ESP8266 Community Forum

- Tue Apr 14, 2015 5:02 pm #14521 Hi,

I'm unable to send AT commands to my brand new ESP8266-7.
I can read the bootloader message @76800bps. But it seems to me the chip never switch to normal mode:

ets Jan 8 2013,rst cause:1, boot mode:(7,7)

waiting for host

If I understand the "mode" well (?) the boot mode 7 is inconsistent with the fact I've set pull-ups to 3.3V on GPIO0 and GPIO2 and GPIO15 is on GND.

After some more investigations, it appears that despite the pull-up resistor (4.1kOhm), GPIO0 is not at 3.3V. If I put an oscilloscope on GPIO0 and see a signal @26MHz on that line (see attached picture) ?!? Is that expected ? Did I missed something ?

A0000DS.PNG

Any clue on what's going on would be of great help!
Thank you,
- Sylvain

You do not have the required permissions to view the files attached to this post.

Last edited by Sylvain Leroux on Thu Apr 16, 2015 10:31 am, edited 1 time in total.

- Wed Apr 15, 2015 7:33 am #14593 Default output option for GPIO0 on boot is function 5 which is CLK_OUT (not general GPIO function). This is exactly what you are getting (the system clock output of 26MHz).

What are you doing with GPIO15? It needs to be pull down to GND for both booting off SPI flash and enabling flashing via UART. If it's left floating or pulled high, you'll end up in SDIO boot mode.

http://d.av.id.au

- Thu Apr 16, 2015 10:14 am #14711 First, thank you for your reply,

For some reasons, I've messed up my wiring. I was absolutely certain that GPIO15 was connected to GND -- but it simply wasn't. So long for working late at night. With the proper wiring, all works as expected. As a reference, here is my now correct wiring using one 2.54 PCB adapter to boot in "Flash" mode. Pins in red are tied to VCC. Pins in blue to GND:

ESP8266-with-module.png

This PCB has pads to solder SMD resistors to pull CH_PD up to VCC, and to pull GPIO15 down to GND -- this will save two external connections if needed.

Sorry for having wasted your time,
- Sylvain

You do not have the required permissions to view the files attached to this post.

- Thu Dec 10, 2015 10:38 pm #36202 Just wanted to say thanks for this discussion. It helped me track down a cold solder joint on GPIO15.

Some of my work