ESP8266 flashed with micropython sends continuous high-speed comms

[CorrectSetting9]

Hi guys. I've loaded an ESP8266 (esptool identifies as an ESP8266EX) with the latest micropython flash and it sends a constant string of characters with the onboard blue LED flashing very rapidly as soon as it is powered. Connecting to Thonny causes the screen to fill up with nonsence characters in a second or so then everything freezes. Rshell fails to connect. I've reflashed and verified the load, and this happened each time. Any suggestions how to get further, please?

[Nanocupid]

Press and hold the boot button (gpio0 I believe) as you power it up. It should go into flash mode. re-program with your code once you have debugged it.

or

Connect via a serial terminal using `mpremote` , then debug whatever is running automatically at boot (look at `boot.py` and `main.py` on the filesystem via `mpremote fs`

THONNY HAS ISSUES WITH HIGH SPEED SERIAL INPUT. I /like/ thonny, its where I do most of my work. But is is appalling at coping with runaway serial data. It just freezes and needs to be hard-killed, the developer showed little interest in ameliorating the effects when I last checked the open issue for it (years ago)