I designed a wearable device for rehabilitation and sport training, using BNO055 as sensor. Prototypes and first production lot went good, while the second lot had a huge percentage of failing items. Just two seems really damaged as signals look disturbed and a noisy 1.6V is found on pin 9 instead of a clean 1.2V. Most of the other items simply are not answering on I2C bus in the application, but the same interface grants the ACK if the chip is put in BOOT mode. I think the internal program is somehow lost. Questions are: - is my assumption likely? if yes, what could be the most probable cause of that: wrong temperature profile, ESD, or ? - is it possible to reflash these items without desoldering? (I have access to pins 4, 10, 11, 14, 19, 20 while pins 5,6,17,18 are grounded) Thanks for (even partial) replies! MF
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