uSD_nCS inhibits use of D4 as INPUT_PULLUP

[berossm]

The uSD_nCS line passes to ground through RN6 & RN8. As a result this overcomes the internal pull-up for D4.

For my application I needed all of inputs as pull-up. To work around this I removed RN8 as I did not need uSD access.

My recommendation to improve this is to add another pair of pads with a trace between them like the I2C isolate that allows isolation of the D4 line between RN6D and the microcontoller.

[jonoxer]

Thanks for the suggestion. D4 is joined to RN6 using the track shown in the screenshot, passing along the bottom layer. There's a small space in the region shown by the red highlight, so the track could be cut at that location.

The EtherTen is due for a big update anyway, to replace the old W5100 which is now becoming hard to get. I also want to change the USB socket to USB-C, and make a few other changes. I'll leave this bug open as a reminder for me to add a cut-track solder jumper in D4 for the next revision.