Using SDA to read Analog data from Honeywell ASDXACX100PAAA5

I've been looking at using 4 Honeywell ASDXACX100PAAA5 sensors in a pneumatic system to monitor pressure with a Teensy 4.1. Is it possible to use the SDA line from the sensor as an analog output to read from so I don't need to use I2C to interact with the sensor?

The datasheet I looked at stated these sensors are analog output 0.5 to 4.5 Volts

Note the 5 at the end.
This ratiometric 5volt-only sensor is not compatible with a 3.3volt-logic Teensy.

If you want to use the SDA line use it as an analog input, not SDA which is digital. With the map command you can change the 0.5 to 4.5 volts to whatever you want. Note the 4.5V will not be 1023 it will be lower as the reference is connected to the Arduino 5V.

xxxAA5 means an analogue 5volt sensor with 10-90% ratiometric output.
It does not have an SDA line, and is not Teensy (3.3volt) compatible.


My Goof I was thinking of another arduino part. I understand that is analog. If it were an UNO that answer would have been correct however in this case I was wrong. Also he has to scale the voltage down as it is not 5V tolerant.

How would I scale the voltage down from 5V to 3V? Is there anything else I would need to do to make the sensor usable on the Teensy 4.1?

Use a resistor divider. This link will help you calculate it. A 2K and 3.1K resistors will do it for you. It will be just over 3V but within the 3.3 Volt limit. You can play around with resistance values and get what you want. You can buy "voltage sensors" for the Arduino but normally they are just resistors. Your sensor will replace the battery. R1 would be 2K R2 would be 3K where they connect goes to the analog input of the micro.

So have the resistors attached to the supply and ground (2K on one and 3.1K on the other) and just read from the sensor?


Your battery replaces the sensor and the Output goes to the A/D. I took this drawing from the calculator, hopefully it helps.

Not sure what you're saying, I'm pretty new to Arduino.
Is there any way to use the sensor? What battery are you talking about and what is the A/D?

Not as simple as that.
The sensor readout would then also depend on sensor supply voltage, which you don't want.
Just buy the right sensor for 3.3volt logic (with a "3" at the end).
Or use a 5volt Arduino.

The sensors have already been ordered so I need to use them, is there any way to increase/decrease the voltage to/from sensors to make it work w/a Teensy?

Use a 2:1 voltage divider on the output of the sensor, and live with fact that pressure now also depends on the 3.3volt Teensy and 5volt sensor supply fluctuations.

Or also measure the 3.3volt and 5volt supplies, and add code that compensates for those fluctuations.
Good luck.

1 Like

The device is rated at Voltage - Supply of 4.75V ~ 5.25V. There is a reason the manufacturer specified that voltage, they guarantee its performance. The sensor supply voltage has no relationship as to what micro you use. If that sensor is going to be used the micro has to be chosen to tolerate the voltage from the sensor or the output voltage has to be scaled to the micro. If you have worries about a resistor divider look at how the scale voltage in a multimeter. Your voltage devicer can be whatever ration you want, just be sure it does not output more voltage then the micro can tolerate. In the end it comes to the number of A/D counts you can get for your range.

1 Like