TESS-W4C is a variant of TESS-W with four channels. Three other channels are added to the integral channel to have RGB. Like the one-channel models, this photometer sends the readings to the STARS4ALL network , and in parallel it can also be consulted locally.
The firmware compiled for the update is a .bin file. Here is the latest version. The tool ESPFlash_DowloadTool is used to load the update. A version is included here, just unzip and run. Details in the pdf.