ESP8266 Community Forum

- Thu Aug 04, 2016 4:40 pm #52147 I did my pre-development work with an ESP-12.

I designed a board that included a WROOM-02 which I just fired up for the first time.

It's behavior is nothing like the ESP12 and I'm hoping someone can explain what I have found.

The board design has an ARM micro as the master and the WROOM-02 as the slave. The Master controls the WROOM-02's Rest, Enable, and Program pins.

The following is the first 200 msecs after Enable goes HI and Reset goes HI (I keep the WROOM-02 in a reset condition to minimize current draw until it's capabilities are required).



The Enable goes HI before Reset goes HI.

The two other signals are the TX0 output (top) and the GPIO0 - PGM pin.

The following is an exploded look at the activity on the GPIO0-PGM pin



My guess is that it appears to be a SPI clock but the WROOM-02 documentation does not define any activity on this line.

I attempted to receive the TX0 data. Tried the two standard baud rates .. 9600 and 115200. Neither of those were good.

I did a timing analysis in the bits and determined the baud is 74960 .. or close to that.

I told the logic probe that the Async Serial baud was 74960 and the data appears correct.



Two questions:

#1 What is the 25 mhz activity on the GPIO0 pin?

#2 What is the baud rate out of reset .. is this baud standard for out-of-the-box activity.

NOTE - this WROOM-02 is a fresh purchase from Espressif with no attempt to flash new code.

Thanks for any insights/comments.

Joe

- Thu Aug 04, 2016 5:09 pm #52149 It behaves exactly the same as ESP12, of course they are both using the same chip ESP8266.
At Reset, the internal bootloader is executed, the GPIO0 is in function 4, which is CLK_OUT (26 Mhz), and the initial baudrate is effectively 74880.
It is up to the firmware to re-initialize the GPIO and the UART baudrate.

- Thu Aug 04, 2016 7:41 pm #52158 Thanks.

I was unaware of the clock-out.