root@hasrv:/tmp# esptool.py --before default_reset --after hard_reset --baud 460800 --chip esp8266 --port /dev/ttyUSB0 write_flash 0x0 /tmp/sonoffbasic01.bin
esptool.py v2.7
Serial port /dev/ttyUSB0
Connecting....
Chip is ESP8285
Features: WiFi, Embedded Flash
Crystal is 26MHz
MAC: dc:4f:22:9e:b5:94
Uploading stub...
Running stub...
Stub running...
Changing baud rate to 460800
Changed.
Configuring flash size...
Auto-detected Flash size: 1MB
Compressed 424784 bytes to 290001...
Wrote 424784 bytes (290001 compressed) at 0x00000000 in 7.4 seconds (effective 458.6 kbit/s)...
Hash of data verified.
Leaving...
Hard resetting via RTS pin...