I'm using RP3B. I'm using piscope, as I don't have an oscilloscope available.
- After I boot my RP3B with nothing attached to the GPIO port, if I start pigpiod and piscope, I see all my GPIO with a constant signal level, as expected.
- After I boot my RP3B with a ribbon cable (IDE 40 pins) attached, and connected to a empty protoboard, if I start pigpiod and piscope, I can see some activity in GPIOs 4 & 14 (TXD). They look like clock/data running continously. It is not the same signal in both GPIOs. Unfortunately I don't have a print screen (and I'm cautious of connecting that cable again). But I can come with one if it looks safe.
- If I turn off the RPB3, detach the cable, and boot again, GPIOs return to normality (that is, no activity after boot).
Does anyone known what is happening? Thanks.
pi@raspberry:~ $ cat /proc/device-tree/model Raspberry Pi 3 Model B Rev 1.2 pi@raspberry:~ $ uname -a Linux raspberry 4.14.52-v7+ #1123 SMP Wed Jun 27 17:35:49 BST 2018 armv7l GNU/Linux pi@raspberry:~ $ pigpiod -V 64
piscope version: 0.4