A small change allows you to activate the DFU mode with the jog key, just like on tinySA Ultra or NanoVNA-H4, by pressing the jog key while turning on the tinySA. After power on the device is in DFU mode and the screen should stay white. This makes it possible to always enter DFU mode without opening the device - even if the loaded firmware is not responding.
You just have to make a wire connection from the BOOT0 connector of P1 on the side of the PCB to the middle contact of the jog switch.
This gives a measured level of about 1.7V on BOOT0 when jog switch pressed, slightly above the required minimal high level VIH:
BOOT0 VIH >= 1.61V (0.2 VDDIOx + 0.95V)
according to STM32F072x8 STM32F072xB Datasheet - September 2019 - DS9826 Rev 6 - p.78/128
?
?
?