Part Number:MSP430F5528
High, I am using the UCB1 peripheral in the I2C mode, via the TI-RTOS driver. The module is always operated as a master with one slave device on the bus.
My slave device specifies a minimum fall time of 20 nS, a maximum rise time of 300 nS, on the SCL and SDA signals. Both of my pullup resistors are 3.32K ohms and are connected to the 3.00V supply.
Using my scope I have measured a fall time of 1.8 nS on both of these signals. Using the emulator, I have checked the drive strength settings in the register P4DS. The register has a value of 0x00, indicating that P4.1 and P4.2 are both set for reduced drive strength.
Attempting to increase the fall time, I connected a 47 pF cap between each signal and ground. Now I measure a fall time of 4nS on both signals. Still way too fast.
My rise time is good at 172 nS.
What is the best way for me to achieve the correct fall time ?
Thank you for your time.
Roy