ESP32S and adapter board

All ESP32 boards running MicroPython.
Target audience: MicroPython users with an ESP32 board.
djipey
Posts: 15
Joined: Sun Dec 01, 2019 3:04 pm

ESP32S and adapter board

Post by djipey » Fri Jan 17, 2020 8:41 pm

Hi,

I'm trying to upload micropython on my ESP32 WROOM (the bare chip). I got it from here, with the adapter board:


https://www.banggood.com/ESP32-ESP-WROO ... rehouse=CN

I soldered the chip on the adapter (properly, I hope), and powered it. I didn't see any LED blinking, but I suppose this board doesn't have a status LED? (I'm used to the ESP8266).

Once powered, I tried to flash micropython on it, but I couldn't get any connection with esptool. I have sucsessfully flashed bare ESP8266 and ESP32 dev kit before. But this ESP32 WROOM is resisting...

Also, I'm a beginner in electronics and I'm not sure about one thing: the adapter board has 2 empty spots for SMD resistors (R1 and R2, you can see their spots on the pictures). At the moment I don't have any. Are they required for the adapter to work?


Cheers

OutoftheBOTS_
Posts: 732
Joined: Mon Nov 20, 2017 10:18 am

Re: ESP32S and adapter board

Post by OutoftheBOTS_ » Fri Jan 17, 2020 9:11 pm

I have used this adapter board before and there is a mistake on the board and it killed my Wroom module.

I ended up using this adaptor/programmer board and it works well and no soldering required it just plugs in https://www.aliexpress.com/item/3299111 ... 22a7c604bb

It is quite a good unit as it has the USB to serial conveter and LED indicators as well as the needed caps to maintain the power required by ESP32 and the circuits for auto boot mode

djipey
Posts: 15
Joined: Sun Dec 01, 2019 3:04 pm

Re: ESP32S and adapter board

Post by djipey » Fri Jan 17, 2020 10:39 pm

I might be interested by the adapters you mentioned if they are plug-n play, without soldering.

In the mean time, I would like to try and make my adapters work. Do I need the resistors?

OutoftheBOTS_
Posts: 732
Joined: Mon Nov 20, 2017 10:18 am

Re: ESP32S and adapter board

Post by OutoftheBOTS_ » Sat Jan 18, 2020 3:53 am

djipey wrote:
Fri Jan 17, 2020 10:39 pm
I might be interested by the adapters you mentioned if they are plug-n play, without soldering.

In the mean time, I would like to try and make my adapters work. Do I need the resistors?
Yes they r just plug and play without soldering.

The board you already have has some errors. You will need resistors and also a 100nf cap to go across the EN pin. There is 1 resistor you need to leave out as well off memeroy before I got it to work.

djipey
Posts: 15
Joined: Sun Dec 01, 2019 3:04 pm

Re: ESP32S and adapter board

Post by djipey » Sat Jan 18, 2020 9:20 am

To get the buttons working right? But I could potentially deal without them. The adapter boards I have for my ESP8266 don't have any buttons.

OutoftheBOTS_
Posts: 732
Joined: Mon Nov 20, 2017 10:18 am

Re: ESP32S and adapter board

Post by OutoftheBOTS_ » Sun Jan 19, 2020 8:41 am

The resistors are pull up resistors usually 10K.

Usually you will have to pull EN pin high via a pull up resistor so that when the reset button is pushed it will ground the EN pin and pull it low against the pull up resistor. The EN pin will need a 100nf cap as well for stability on the EN pin, any sort of dipping of the EN pin causes ghosts in the machine, there has been lots of problems with this on ESP32 dur to the WIFI causing dips in voltage.

All in all the board your using is a really bad design and there is a couple of faults (no 100nf cap on EN pin and there is also 1 of the resistors stop it from working, off memory it is the resistor on the boot pin)

djipey
Posts: 15
Joined: Sun Dec 01, 2019 3:04 pm

Re: ESP32S and adapter board

Post by djipey » Sun Jan 19, 2020 12:45 pm

Ok roger that, my adapter board is crap. I'll order the one you suggested.

That said, I'd like to understand what I did wrong. I understand the pull up resistors are there to ground the EN and GPIO0 pins when the buttons are pressed. I tried to connect these pins directly to the ground (I just used Dupont cables on the side connectoins) and I couldn't enter the flash mode. According to this page: https://github.com/espressif/esptool/wi ... -Selection, I only need the GPIO0 and EN pins to be set low to enter the flash mode right? I couldn't get there. I even tried to connect GPIO 12 to ground too, no luck.


Since I have two ESP32 and two adapter boards, I had another chance to get something to work. For the other ESP32, I only soldered the ground, 3.3V, EN, TX, RX, GPIO0 pins. Not the buttons. I wanted to connect the pins only with the side connections. I tried to enter the flash mode with EN and GPIO0 grounded, nothing. I tried to simply boot the board with EN and GPIO0 connected to VIN (with each a 10k resistor on the line), and I got no reaction from the board (I expected a new wifi network to show up). But this last result could be explained by the lack of capacitor or no firmware on the chip.

I need to roughly understand all this, because once I'm done with experimenting, I want to use the bare chip directly for my "production" projects.

OutoftheBOTS_
Posts: 732
Joined: Mon Nov 20, 2017 10:18 am

Re: ESP32S and adapter board

Post by OutoftheBOTS_ » Mon Jan 20, 2020 11:03 am

If nothing as been flashed to the blank ESP32 module then it won't do anything till you flash something to it.

To enter boot mode the boot pin (GPIO 0) needs to be held low during start up. The ESP32 will only startup when EN pin goes high. Normally you would do this with the buttons, you would hold boot the press reset while holding the boot as during the press of reset it pulls it low when pressed but when released it will go high again because of the pull up. When the EN goes high theb ESP32 will startup during start up it checks the status of Boot pin and if low then it goes in to boot mode.

Pin 12 should already be in correct state as the needed pull up restsors for pin 12 are already internal of the module.

Bare min to make the module go will be a stable power supply with 10uf and 0.1uf cap on 3.3v pin and 0.1uf on EN pin with 10K resistor pulling up EN to high so that the EN pin can be pulled low to reset. You will also need a serial to USB converter if your going to program via your PC. See the datas sheet under Peripheral Schematics https://www.espressif.com/sites/default ... eet_en.pdf

djipey
Posts: 15
Joined: Sun Dec 01, 2019 3:04 pm

Re: ESP32S and adapter board

Post by djipey » Wed Jan 22, 2020 8:22 pm

Thank you, I finally managed to boot and flash the board, thanks to your procedure. I didn't use the buttons on the adapter board, just the side connections and two 10k resistors on the breadboard.

Once flashed, I was able to access the python prompt and do some stuff, but as you mentioned, as soon as I activated the wifi interface the power dropped and the board rebooted.

Regarding the minimum setup to boot the board, I think I understood everything. The schematics don't include the switch for the EN pin though, where should I put it? Before C3 ?
Last edited by djipey on Wed Jan 22, 2020 8:32 pm, edited 1 time in total.

OutoftheBOTS_
Posts: 732
Joined: Mon Nov 20, 2017 10:18 am

Re: ESP32S and adapter board

Post by OutoftheBOTS_ » Wed Jan 22, 2020 8:31 pm

You can use the power supply from your USB to serial adapter but you will need the 10uf and 0.1uf caps on the 3.3v pin and 0.1uf cap on the EN pin. Caps help to create a stable power supply they store up power when there is plenty then discharge that power if when the power drops to maintain a constant smooth power supply. Larger caps can fill larger dips but are slower to respond, smaller caps respond super fast but can only fill a small gap so generally the power supply for any chip will have a couple of different sized caps as the small cap fill as soon as the dip starts but then runs out of power fast but by then the larger cap has started to fill in and takes up the slack.

Usually the manufacture of the chip supplies a peripheral schematic that will have on it the recommended needed supporting circuits, this is where I get these needed cap sizes from.

Post Reply