This appears to be an interaction with an existing usage of Pin 0 itself, although it's unclear to me from the Lora32 pinout exactly which function I overloaded.

I moved the Serial RX to GPIO pin 23 instead, and now all works fine.

I'm using a Heltec WiFi Lora32 module, with a NEO-6M GPS module attached to serial 2, albeit with RX configured to use GPIO Pin 0 instead of Pin 16 since the Lora32 uses Pin 16 as its OLED Reset pin. I've found that I can't establish communication with the GPS unless the IDE's USB serial monitor is ...

Thanks - that was it. I'd found the flash speed setting for 26 MHz, but not the main crystal setting!

Has anyone got the Heltec WiFi Lora 32 board working with ESP-IDF? Mine appears to successfully flash, but when I run "make monitor" I get output like this: ets Jun 8 2016 00:22:57 rst:0x1 (POWERON_RESET),boot:0x17 (SPI_FAST_FLASH_BOOT) configsip: 0, SPIWP:0xee clk_drv:0x00,q_drv:0x00,d_drv:0x00,cs0...