While testing the signals with the oszi, it works.
Maybe of the capacity of the probe (100pF) on SCL to GND.
But after further tries, it also works with only probe connected to SCL (no GND). And later also with no oszi connected (just the probe, no GND).
Schematic? Maybe something in the support circuitry of the Bosch BMA020 pcb?
I see the board has a wider voltage range than the BMA020 chip itself, so something must be going on there...
Also, be sure there are no external pull-up resistors activated on the I2C bus connected to the DUE. The pull-ups are already included on the DUE, and are aggressively sized (on the small end). Additional current due to improperly-sized external pull-ups will destroy the DUE's I2C hardware interface. Anecdotally, I believe that I have destroyed DUE's TWI by just activating the TWI, and inadvertently leaving the logic states low on either/both of these pins, using the built-in pull-ups.
FWIW: I have a I2C DUE system that works reliably with 13 addressable gateways, each with I2C subnets beyond. So, the TWI hardware does work. However, I do buffer the network.
thanks for your ideas, but unfortunately it does not help.
The module which carries the BMA020 has a level shifter.
I have no external pull-ups (I know they are included on DUE).
I use several other I2C chips single and combined on the DUE.
What's not clear to me, why helps the oszi probe?
Now I use a 33pF SCL to GND. And it works.
thanks for your ideas, but unfortunately it does not help.
The module which carries the BMA020 has a level shifter.
I have no external pull-ups (I know they are included on DUE).
I use several other I2C chips single and combined on the DUE.
What's not clear to me, why helps the oszi probe?
Now I use a 33pF SCL to GND. And it works.
Sounds for me at all there is ground missing on the BMA020 may somewhere is the ground connection broken by some wire
Sounds for me at all there is ground missing on the BMA020 may somewhere is the ground connection broken by some wire
IMHO the wire could not be the problem, because all measures and the capacitor were connected directly on the DUE and not the BMA020.
On the other hand, a cap could not supply the BMA.
Measure of the wires results in low resistance and no short circuit.