ESP8266 Community Forum

- Tue Jun 23, 2015 2:58 am #21338 The UART mode is confusing for me atm so I wont go there .
If you want to flash the chip put VCC,CH_PD, and RESET high
Put GND,GPIO15 and GPIO0) Low
Don't connect any others at this point and turn the power off then on . You will get 1 flash only if the wiring is right . Then send the hex up to it Of that I am sure.

If you don't get 1 flash when it powers up you haven't got the FLASH mode which I assume is called that because you are transfering hex to the chips flash memory.

Get you modules here:

https://www.banggood.com/custlink/KvGGhGF4wG

- Tue Jun 23, 2015 4:43 am #21350 According to esptool I am correctly flashing the nodemcu firmeare. The problem is that I can't boot normally by pulling the gpio0 high. I get a 1.65V which I believe is actually the default 26MHz clock signal. I'll have to find out how to set a non-standard baud in linux to check what gets dumped to the uart at reset.

- Thu Jun 25, 2015 3:46 am #21585

According to esptool I am correctly flashing the nodemcu firmeare. The problem is that I can't boot normally by pulling the gpio0 high. I get a 1.65V which I believe is actually the default 26MHz clock signal. I'll have to find out how to set a non-standard baud in linux to check what gets dumped to the uart at reset.

I think I have the same problem. My GPIO0 is stuck at generating 26MHz clock signal. I look at the serial console, using 74880 baud rate, this is what I get:

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

- Thu Jun 25, 2015 3:26 pm #21678

GPIO2 - pull up (4k7)

I think this is wrong is should be floating or used for something else . When high on boot it pulls the chip into UART mode and thats not where you want it . See the wiki above on pin modes and connections

As I've mentioned in other the two threads where you misleaded people with wrong information about this GPIO2 issue :

I prefer trusting a spec sheet than people testimonies. the Boot process table from the link https://github.com/esp8266/esp8266-wiki ... ot-Process is proably a copy/paste from Espressif specs. It should NOT be amended to please end-users.
Been in electronic engineering for decades, the four different possible connections for an input : L, H, X and NC. BTW, X doesn't mean floating, it means "irrelevant". Not connecting a X input can still be troublesome, since EMI/RFI can disturb the input, and even destroy it if EMI/RFI is too high. We should never leaving inputs floating, except if specs says NC.

Additionnally, if the table says to put it to HIGH, even if there is currently no mode in the table that use it with LOW, it doesn't mean Espressif can decide in a future to use that for an additional mode of boot process, let's says for example thru an I2C bus. So, to respect backward compatibity, we should follow the specs to the "letter".

BTW, and I've just try it out : if GPIO2 had a X instead of H, then that would mean that we can place to LOW, but right now, in such case it does NOT boot any more ! If leaving it floating works, it is simply that, like in the old days of TTL, floating is quite the same as HIGH (except about EMI potential issue). Right now, it is confirmed : Espressif really spec it that a HIGH level is REALLY required on GPIO2 !