This board has everything you need to communicate with ESP8266 by USB over serial TTY.
It is build around CH340 chip what usually needs to install drivers on a computer. After restart you can connect it with ESP-01 on it to USB and see what device was added to /dev (on UNIX systems), it should be lomethink like /dev/tty.wchusbserial123.
$ ls /dev/tty.wchusbserial* /dev/tty.wchusbserial410
Then you can connect to it and send some AT commands:
screen /dev/tty.wchusbserial410 115200
If you want to load some alternative firmware into it you have to boot into flashing mode. Some convertors of this kind has switch for it, but most does not have so usually you have to wire GPIO 0 to GND by yourself.
I soldered this bridge for it:
You can be creative how you wire GPIO 0 to GND, just it is good to make it reversible, because you probably will need to boot it also in normal mode.
Then you should be able to clean flash and write firmware:
$ esptool.py -p /dev/tty.wchusbserial410 -b 115200 erase_flash esptool.py v1.1 Connecting... Erasing flash (this may take a while)...
Disconnect if from USB and connect it back (reset).
$ esptool.py --port /dev/tty.wchusbserial410 --baud 115200 write_flash --flash_size=8m --verify 0 esp8266-20160910-v1.8.4-9-gdd0e6dd.bin esptool.py v1.1 Connecting... Running Cesanta flasher stub... Flash params set to 0x0020 Writing 532480 @ 0x0... 532480 (100 %) Wrote 532480 bytes at 0x0 in 46.2 seconds (92.2 kbit/s)... Leaving... Verifying just-written flash... Verifying 0x818b4 (530612) bytes @ 0x00000000 in flash against esp8266-20160910-v1.8.4-9-gdd0e6dd.bin... -- verify OK (digest matched)
Disconnect from USB, remove “flashing mode bridge” and connect it to USB back and new firmware should boot.