Makers
For a MusicBox you built yourselfYou have built your MusicBox and you are installing the software from the Software page. Here is what the messages you may come across there mean, and what the MusicBox says at startup.
The browser
Flashing goes through the Web Serial API: you need Chrome, Edge or Opera, on a computer. Safari, Firefox and mobile browsers do not offer it.
The page puts the board into flash mode on its own: it does not ask you to press any button.
"Could not open the serial connection"
The browser could not open the chosen port. Check the cable, plug the board back in, and choose its port again in the browser window. Closing that window without choosing shows no error.
"The flash failed"
The download, the switch to flash mode or the writing stopped. The detail is in the serial monitor, on a line starting with [flash] error. Start the flash again.
If the message says the boot slot could not be reset, the software was written correctly but the board may restart on the previous version: start the flash again.
Erasing everything, or not
The "Erase everything before flashing" option is for a first install. It also erases what the board had saved, including the Wi-Fi. Without it, those settings are kept.
"The MusicBox still isn't answering"
After the flash, the page waits for the MusicBox to finish starting up to read its access code. That takes about thirty seconds, and the page waits up to forty.
If nothing answers, it is often because there is no software on the board yet: flash it in step 2. If it was disconnected while the code was being read, reconnect it in step 1.
Reading the startup log
The serial monitor shows the startup step by step. Three lines matter: [1/3] for the microSD card, [2/3] for the audio, [3/3] for the NFC reader.
If the microSD card or the audio fails, the light blinks slowly in red. If only the NFC reader fails, the MusicBox starts without it and no light signals it: only the [3/3] line tells you.
The software requires an ESP32-S3 N8R8, with 8 MB of PSRAM. On a board without PSRAM, startup stops on a FATAL line that says so.
Before asking for help
Tap "Copy" in the serial monitor and attach the lines to your message: they almost always say where it gets stuck.
Guide checked on October 29, 2026 against the MusicBox software of that day.
Still stuck?
Write to us on Discord, we answer.