Closed charlespax closed 7 years ago
I made a graph showing the pullup resistor range for 100kHz and 400 kHz.
We should keep the pullup resistors values as low as necessary to allow for a larger enough bus capacitance range. This is because the modules affect the bus capacitance.
I wonder if the internal pullup resistors were enabled on the i2c lines. That would explain why we needed such a high value on the external resistors; the internal and external resisotrs might be running in parallel. Does the STM32F103 even have internal pullup resistors for the i2c lines?
I'm keeping the 1.5k in the design for now. When revision 4 comes back I will try different values. See i2c pullup resistor test #135
Redo calculations and find what would be a good value. Can we even have a fixed value without knowing the total capacitance on the lines?
We could go nuts and use digital pots.Notes