I am working on a PCB with PIC18F26K22 which connects to a Redpine Wi-Fi module through UART.
I initially checked if PIC works with a simple LED blinking program with internal oscillator and it does. I check the same blinking with 11Mhz external oscillator + 27pf capacitor circuit and it works. As soon as I write code into the Wi-Fi module, my supply i.e. 3.3V and ground pins are getting shorted, burning up my microcontroller. This has happened on all the PCBs with this layout.
My observations/doubts(all suggestions/criticism welcome). My biggest suspect here is the PCB layout - 1. I initially doubted the external oscillator layout and removed the grounding below the crystal. I also placed the caps after the crystal after reading some posts on this forum. 2. Since the above didn't work , I checked Wifi working with the internal oscillator only ,but the burning persists. 3. Next I cut the Rx and 3.3V supply tracks on Wifi and hardwire them but still the problem persists.
I have attached my layout here. Any suggestions would be great!