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I have a humidity sensor that outputs humidity to my Arduino Uno. In order to send this value to my DAQ system, I am using an Adafruit MCP4725 Digital-analog converter(DAC), which turns the humidity into a voltage output. I have only the SCL and SDA bus on the Arduino, which according to the guide shouldn't be a problem. The guide says, " If A0 (Pin on DAC) is connected to VDD the address is 0x63. This lets you have two DAC boards connected to the same SDA/SCL I2C bus pins." My main question is, where is "VDD" on my arduino? My understanding from searching online and the datasheet is that VDD is the "high" voltage, but the 5V pin is taken up by my humidity sensor, so where should I connect it to use the same SDA bus? Thank you and sorry for the jumbled writing.

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VDD is the MCP4725 chip's supply pin name. I won't put the whole history of naming convention here but basically, VDD and VSS are general names for CMOS devices' supply voltages/pins.


VIN terminal is connected to VIN of the chip on the breakout board.

So you should tie A0 pin to VIN terminal to give the chip the alternate address.

To apply voltage to the breakout board (and your sensor) from Arduino, use Arduino's 5V pin, as indicated in the guide you linked. You can use the same 5V lane for different purposes i.e. one wire from Arduino's 5V to sensor, one more wire to breakout board's VIN, etc.

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  • \$\begingroup\$ Great, appreciate it! \$\endgroup\$ Nov 3, 2022 at 16:36
  • \$\begingroup\$ You can accept my answer (by clicking the tick button under the points section) if it's satisfactory enough, so that the question does not remain open. \$\endgroup\$ Nov 3, 2022 at 16:37
  • \$\begingroup\$ @LiamWarren, re "You can accept my answer...". But it is recommended that you wait to see if other answers are posted, in case you think one answers the question better, rather than quickly accepting the first answer in the first few minutes. \$\endgroup\$
    – TonyM
    Nov 3, 2022 at 17:44

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