ESP32 Forum

If i have a resistor (tested with 1k and 10k) between GPIO12 and VCC and click EN button, I get this:

>ets Jun 8 2016 00:22:57
rst:0x10 (RTCWDT_RTC_RESET),boot:0x33 (SPI_FAST_FLASH_BOOT)
flash read err, 1000
Falling back to built-in command interpreter.
OK

Before click EN button, GPIO12 was defined as SCLK for SPI1

What is this built-in command interpreter, and any idea what happens ?

Update, just found, its a very Basic Rom Console (?)

Gpio12 is a strapping pin to set flash voltage. When pulled high voltage is 1.8 which your flash chip doesnt work. You can force setting in efuse.

If we look at the ESP32 data sheet, we find that a set of pins are defined as strapping pins. What this means is that the signals present on these pins at boot time affects the operation of the device. Think of these as operational flags that are read only at boot time. The pins are:

GPIO0
GPIO2
GPIO05
GPIO12 - MTDI
GPIO15 - MTDO

GPIO12 (MTDI) - seems to control the voltage used for SDIO. The default is low.

What this means is that if GPIO12 is high at boot time, you will be affecting the operation of the device. From your description, that seems to prevent the ability to access the module flash memory. Since the ESP32 then can't reach flash memory, what is it to do? The answer is that it runs a basic interpreter that is built into ROM that, I'm guessing, will be of little value to you. I suspect the command interpreter might give you "enough" function to do some very basic debugging.

Also, in case this is an issue in production, it's actually possible to program an efuse to force the ESP32 to use a certain flash voltage and ignore GPIO12.

Behold the BASIC interpreter: http://hackaday.com/2016/10/27/basic-in ... 2-silicon/
Someone needs to get GORILLA.BAS running on this.