Factory flashing of firmware

[jhbruhn]

Hi! I am in the middle of "porting over" the HA Voice PE hardware design to a Google Home Mini compatible PCB (Onju Voice v2 one may say).

The XU316 has its own flash memory chip. The XMOS firmware which is delivered with the voice-pe is residing in that flash an can be reprogrammed by the ESP32 via I2C-DFU.
But this DFU is implemented in the voice-pe-XMOS-firmware. The XU316 does not come with a boot-ROM which can be used like with the ESP32 to do the initial programming, does it?
How are you doing the initial flashing in the factory? Preprogrammed flash-chips, or programming via the JTAG connector?