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BQ76940EVM: Unable to detect the BQ76940 chip on the I2C bus

Eohan George22
Intellectual 620 points
Part Number: BQ76940EVM
Other Parts Discussed in Thread: BQ76940,

Hi, 

We are trying to talk to the bq76940 chip on the bq76940evm board. However, using an arduino to check on the i2c bus does not detect the particular 0x08 or 0x18 address for the BQ chip. I've ensured that the cell simulator is switched on with the orange led lit. The jumpers for SDA and SCL pull up are also plugged in. 

The boot pin button enables the bq chip(seen by detecting a 2.5v on the pull up line)

  • 0
    TI__Guru 54715 points
    Hi Eohan,
    The standard part on the EVM is address 0x08.
    Be sure the gauge is disconnected from the I2C. You might check that the TI adapter still talks to the BQ76940. Using a scope, look at the I2C signals on the board. Compare the structure of the waveforms between the TI adapter and the Arduino. The Arduino is likely much faster, check that the clock is not too fast, but basically look for the bit structure including ACKs & start/stop, and also the signal levels.
    One common point of confusion: The 7 bit 0x08 address is shifted left for the read/write bit in I2C, on the bus it will appear as 0x10 or 0x11. I'm not sure how the Arduino handles that, but it is good thing to check.