the 1K R2 resistor and LED on PD1 load down the input device (an encoder), so I just get “0” plus a dimly lit red LED.

Therefore, I need to remove either R2 or the LED, and I would rather remove the resistor. I’ve stared at the board for a bit but the interesting traces, such as the one to pin 31 on the uP (PD1), “go underground”. Can anyone point me to R2 on the board (mega168 version) or suggest an alternative (e.g. trace cut)? A photo would help!

Thanks, Jim

Hello, Jim,

I’ve attached a drawing of the layout below. It’s viewed from the bottom side, with bottom layer in blue. The trace for PD1 is highlighted, and the white arrow points to a spot on the bottom side where you can either cut the trace or remove the resistor. Please let me know if something isn’t clear.

- Jan

Thanks, Jan

You are up late! The diagram is exactly what I need, and I’ll cut the trace.

While we are at this, can you suggest the best way to disable the pot on ADC7? I need that input too, although I think I already located the trace to cut. The only outputs on my project are the motors, display and beeper.

It is a great idea to have the built-in pot and LED for testing/demo purposes, but all should probably have a jumper for easy removal from the circuit. I notice that you’ve done this for some of the I/O devices on the later boards. By the way, the LV-168 is very interesting!

Best, Jim

Another drawing is attached, with ADC7 highlighted and a white arrow showing a proposed trace cutting spot.

- Jan

hello, Jan

I want to set the port D1 to be input port, too, but cannot view the image ‘layout_pd1.gif’ you mentioned, would you reload the picture. I use the SV-328, is it correct to desolder the red led for using the PD1 port as input port, I want all 8 ports to read the QTR-8a.

Thanks, Prasert

Those pictures should be working again. They are not relevant to the SV-328, though. On the SV-328, it should be very easy to see the trace going to the resistor and LED; you can either cut the trace or desolder one of the two parts.

- Jan

Thanks; just severed the trace between the resistor and red LED on my 328, and pin D1 is now responding properly. :slight_smile: