ESP32 Forum

Yes, it is eprfectlky capable of working on 3.3V (and actually will not work when fed with only 1.8V). The internal flash chip, however, is an 1.8V part. In order to generate the power supply for that, the ESP32 has an internal LDO to generate 1.8V from its 3.3V power supply. However, this power supply is configured on bootup, mainly from the state of the MTDI pin: if this pin is high, the power supply will output 1.8V, if it is low, it will pass through the 3.3V chip power supply.

All in all, your PCB will work just fine *if* you made sure that the ESP32s MTDI pin always has a high signal level on bootup.

Can someone comment if the internal flash in the ESP32-D2WD is able to handle 3.3V or what is needed to adjust to allow the ESP32 to run at 3.3V? See the picture attached.

For D2WD, power all rails except VDD_SDIO at 3.3V. For VDD_SDIO, select 1.8V voltage of the internal regulator by strapping GPIO12. Since VDD_SDIO will be at 1.8V, it must not be connected to the external 3.3V supply.

For D2WD, power all rails except VDD_SDIO at 3.3V. For VDD_SDIO, select 1.8V voltage of the internal regulator by strapping GPIO12. Since VDD_SDIO will be at 1.8V, it must not be connected to the external 3.3V supply.

Is vdd_sdio ever connected to external supply? Isn't it voltage output?

One can, for example, connect VDD_SDIO to external 3.3V supply. In this case the internal regulator will be disabled automatically. The only problem with this design is that the flash chip doesn't get automatically powered down before deep sleep, so a shutdown command needs to be sent to it (and then it still draws some sleep current from the external supply).

So I have cut the trace for VDD_SDIO and strapped the MTDI pin high. I see 1.8V on the VDD_SDIO pin which is a great start.

Now I just need to program the ESP32 with the Windows "ESP32 Download Tool, V3.4.8". Does anyone know what settings to use? My crystal is 40MHz on my PCB.
Thank you very much,
Jamie

hi

you can run a simple test on it, deselect your firmware file
and select the auto like this:
the tool check your Flash too and will select for you the right
and you see the MAC, SPI Flash Info in the dedected info window after you push start.
( without a firmware upload )





best wishes
rudi

Thank you very much for the recommendations and debug help. I found the problem. I had the wrong capacitor on the crystal so the crystal was not working. The CP2102 circuit above works great! n Again thank you!

Jamie

So I am using the ESP32-D2WD which has 16Mbits of flash internally. I can now see the MAC addresses but I am unable to program the internal flash. Can anyone see what the problem is? I have it set to QIO for the flash interface. Is that correct? Any speed recommendations for everything else? I have double checked the 3.3V power supply on an oscilloscope) and it is very good. It is solid the entire time the programmer is trying to program the flash so I know the 3.3V rail is not the problem. I have also tried different speeds for the COM port and SPI speed. I have also tried writing to different memory locations. Any help or advice would be great.
Thanks,
Jamie

So I am using the ESP32-D2WD which has 16Mbits of flash internally.

the ESP32-D2WD is the version of 16MBits eMbedded flash
and! 1.8V
for 1.8V you must use the bootstrap MTDI PIN to "high" -
have you checked VDD_SDIO for 1.8V too?
the SoC itself is 3.3V powered - this is ok, but don't forget to set bootstrap pin high for VDD_SDIO 1.8V
you can use eFuses too for this - for first settings i do proposal to use bootstrap pin.
it's the sure way


best wishes
rudi

edit: ok - see that you have do the 1.8V bootstrap in your PCB - circuit
so next step, use the auto thing i posted a post before
and let set the flash tool the things automatic.



what is the output now?