I would like to submit my completed circuit for review. Please take a look!
I am using an ESP32-C3 MCU, which would be powered by 2 AA batteries through a soft latch circuit and a step-up circuit. The ADC conversion would be done by an ADS1115 chip, and the display would be an SSD1306 OLED screen. Both communicate with the MCU via the I2C interface.
You can find an overview of my struggles with the latching circuit in the following topic.
The ADS1115 and SSD1306 modules may already have some pull-ups on-board. You may not need or want to add more on your PCB because if you added another i2c device which also has pull-ups on board, the combination of all 4 sets of pull-ups might be too strong and prevent the devices from working.
Why are you stepping up the battery voltage to 5V? I don't see any devices here that need 5V, they all need 3.3V, I think. If so, stepping up to 5V only to regulate down to 3.3V will only waste some of the battery's capacity.
In the datasheet of the ADS1114, it mentions the use of two pull-up resistors (page 34). The 3.3V input voltage is justified, it's just that this 5V voltage regulator was on hand, but a fixed 3.3V output step-up converter really is simpler and more logical!
Are you using a bare ads1114 chip on your PCB? Or a module containing the chip?
I have some ads1115 chips on modules, and these have 10K pull-ups on-board.
With your struggles with the latching circuit, I got the idea you truly want to get maximum life out of your batteries, but if you want to use a component that will be inefficient because you already have it, I guess I was mistaken. The regulator on the esp board is going to waste one third of the battery capacity.
Yes, I would like to use the OLED display as a module, and indeed, there is a 10k pull-up resistor on each of the SDA/SCL lines! However, as I was looking at the wiring of my MCU, I didn't see pull-up resistors on the i2c GPIO pins.
