I built my own pendant for my Rambo board using an Arduino Nano. The project had some rough edges, and I never spent the time to smooth them out, so I’ve not published it anywhere. But, when pendent projects come across the forum, I always take an interest. In your particular case, I don’t have a SKR Pro board, and other than reading other forum posts, I don’t know the specifics of getting Serial3 working.
By working, I mean are you able to successfully send commands to the SKR Pro board from your pendant? Having the Arduino powered up does not mean working.
Well now that you pointed out that the port is only 3.3v that may be the issue. It would be enough to light the LEDS but would it be enough to run it all?
There are 5V and 3.3V pins on the SKR Pro. I doubt your Arduino would power up with 3.3V. I’m guessing some of the pins on the SKR Pro are 5V tolerant, but I don’t know, and even so, I don’t know if they all are. For example, look at this block:
It is a good bet (though not certain) that the RX1 and TX1 pins are 5V tolerant.
I’ve seen a post on this forum where someone was using the WIFI connection for serial communication (not for a pendant). Looking at that block:
Given the 3.3V in the upper left corner of this block, I would be reluctant to feed 5V signals to any of the other pins on this block. As mentioned in my previous post, if I was trying to communicate to this block, I’d use a simple voltage divider to bring the voltage down, though there are specific (and inexpensive) components called level converters for this task.
If you don’t have it working (as in able to drive the control board), then the place to start is to make sure you have all the firmware and connections working correctly. I would:
- Using the Arduino IDE, open the serial monitor and use your pendent. With your board connected to your computer, verify the g-code commands are being sent after your modifications to the firmware on the Arduino board.
- Change the baud rate to 250000 and hookup your pendant to the TFT RX1 and TX1 pins and get it working. You know these pins are enabled, since your TFT uses them for serial communication. You can put your display in Marlin mode if you need a screen. In Marlin mode, the cable to the TFT pins are not used. Note that TX → RX and RX → TX between the two boards.
- Once the above two steps confirm that you have all the other potential problems solved, then go and explore Serial 3. It is possible that you’ve already burned out a pin or two…or not. You can get some verification that the pins are good by carefully hooking up a multi-meter to each pin and ground and using an M42 g-code command to set the pins high.