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[FAQ] INA229: Registers are reading incorrectly

Louis L
Expert 6870 points

Part Number: INA229
Other Parts Discussed in Thread: INA239

Why is it when I try reading a register, it appears that I'm actually reading a completely different register? For example, I read 0x3F but I get the results from register 0x3E instead.

  • 0
    TI__Expert 6870 points

    A common error with this device that causes read/write values to be different than expected is to be using the incorrect SPI MODE. The INA229 uses CPOL = 0 (The clock is low (inactive) when idle and data is sampled on the falling edge) and CPHA = 1 (Data is shifted on the rising clock edge).

    The 4 modes for SPI are

    • SPI Mode 0 (CPOL=0, CPHA=0): Idle low, data sampled on rising edge, shifted on falling edge
    • SPI Mode 1 (CPOL=0, CPHA=1): Idle low, data sampled on falling edge, shifted on rising edge
    • SPI Mode 2 (CPOL=1, CPHA=0): Idle high, data sampled on rising edge, shifted on falling edge
    • SPI Mode 3 (CPOL=1, CPHA=1): Idle high, data sampled on falling edge, shifted on rising edge

    Both of our SPI current sensors, the INA229 and INA239, use SPI Mode 1