ESP01. Get started with the Arduino or PlatformIO IDE. Which module to choose? Pinout
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The ESP01 is an ESP8266 module installed on a miniature development board that has four expansion slots (GPIO). The difference between the versions lies in the quantity of flash memory on board by the board, 512Ko (ESP01) or 1Mo (ESP01S).
Initially developed to add WiFi connectivity to the Arduino, it has become a stand-alone module for making mini connected objects. Relays, various sensors (temperature, humidity, energy consumption, etc.), OLED display, etc.
ESP-01 vs ESP-01S, which one to choose?
The ESP01 is simply an ESP8266 module installed on a miniature development board (24.8 x 14.3mm). There are only 2 pins of the ESP8266EX module that are exposed on the GPIO GPIO0 and GPIO2 as well as the pins RX et TX for programming and debugging via the serial port.
The difference between the versions lies only in the amount of flash memory, 512 KB or 1 MB.
A few years ago, you could tell by the color of the board. This is no longer the case today even if some manufacturers keep this marketing difference.
The table below summarizes the main differences between the two versions.
| ESP-01 | ESP-01S | ||
|---|---|---|---|
 |
 |
 |
|
| Flash Memory | 512 Mo | 1 Mo | |
| Color | Blue | Black | Black |
| Possible mention | AI Cloud Inside | S Series | |
| Note | The red (Power) and blue (WiFi) LEDs are placed next to the antenna engraved on the PCB | ||
Given the very small price difference (a few tens of cents) between the two models, it is preferable to opt directly for an ESP-01S module.
ESP-01 Pinout
Whatever the version, the input / output connector (GPIO) is perfectly identical. It has not changed since the first version of the ESP01 module.
Here is the pin identification for the 2 models
Put the ESP01 module in Flash Mode
Most of the ESP32 and ESP8266 development boards most of the time integrate a UART to USB converter (CH340, CP212 …). In addition to this, the ESP8266 development kit takes care of putting the module in a particular mode which allows the binary file of the program to be uploaded to the flash memory.
However, to be as compact, the ESP01 module does not include a UART to USB converter.
You must put the module in Flash Mode yourself each time you want to upload a program from the Arduino IDE or any other code editor.
It’s quite simple, you need the pin GPIO2 be connected to GND when the module is powered on.
Then you can upload the program using a module or a USB to TTL (UART) cable. It is also necessary that the power supply is sufficiently powerful to avoid any failure to transfer the program.
The following diagram uses an external power supply (2 AA batteries). This is not necessary if the USB to TTL adapter delivers enough power. Problems are often encountered with serial cables.
Setup for uploading a program from the Arduino IDE or PlatformIO to an ESP-01 using a USB to TTL adapter.
It quickly becomes tedious!
The best is to buy a programmer (Programmer in English) which embeds both a power supply and a USB to TTL adapter.
This article explains everything in detail
There are few programmers who allow you to activate Flash Mode and in the end it is not very useful because you have to disconnect / reconnect the module each time to be able to use it normally.
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