AHT10 - I2C problem

I just bought AHT10 humidity and temperature sensor. I have seen that it supports I2C and it is cheap so I didn't think thoroughly and bought two. I wanted to try them then I encounter a problem that only a single AHT10 can be connected to single I2C bus. I thought it is related to static address but it is worse (breakout board also showing two address but no details in the datasheet). The datasheet says that "Only a single AHT10 can be connected to the I2C bus and no other I2C devices can be connected." It sounds like traditional serial communication like RS232 not I2C.

Is it normal to advertise it as an I2C device? and I also wonder what is the technical issue preventing to connect other devices with different address. Did you have any experience similar to this on any other sensor?

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beacon_dave over 2 years ago

It might be possible to use two or more AHT10 devices with a 'chip select' type setup.

The AHT20 data sheet shows a power control application design like this for power saving applications which may be able to be applied to the AHT10:

'GND_CTRL' effectively becomes a chip select line allowing you to activate the device you want to communicate with using the same I²C addresses.
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BigG over 2 years ago in reply to beacon_dave

Both datasheets (AHT10 & AHT20) show that the sensor operates on microAmps, so powering by GPIO is possible too...
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BigG over 2 years ago in reply to beacon_dave

Both datasheets (AHT10 & AHT20) show that the sensor operates on microAmps, so powering by GPIO is possible too...
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beacon_dave over 2 years ago in reply to BigG

That design disconnects the I²C bus pull-up resistors from VDD presumably to prevent current drain through the pull-ups and driver IC to ground in power saving applications.

If not concerned about power saving, then another approach may be to leave the sensor powered and look at connecting/disconnecting the SDA/SCL lines from the I²C bus with the 'chip select'.

Keeping the sensor powered may improve measurement accuracy if it requires time to stabilise after power up. Although a 'chip deselect' approach may also work here or simply factoring in stabilisation times prior to a measurement.
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msimon over 2 years ago in reply to BigG

Hi BigG, I will try it to see it works or not. Sounds logical but I am not sure if the product brings other problems.
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msimon over 2 years ago in reply to beacon_dave

Hi beacon_dave , it takes around 20 ms to reach idle state. I am gonna use it measure hive temperature. So power efficiency is more important than the timing. I will try to select the sensor with power line and see how it works.
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msimon over 2 years ago in reply to BigG

I connected two sensors on the same bus and then connect their Vin pins to GPIO. I also attach another I2C sensor TMP102. It looks like working but there is a reliability issue. Sometimes it stops. I also suspect the serial port of Arduino IDE. I will check that.
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