ESP8266 serial bridge WIFI to UART

 ESP-01 -> USB-TTL

===================

3v3, EN -> 3V
TX      -> RX
RX -> TX
GND,IO0 -> GND

IO0 -> GND -- programming mode
IO0 -> 3.3V -- normal boot mode

RST - via button - GND - when you press button it resets

It draws around 60-80ma @ 3.3V. Can check the USB to TTL 3.3V regulator on the back for max power. Mine is AMS1117. Can supplu 1A - (1.5A maximum)

sudo apt install esptool

Read chip info:
esptool.py --port /dev/ttyUSB0 flash_id
esptool.py --port flash_id

Output:
Detecting chip type... ESP8266
Chip is ESP8266EX
Detected flash size: 1MB

The cip supports external FLASH via SPI up to 16MB. You can find 1MB or 4MB versions.

Dowload firmware:
https://www.espressif.com/en/support/download/all?keys=8266 pick ESP8266 NONOS SDK
Direct link: https://codeload.github.com/espressif/ESP8266_NONOS_SDK/zip/refs/tags/v3.0.6

extract and go into /bin

esptool.py --port /dev/ttyUSB0 --baud 115200 write_flash \
  --flash_mode dout --flash_size 1MB \
  0x00000 boot_v1.7.bin \
  0x01000 at/512+512/user1.1024.new.2.bin \
  0xFC000 esp_init_data_default_v08.bin \
  0x7e000 blank.bin
  0xfe000 blank.bin

Make a backup:
esptool.py --port /dev/ttyUSB0 read_flash 0x00000 0x100000 esp8266_at_backup.bin
Restore backup:
esptool.py --port /dev/ttyUSB0 write_flash 0x00000 esp8266_at_backup.bin

Connect to ttyUSB0 you can use CuteCom. Use speed 115200 and at INPUT select CR/LF.
Commands: 
https://docs.espressif.com/projects/esp-at/en/release-v2.2.0.0_esp8266/AT_Command_Set/index.html
AT
Ouput: OK

AT+GMR
Output:

AT version:1.7.6.0(Jan 24 2022 08:56:02)␍␊

SDK version:3.0.6-dev(072755c)␍␊

compile time:Jun 17 2024 07:38:00␍␊

Bin version(Wroom 02):1.7.6␍␊

AT+CWMODE?

→ shows current Wi-Fi mode:

• 1 = Station

• 2 = SoftAP

• 3 = Both

Set to ap : AT+CWMODE=1

Scan for networks: AT+CWLAP
Connect: AT+CWJAP="YourSSID","YourPassword"

Show ip: AT+CIFSR

These are saved even on reboot.

Next section must be sent on every reboot:

Step 1 — start a TCP connection to a remote device
AT+CIPMUX=0

AT+CIPSTART="TCP","192.168.1.50",8888

Step 2 — enter transparent (bridge) mode

AT+CIPMODE=1

AT+CIPSEND

Compile and configure ESP3D as a Serial UART to WIFI Bridge

git clone https://github.com/luc-github/ESP3D.git

Configuration before compile:

ESP3D/platformio.ini   --- add to the end of the file

[env:esp01_1m_bridge]

platform = espressif8266@4.1.0

board = esp01_1m

framework = arduino

monitor_speed = 115200

monitor_filters = send_on_enter, colorize, esp8266_exception_decoder

board_build.f_cpu = 160000000L

board_build.f_flash = 40000000L

board_build.flash_mode = dout

board_build.ldscript = eagle.flash.1m.ld

upload_resetmethod = ck

upload_speed = 115200

extra_scripts = pre:platformIO/extra_script.py

build_flags =

    -D ESP3D_BRIDGE            ; enable bridge mode (no web UI)

    -D PIO_FRAMEWORK_ARDUINO_LWIP2_LOW_MEMORY

    -DNONOSDK221=1

    -DNDEBUG

    -DVTABLES_IN_FLASH

lib_ignore =

    ESP32SSDP

    TFT_eSPI

    esp32-usb-serial

ESP3D/esp3d/configuration.h

uncomment and replace xxx with your router data

#define STATION_WIFI_SSID "xxx"

#define STATION_WIFI_PASSWORD "xxxxxxxxx"

Optional if you want better speed

ESP3D/esp3d/src/core/esp3d_settings.cpp

#define DEFAULT_BAUD_RATE "230400"

#define DEFAULT_SERIAL_BRIDGE_BAUD_RATE "230400"

Compile

====

python3 -m venv platformio

source platformio/bin/activate

pip install platformio

cd ESP3D

platformio run -e esp01_1m_bridge --target clean   
platformio run -e esp01_1m_bridge

Upload firmaware

====== dont forget to have IO0 to GND and reset before uploading 

esptool.py --port /dev/ttyUSB0 flash_id

esptool.py --port /dev/ttyUSB0 erase_flash

esptool.py --port /dev/ttyUSB0 write_flash 0x00000 .pioenvs/esp01_1m_bridge/firmware.bin

If you want more speed use a ESP32

git clone https://github.com/luc-github/ESP3D.git

build_flags =

    -DESP_SERIAL_BRIDGE
    -DCONFIG_FREERTOS_HZ=1000

platformio = pio (same command)

pio run -e esp32dev
pio run -e esp32dev -t upload

ESP_LINK for ESP6288

Go to https://github.com/jeelabs/esp-link/releases

Download: http://s3.voneicken.com/esp-link/esp-link-v3.2.47-g9c6530d.tgz

Connect the esp6288 to usb (either via usb or usb-to-ttl converter) then flash.

esptool.py --chip esp8266 --port /dev/ttyUSB0 --baud 460800 write_flash \

  -fs 1MB -fm dio -ff 40m \

  0x00000 boot_v1.6.bin \

  0x01000 user1.bin \

  0x3fc000 esp_init_data_default.bin \

  0x3fe000 blank.bin

Micropython esp32 urequests and TFT

I installed micropython on my esp32 for easier coding - no more waiting for the arduino code to recompile, and easy testing of new code.

All good for now.
A few problems started to appear.
When using a LCD a ST7735 the refresh is very slow, you can see the screen being painted from top to bottom. Its not terrible but not that great, on arduino with C code was fine.

Second problem, when I tried to log some data online with urequest, or even with sockets.
I started to get: OSError: (-29312, 'MBEDTLS_ERR_SSL_CONN_EOF')

The problem comes from SSL part - if the server is using anything more powerfull then RSA for the HTTPS certificate we have a problem.
ESP32 is left with too little memory and cpu from running micropython.

Two solutions.
If you remove the TFT library it works, but this is not really a solution, since I want the data displayed on the screen as well.

I went through the library and started to remove pieces of code not required, like they have 3 functions to initrb, initrg, initrr - to initialize the screen with red, green or blue. Just keep the red one and remove the others.
I also removed the drawing functions like circle, line, rect etc - I only needed text.
After this trimming, I got the first success, urequests actually working, but not all the time.

So second solution was to ditch the HTTPS.
Setup the server to accept http. Then it works fine.