Apparently the 24VAC to DC circuit does not work correctly because the DC/DC conversion to 3.3V doesn't seem to properly work. Is the full bridge rectifier with wrong specs? https://rayshobby.net/wordpress/24vac-to-5vdc-conversion/

Ok, some clarity is beginning to form around where I went wrong... ouch.

Simulators http://lushprojects.com/circuitjs/circuitjs.html http://www.spectrum-soft.com/download/download.shtm Signal strength

RSSI - Receiver Signal Strength Indication
LQI - Link Quality Index

EDGE interrupt for HIGH and LOW (gpio.c):

#ifdef KBI1PE_KBIPE3_XPIN #ifdef KBI1PE_KBIPE3_XPIN /* XPIN_19 */ if (irqcandidate & 0x08) { if (kbimod1_reg & 0x08) { KBI1ES_KBEDG3 = !KBI1ES_KBEDG3; if (~(kbi1_val ^ kbiedg1_reg) & 0x08) if (~(kbi1_val ^ kbiedg1_reg) & 0x08) { /* Edge irq on active slope */ puts("IRQ EDGE: Active slope"); gpio_irq_handler_KBI1PE_KBIPE3_XPIN(); } else { puts("IRQ EDGE: Inactive slope"); } } else { gpio_irq_handler_KBI1PE_KBIPE3_XPIN(); /* Level irq */ } } #endif