I am using an Arduino on a breadboard setup with an ATMEGA328p MCU. The whole circuit is designed to work in a low-power state and is powered using a 3 V (nominal) Coin Cell.
The HC-SR04 is getting a stable power supply of 5 V from another source (grounds are already common).
However, the issue is that triggering the sensor from the MCU gives no output reading and the distance is returned as 0. I checked the voltage level on the trigger pin and found it to be 2.5-2.6 V
Since the battery I am using is a coin cell I suspect that the voltage is dropping from the nominal value of 3 V to 2.5 V and the HC-SR04 demands a TTL pulse on the trigger pin. Is it not working because it's not being properly triggered by the 2.5 V pulse? I checked some resources and they mentioned that 2.5 V is within the High Level Margin of the TTL signal, so a 2.5 V level pulse should be able to trigger the sensor. Or is my assumption wrong?