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.
- 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!
Thanks for your inquiry.
BNO055 comes to the market with fixed SW pre-programmed. This means that users don't need to reflash BNO055.
In your second lot of build you got a lot of failure BNO055 parts. Do you know the values in BNO055 register 0x04 and 0x05 for SW version? In addition, BNO055 is at allocation stage. Where did you purchase the second lot BNO055 parts?
To your questions:
- parts have been bought not directly from Bosch cause of the shortage; I can try to get more exact information about that
- are registers 0x04, 0x05 accessible also in boot mode (otherwise I could not answer you...) ?
- is the different behavior between boot and not boot mode enough for assume that the flash program is corrupted?
As you will agree, I'm asking about reflash in order not to waste several boards...
Please make sure that you purchase BNO055 from authorized distributors such as Digikey, Mouser, Arrow and Future, etc.
If you cannot read BNO055 registers 0x04 and 0x05 to find out the SW revision, then the BNO055 is not working. If you want to reflash BNO055, then you need to use Atmel Studio IDE, JTAG box, BNO055 FW image from Bosch and the extension board from Bosch. Please refer to https://www.bosch-sensortec.com/media/boschsensortec/downloads/application_notes_1/bst-bmf055-an001.... for more information.