emilio-movi wrote: ↑
Wed May 09, 2018 7:16 am
In few words, we have develooped an expansion board for interface digital inputs to Raspberry by photocoupler; there is a power supply on the expansion board providing +5V to itself and to Raspberry through GPIO pins. The board receive the +3.3V generated by Raspberry on GPIO pin 1 and 17. This voltage is required by the transistors of photocouplers.
We confirm that this configuration prevents the PI3B+ to boot: the red power LED is fixed to on, but nothing on HDMI display, etc. When we disconnect the 3.3V (GPIO pin 1 and 17) the PI3B+ boots.
It seems there are a number of posts now reporting that add-ons using the Pi 3B+ 3V3 supply causes the Pi 3B+ not to boot, disconnecting from the Pi 3B+ 3V3 allows it to do so.
Would it be possible to post a circuit diagram of the board which prevents the Pi 3B+ from booting ?
Doing so may help the Foundation or others explain, analyse or replicate what is happening.