Esp-01 01s Extra Quality Jun 2026

Most USB-serial adapters with DTR/RTS can automate this (e.g., NodeMCU flasher).

When you use Serial.begin() , GPIO1 (TX) and GPIO3 (RX) are taken over by serial communication. If you need extra pins, disable serial debugging after boot using Serial.end() . You will then have a total of 3 usable GPIOs (GPIO0, GPIO2, GPIO3/RX). esp-01 01s

| GPIO | Safe to use? | Notes | |------|--------------|-------| | GPIO0 | Yes | Pull-up required. Low at boot = flash mode. | | GPIO2 | Yes | Pull-up required. High at boot. | | GPIO1 (TX) | No | Serial debug. Low at boot = crash. | | GPIO3 (RX) | No | Serial input. | | GPIO16 | Not broken out | Deep sleep wake (connect to RST). | Most USB-serial adapters with DTR/RTS can automate this (e

To put the ESP-01S into flash mode , you must manipulate the GPIO0 pin during boot. You will then have a total of 3

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: Can operate as a Station (client), Access Point (hotspot), or both (AP+STA).