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WICED Smart Bluetooth

Anonymous
Not applicable

Good morning

BCM20737S have internal EEPROM and mapped to the only available I2C bus (available externally).

I would to know what are the internal i2c pull-up value and order to adjust my external one.

in the TAG3 board, 2.2kohms are mounted. In WICED sense there is 10kohms through I2C bus expander.

What are really required please ?

i have plenty of sensors mapped to BCM20737S and i would like to be sure about my external pullup values.

i didn't see anything on the BCM20737S reference manual.

thank you a lot

best regards

Etienne

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1 Solution
Anonymous
Not applicable

Hello E L,

Both SDA and SCL have been pulled up with 10K ohm internal to the BCM20737S

Thanks

JT

View solution in original post

6 Replies
Anonymous
Not applicable

Hello E L,

Both SDA and SCL have been pulled up with 10K ohm internal to the BCM20737S

Thanks

JT

View solution in original post

MichaelF_56
Moderator
Moderator

For others that may come across this thread in the future, we should also note here that the I2C spec requires an external pull up on SCL and SDA.  The internal pullup is not sufficient because the part will not be configured until an I2C slave is detected (i.e. external pullup), which is a chicken-egg situation.

This only applies to the SoC. The pullups inside the SIP modules (shown on the internal schematic) are still external to the die, so the modules don't need pullups outside the module.

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JeDe_2143696
New Contributor II

Hello,

you said that sip modules don't need pullups outside but on the wiced sense design, external pullups of 10K are presents, are these really usefull ?

best regards

JP

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MichaelF_56
Moderator
Moderator

The I2C spec requires an external pull up on SCL and SDA.  The internal pullup is not sufficient because the part will not be configured until an I2C slave is detected (i.e. external pullup), which is a chicken-egg situation.

Note that this only applies to the SoC (WICED Sense uses a SIP). The pullups inside the SIP modules (shown on the internal schematic) are still external to the die, so the modules don't need pullups outside the module.

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Anonymous
Not applicable

First of all, I'm sorry that I can't understand completely your English, mwf_mmfae because I'm not good at English.

In short, BCM20737S SIP doesn't need external resisters because SIP has internal resisters the value of which are 10k ohm inside.

Is this correct?

Best regards

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MichaelF_56
Moderator
Moderator

The BCM20737S SIP module does not require pullups outside the module.

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