dankamongmen/nau7802

readme

An [esp-idf](https://github.com/espressif/esp-idf) component for interfacing
with the [NAU7802](https://www.nuvoton.com/export/resource-files/en-us--DS_NAU7802_DataSheet_EN_Rev2.6.pdf)
24-bit ADC, especially as packaged on e.g. the
[Adafruit NAU7802](https://www.adafruit.com/product/4538) and
[SparkFun Qwiic Scale](https://www.sparkfun.com/products/15242). This is
similar to the [HX711](https://www.digikey.com/htmldatasheets/production/1836471/0/0/1/hx711.html),
and usually used for working with load cells.

The NAU7802 is available as a discrete component in both
[KGI](https://www.nuvoton.com/products/smart-home-audio/audio-converters/precision-adc-series/nau7802kgi)
(PDIP16L through-hole) and
[SGI](https://www.nuvoton.com/products/smart-home-audio/audio-converters/precision-adc-series/nau7802sgi/)
(16L SOP SMD) form factors.
It operates over I²C. It can accept between 2.7V and 5.5V, and operates
between -40C and 85C.

This is present in the [Component Registry](https://components.espressif.com/)
as [dankamongmen/nau7802](https://components.espressif.com/components/dankamongmen/nau7802).

[![Component Registry](https://components.espressif.com/components/dankamongmen/nau7802/badge.svg)](https://components.espressif.com/components/dankamongmen/nau7802)

## Using the NAU7802

The NAU7802 exposes an I²C-compatible wire interface.

### Channels

The NAU7802 presents two channels, but switching between them is an expensive
operation (including an internal calibration). The channels have different
input capacitance. If you only need one channel, a capacitor to ground can tie
together Vin2N and Vin2P to eliminate some noise; suggested values are 330pF
for 3.3V AVDD and 680pF for 4.5V AVDD. If this is done, be sure to call
`nau7802_set_pga_cap(i2ch, true)`.

### Power

The NAU7802 can accept between 2.7V and 5.5V for its digital input DVDD. It
should generally be the same power source as your MCU (e.g. 3.3V for ESP32).
AVDD powers the analog components, and must not exceed DVDD. It can either
come from an external power source, or be converted from DVDD using an
internal LDO. By default, the NAU7802 expects a voltage on AVDD. To instead
use the LDO, call `nau7802_enable_ldo()` with the greatest `nau7802_ldo_level`
*less than* your DVDD (e.g. `NAU7802_LDO_30V` when powered by a 3.3V DVDD).
`pga_ldomode` sets the `LDOMODE` bit of the `PGA` register, allowing use
of a higher ESR capacitor…but I'm not quite sure what capacitor it refers to.