Enabling a Pull up resistor in the 5438A and I2C example

netrover

Other Parts Discussed in Thread: MSP432WARE

I am trying the I2C example to control a camera. The camera's docs say that the two I/O pins (called 'SCL' and 'SDA') need pull up resistors.

The example in the MSP432ware for the 5438A that we have uses GPIO_PORT_P3, GPIO_PIN1, and GPIO_Pin2, while any document I see generally would use P3SEL and P3DIR. And the pullup resistors are set with P3REN for BIT1 and BIT2 or probabl use in hex, 0x06.

Can I still use P3REN to enable pull up resistors for the port pins 1 and 2? I want to make sure this is correct as a known for debugging possible other problems.

Thanks

over 11 years ago

0 Leo Bosch over 11 years ago

Guru 23000 points

You can enable the internal resistors but they will be probably too weak for a proper pull-up. Use external resistors 4K7-10KOhm.

0 netrover over 11 years ago in reply to Leo Bosch

Intellectual 850 points

Will try them.
Thanks,
Dan

0 Jens-Michael Gross over 11 years ago in reply to netrover

Guru 227245 points

On 5x family, the pull-ups are disabled when a port pin is in output direction.
It's not 100% clear if the I2C pins are switched between low output and input or (as the users guide says) are used as OC outputs. In the latter case, the pull-ups are not available at all, in the first case, they are inactive during low output, and may cause bad signal edges. In any case, they are too weak for proper I2C operation.

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Enabling a Pull up resistor in the 5438A and I2C example