I design a cape for BBB.
this cape use a lot of of bbb gpio (28 as input - opto isolated, 24 as output - relay).
I launch some bonescript to work with.
all works when I plug the cape after bbb has started.
but if I plug the cape before the bbb start, it does not boot : only the power led swith on. other leds keep off. the bbb won’t start.
I think it is a problem with the bonescript GPIO device tree not loaded at boot time.
can someone confirm that ?
do I need an eeprom on my cape to configure device tree on start up ?
or I will have a chance to do that only programmatically ?
If you load the boot pins with your cape, you will affect the boot options read by the processor on power up, and your board will not boot. This has been discussed many times on this forum, and it is mentioned in the System reference Manual. It wolf be a good idea to read the manual and understand what those pins on the expansion headers do, before you use them.
Read BBB-SRM paragraph: 6.7 and 8.3
I drive some pins needed for the boot process