If you need a general paper on for embedded systems, I can write that from scratch using standard references.

While Growatt is the most common association for version 4.20, "ISP Tool" is a generic name used by several manufacturers. For instance, uses a similarly named utility for door controllers, and Genesys Logic uses one for USB hubs. Growatt SPF5000ES Firmware Upgrade - Greenrich

: Most updates require you to reset the inverter to factory settings or reconfigure the model and serial number after the flash is complete. Troubleshooting

Security considerations