Internal pull up on I2C bus

RE: Internal pull up on I2C bus

Dmitry — Tue, 10 Nov 2020 16:31:43 GMT

They're enabled by default by the TWI driver.

RE: Internal pull up on I2C bus

BIBINLUKOSE — Tue, 10 Nov 2020 16:29:05 GMT

We are programing Nordic first and MSP is the slave and nordic will pull mSP in to BSL mode.

My question is , the pullup on Nordic I2c is by default or it need to be enabled through boot loader?

RE: Internal pull up on I2C bus

Dmitry — Tue, 10 Nov 2020 16:18:57 GMT

Also look at this discussion - the real test of i2c with internall/external pull-ups.

RE: Internal pull up on I2C bus

Dmitry — Tue, 10 Nov 2020 16:12:30 GMT

If you're asking about MSP430 side - I have no idea (one can guess - no, as BSL don't know which interface will be used beforehand)

RE: Internal pull up on I2C bus

BIBINLUKOSE — Tue, 10 Nov 2020 15:16:19 GMT

Response from FW team: We have not control over the BSL boot rom so we cannot enable internal pullups.

By default are these pullup enabled? how does it get enabled in BSL mode?

RE: Internal pull up on I2C bus

Dmitry — Tue, 10 Nov 2020 09:06:48 GMT

Hi,

for 52840,an internal pull-up resistance is in range 11-16 kOhm. The maximum speed depends also on load capacitance of i2c bus components. According to appnote from TI (google by "i2c pull-up resistance"), to achieve reliable communication in standard mode with 16k, load capacitance should not exceed ~70pF. If MSP430 is the only device on the bus and trace length is quite short, everything should work fine. If you need fast mode communication, you should put externall pull-ups anyway.

By the way, MSP430 also has internal pull-ups that could be handy.