As others have said, to write to the ESP-01 you need to add a switch to ground GPIO 0 at power up. Not only did I add the GPIO 0 button, I also added the reset button. With a little twisting finger maneuver I can 1) press the reset button, 2) press the GPIO 0 button, 3) release the reset button, then 4) release the GPIO 0 button. With this technique, I don't have to take the whole thing out and put it back in every time I want to write. Requires two buttons on the board and some 30 gauge winding wire. A 5-star module does not require mods. :)
π‘ CM19A R.F. PC Transceiver for X10 Devices
8 Review
MikroTik S+RJ10 Ethernet Transceiver
10 Review
π Gigabit Ethernet Media Converter, Single Mode Dual SC Fiber, 1000Base-LX to 10/100/1000Base-Tx, up to 20km, 2-Pack
9 Review
10GBase-T SFP+ Transceivers, 10G Copper RJ-45 SFP+ CAT.6a, up to 30 meters, π Cisco SFP-10G-T-S Compatible, Ubiquiti UniFi UF-RJ45-10G Supported, Fortinet, Netgear, D-Link, Supermicro (Pack of 2)
9 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
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 Juiced Systems Silver BizHUB USB-C Multiport Gigabit HDMI Hub with 3 USB 3.0 Ports, Gigabit Ethernet, 4K HDMI, SD/Micro SD, and USB-C Power Delivery
11 Review