# External ADC
If you're running out of analog inputs, or just want more accurate analog readouts, you can add external ADCs.
An ADC (analog to digital converter) measures voltage and turns it into a value. It is required to make sense if data from sensors and potentiometers, and is used widely in consumer electronics for microphones, cameras, meassuring tools, etc. Anything that takes something *physical,* like a distance/temperature/weight/brightness*,* and turns it into a value for the computer to use, needs an ADC. Needless to say, any microcontroller should have an ADC - and they have. The analog inputs on a Pro Micro or Pico board sends the signal to the ADC. Typically, the ADCs that are built into the microcontroller chips are noisy and inaccurate. However, fairly quick and usually more and good enough for controller purposes.
Think about it; how tall are you? You could say you're 181.5 cm tall, but that is not accurate. With a better measuring tool you could find out that you're 1.8178 meters tall. With an even better tool you get 1.81776342235 meters. However, you'll never get 100% accuracy, you can never get an *exact* measurement. This is the trade-off with ADCs. The accuracy is measured in bits. A 10-bit ADS can describe the range of 0 - 5 volts in 1023 steps. A 16-bit ADC has 65 536 steps, which will make it more accurate. However, it will also be more expensive and slower. So what do you need? Accuracy? Speed? Cheap? High-end?
## Supported ADCs
### ADS1115
* 16-bit
* 4 inputs
* I2C
* Fairly slow, but fast enough for joystick controller purposes.
This is a popular chip, and its selling point is its accuracy - with 16-bit resolution and a stable onboard referance voltage. Fairly quick for being 16-bit, but mega slow compared to 10-12-bit ADCs. High in stock on JLCPCB and relatively inexpensive. It has 4 channels and connects via I2C, so it will need 2 pins from the microcontroller. More on this under [wiring.](/ddc/2.-wiring/analog/external-adc.md) You can add up to 4 of these for 16 additional analog inputs.
A big effort has gone into optimizing the readouts from this ADC. The existing, popular libraries for this IC are extremely slow and memory heavy - making them not suited for DDC. Instead I've made my own algorithms, which are a lot more efficient in both processing and memory usage.
### HX711
Dedicated strain gauge load cell amplifier and 24-bit ADC, covered under the load cell chapters in this manual.
---
# Agent Instructions: Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.
Perform an HTTP GET request on the current page URL with the `ask` query parameter:
```
GET https://dahl-design.gitbook.io/ddc/1.-project-planning/analog-inputs/external-adc.md?ask=
```
The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.
Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.