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  • Good display but it is not I2C compliant

    posted by [email protected] on 06/25/2015

    Impression:Good product,Good display;

    It is definetly a good display with good quality. It is based on driver TM1637. The datasheet is in chinese, but you can easily find working firmwares around that you can just copy. The example in the chinese datasheet works fine as it is readable (it is in C).
    The only problem with this device is that IT IS NOT I2C COMPLIANT. I have found at least two differences: first, the less significant bits are sent first, while in I2C is just the opposite. The ack follows a different handshake. All this means that you cannot use the I2C peripheral of your micro; instead, you must drive yourself the data and clk signals. It is easy because the example in the datasheets already do this.

    Since it is not a real I2C device, it may conflict with other I2C devices in the same bus, in fact, it already provides the 10K pull-ups for stand alone use. Nontheless, I do have this device in the same I2C bus as other devices and, as long as the addresses of the real I2C devices do not match some words used by the TMS1637, everything is almost fine, becase the TMS1637 does not filter the messages sent to other devices and process them all (you have to see if it is a problem or not). In my case, the display shows garbish while the I2C is used by other devices, but at least it does not hang (so far).

    If you want a stand alone good display that uses a very simple two-wire interface, this is your display. If you want a real I2C device in a sharing I2C environment, this is not your display (though it may work in some circunstances).

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