ESP8266 - Where to find pin assignment guide for uploading code?

Question

I try to upload a script which starts a webserver on the ESP8266 with a simple web GUI where the user can enter his WLAN credentials.

/*  ============================================================================================================

    Sample code to create a setup web portal using a soft access point on an ESP8266.

    For more info, please watch my video at https://youtu.be/1VW-z4ibMXI

    MrDIY.ca

============================================================================================================== */

#include <ESP8266WiFi.h>
#include <ESP8266WebServer.h>
#include <EEPROM.h>
ESP8266WebServer    server(80);

struct settings {
  char ssid[30];
  char password[30];
} user_wifi = {};

void setup() {
  
  EEPROM.begin(sizeof(struct settings) );
  EEPROM.get( 0, user_wifi );
   
  WiFi.mode(WIFI_STA);
  WiFi.begin(user_wifi.ssid, user_wifi.password);
  
  byte tries = 0;
  while (WiFi.status() != WL_CONNECTED) {
    delay(1000);
    if (tries++ > 30) {
      WiFi.mode(WIFI_AP);
      WiFi.softAP("Setup Portal", "mrdiy.ca");
      break;
    }
  }
  server.on("/",  handlePortal);
  server.begin();
}


void loop() {

  server.handleClient();
}

void handlePortal() {

  if (server.method() == HTTP_POST) {

    strncpy(user_wifi.ssid,     server.arg("ssid").c_str(),     sizeof(user_wifi.ssid) );
    strncpy(user_wifi.password, server.arg("password").c_str(), sizeof(user_wifi.password) );
    user_wifi.ssid[server.arg("ssid").length()] = user_wifi.password[server.arg("password").length()] = '\0';
    EEPROM.put(0, user_wifi);
    EEPROM.commit();

    server.send(200,   "text/html",  "<!doctype html><html lang='en'><head><meta charset='utf-8'><meta name='viewport' content='width=device-width, initial-scale=1'><title>Wifi Setup</title><style>*,::after,::before{box-sizing:border-box;}body{margin:0;font-family:'Segoe UI',Roboto,'Helvetica Neue',Arial,'Noto Sans','Liberation Sans';font-size:1rem;font-weight:400;line-height:1.5;color:#212529;background-color:#f5f5f5;}.form-control{display:block;width:100%;height:calc(1.5em + .75rem + 2px);border:1px solid #ced4da;}button{border:1px solid transparent;color:#fff;background-color:#007bff;border-color:#007bff;padding:.5rem 1rem;font-size:1.25rem;line-height:1.5;border-radius:.3rem;width:100%}.form-signin{width:100%;max-width:400px;padding:15px;margin:auto;}h1,p{text-align: center}</style> </head> <body><main class='form-signin'> <h1>Wifi Setup</h1> <br/> <p>Your settings have been saved successfully!<br />Please restart the device.</p></main></body></html>" );
  } else {

    server.send(200,   "text/html", "<!doctype html><html lang='en'><head><meta charset='utf-8'><meta name='viewport' content='width=device-width, initial-scale=1'><title>Wifi Setup</title> <style>*,::after,::before{box-sizing:border-box;}body{margin:0;font-family:'Segoe UI',Roboto,'Helvetica Neue',Arial,'Noto Sans','Liberation Sans';font-size:1rem;font-weight:400;line-height:1.5;color:#212529;background-color:#f5f5f5;}.form-control{display:block;width:100%;height:calc(1.5em + .75rem + 2px);border:1px solid #ced4da;}button{cursor: pointer;border:1px solid transparent;color:#fff;background-color:#007bff;border-color:#007bff;padding:.5rem 1rem;font-size:1.25rem;line-height:1.5;border-radius:.3rem;width:100%}.form-signin{width:100%;max-width:400px;padding:15px;margin:auto;}h1{text-align: center}</style> </head> <body><main class='form-signin'> <form action='/' method='post'> <h1 class=''>Wifi Setup</h1><br/><div class='form-floating'><label>SSID</label><input type='text' class='form-control' name='ssid'> </div><div class='form-floating'><br/><label>Password</label><input type='password' class='form-control' name='password'></div><br/><br/><button type='submit'>Save</button><p style='text-align: right'><a href='https://www.mrdiy.ca' style='color: #32C5FF'>mrdiy.ca</a></p></form></main> </body></html>" );
  }
}

I try to figure out how I need to connect the ESP8266 WLAN module with my Arduino Uno in order to be able to upload that script. I've searched the documentation, but I can't find much helpful.

The module has these pins:

3V3 | RX
RST | IO0
EN  | IO2
TX  | GND

But in the documentation there are other pins which I don't have and the pin EN is not even mentioned in the documentation.

I connected it like this (i did not used pull up resistors yet):

[ESP8266 -> Arduino Uno]

3V3 -> 3V3 (bread board)
EN  -> 3V3 (bread board)
RX  -> RX
TX  -> TX
GND -> GND

The connection works and it responds to AT commands.

But if I try to upload a script, then it fails with:

. Variables and constants in RAM (global, static), used 28236 / 80192 bytes (35%)
║   SEGMENT  BYTES    DESCRIPTION
╠══ DATA     1504     initialized variables
╠══ RODATA   1020     constants       
╚══ BSS      25712    zeroed variables
. Instruction RAM (IRAM_ATTR, ICACHE_RAM_ATTR), used 59535 / 65536 bytes (90%)
║   SEGMENT  BYTES    DESCRIPTION
╠══ ICACHE   32768    reserved space for flash instruction cache
╚══ IRAM     26767    code in IRAM    
. Code in flash (default, ICACHE_FLASH_ATTR), used 239164 / 1048576 bytes (22%)
║   SEGMENT  BYTES    DESCRIPTION
╚══ IROM     239164   code in flash   
esptool.py v3.0
Serial port COM4
Connecting........_____....._____....._____....._____....._____....._____....._____

A fatal esptool.py error occurred: Failed to connect to ESP8266: Invalid head of packet (0xF0)

How do I need to connect my module in order to upload code?

I am using this chip. I also tested another chip (i got 4) to check if mine is broken, but I get the same error.

if you are seeing AT commands then it is connected correctly ... the ESP-01 is preprogrammed with the AT firmware and I'm not certain if it's capable of accepting a program — jsotola
– jsotola, Commented Dec 31, 2023 at 19:44
try this instructables.com/HOW-TO-UPLOAD-PROGRAM-TO-ESP-01-USING-ARDUINO — jsotola
– jsotola, Commented Dec 31, 2023 at 19:47
I followed the instructions. Uploading was successfull after I set the Reset of my Arduino to GND. But now my ESP8266 does not work anymore, there is no WLAN connection and it stopped responding to AT commands. — Black
– Black, Commented Dec 31, 2023 at 20:40
The sketch replaced the AT firmware. You have an esp-01. It is not a development board but a WiFi module, so it doesn't have an USB adapter and auto reset. — Juraj
– Juraj ♦, Commented Jan 1, 2024 at 6:21
@Juraj wow ok, how do I recognize if a board is for development, I thought each one is? Im a arduino beginner, sorry. What can you even do with such a module as mine if you can't program it? — Black
– Black, Commented Jan 1, 2024 at 14:06

Matt · Accepted Answer · 2024-01-01 18:24:07Z

The module is built around esp8266ex microcontroller. In order to make it enter into the flash programming mode the following steps must be taken.

Put mcu into reset state by pulling reset line low.
Pull gpio15 low and gpio0 low while still holding reset low.
Release reset, so it will go high and mcu will restart.
While starting the mcu will check pin states (gpio15 low=use spi flash 25xx series pre-attached to gpio6-11, gpio0 low=self programming mode, gpio2 is NOT low) and will enter the waiting state in a few milliseconds.
Release gpio0 and start data transfer to h/w uart0 (attached to gpio1 and gpio3, aka tx and rx).

So you need to ensure that: gpio0 is pulled up; gpio1 and gpio3 are attached to another host's uart by crossover connection; gpio2 is not low; gpio15 is pulled low; both reset and enable are pulled high; and, of course, you have 3v3 power and ground. Also, you need two push buttons to connect reset and gpio0 to ground temporarily. Then press reset, press gpio0 button, release reset, and, finally, release gpio0. Mcu should now wait for the data to flash. Also, when using esptool you need to tell it to skip auto-reset sequence (--before no_reset), as you're doing it manually.

Considering aforementioned pullups, their presence depends on a module you're using. For esp-01s, they all should be already there (except for the two buttons). For esp-01 (without "s"), you'll need to add pull ups for gpio0 and "chip enable" pin yourself.

There's also auto-programming sequence (which is default for esptool) also sometimes referred as "nodemcu reset method" or such. The idea is that the programming software will switch dtr and rts UART extra signals on and off before data transfer. If you have a small circuit between uart chip and esp8266 mcu that is capable to translate dtr/rts signals to reset/gpio0 states to make mcu to enter self programming mode then you won't need any push buttons anymore.

Such circuit can be made of only two npn transistors and two resistors and is searched online easily. Some boards (including nodemcu, of course) may have such circuit along with usb-ttl converter, dc-dc buck converter and usb plug all on-board. But they are bigger in size and slightly more expensive than esp-01, of course.

Also, for esp-01/esp-01s specifically, you can purchase a prebuilt adapter that provides exactly those missing parts (usb plug, dc buck, two transistor auto-circuit, ttl converter chip, some pullups and female header to plug esp-01 module in). So you can flash your modules using this adapter while sparing some space in your circuit too.

(Hint: the presence of auto programming feature could be guessed from the product photo usually by spotting two sot-23 transistors close to each other).

Or you can buy all these parts and solder such adapter board yourself. This might look a bit too much for a beginner, but, on the other hand, it could make an interesting challenge too.

@Black esp8266 is a microcontroller chip and it does have this one and a bunch of others. Esp-01 is a small board that already includes a pull down resistor from gpio15 to ground. So if you failed to spot it, it's not a big deal as you are not supposed to do anything with that pin yourself. At least, for esp-01. — Matt
– Matt, Commented Jan 2, 2024 at 19:49

Stack Exchange Network

ESP8266 - Where to find pin assignment guide for uploading code?

1 Answer 1

Your Answer

Linked

Hot Network Questions

ESP8266 - Where to find pin assignment guide for uploading code?

1 Answer 1

Your Answer

Sign up or log in

Post as a guest

Linked

Related

Hot Network Questions