All 4 ESP-01 have been tested with the flicker circuit and all work fine. So far I've made an IOT button with one and it's been working for a week now. You can find them cheaper but nothing beats 2 day shipping! I used a serial USB ESP8266 wifi module for programming along with a soldered button to enter programming mode.
TRENDnet TC-TP1 Network Signal Testing Probe with Adjustable Volume, Speaker and Compatibility for TC-NT2
8 Review
π Ximimark 1Pcs ESP8266 Network Relay WIFI Module 220V 10A DC 7-30V 4 Layers Board TVS Input Automatic Protection: Enhanced Home Automation Solution
8 Review
π‘ Izokee ESP-01 Serial WiFi Transceiver Module with USB Converter, Compatible with Arduino
8 Review
πΆ kuman 10pcs nRF24L01+ 2.4GHz Antenna Wireless Transceiver Module for Arduino Raspberry Pi Compatible K19
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HB-UMLS Sabrent USB 2.0 Hub with 4 Ports and LED Power Switches for Each Port
12 Review
UGREEN USB 3.0 Ethernet Adapter Hub with RJ45: Fast Gigabit Ethernet Converter, 3 Ports USB 3.0 Hub Compatible for MacBook, iMac, Surface Pro, Chromebook, Laptop, PC
11 Review
π USR-TCP232-410s: RS232/RS485 Serial to Ethernet Adapter/IP Device Server with DHCP/DNS Support
4 Review
π StarTech.com NETRS2321P: 1-Port RS232 to Ethernet IP Converter, Serial over IP Device Server - Black
5 Review