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AMC6821: I2C issues with Intelligent Temperature Monitor and PWM Fan Controller

Part Number: AMC6821

I have grounded address lines A0/A1 and hence I'm sending the 8-bit Slave address of 0x18 from my microcontroller to the AMC6821 chip.  On a CRO I can see the pulses on the SCLK and SDA lines so I know I'm clocking data in and out.

However whenever I try to read a byte from any of the registers (following Table 7 format in datasheet) they are always returning 0xFF.

At the very least for Device ID Register (address=0x3D) I should read a default value of 0x21 and the Company ID Register (address=0x3E) should read a default value of 0x49.  These are read-only registers so there is no way I could have accidentally overwritten them.

Is the IC faulty or something, or am I doing something wrong in using the i2c bus?  I have attached the circuit diagram below.

  • In reply to Chris Reed1:

    Chris,

    Did you figure out the issue? Sorry for the late response.

    -Kelvin
  • In reply to Kelvin Le THS:

    More or less yes - thanks Kelvin.

    It turns out the IC was faulty and when we replaced it we could control it, albeit at a basic level.

    If I had more time I would look into the closed loop control of the fan, but for now we are just setting a PWM value and that does what we need for now.

    Chris

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