The Adafruit ADS7128 8-Channel ADC and GPIO Expander is a bit of a Platypus of the I2C expander world: hard to categorize as just an ADC or a GPIO expander since it combines the capabilities of both with great capabilites! Usually, you only get ADC or I/O so it's nice to see this combo product.

Featuring the aforementioned ADS7128, it can run on 3.3 or 5V logic and power, and all 8 I/O pins can individually configured to perform either 12-bit SAR analog input, push-pull or open drain digital output, or digital input. This makes it great as a general-purpose glue chip when you want to add more pins or analog/open-drain outputs to a microcontroller or microcomputer.

The ADS7128 also has a lot of fancy extras that make it a good ADC companion even if your main core already has analog inputs. It can run in standalone mode with zero-crossing detection or RMS computation. Not only can it count and track threshold crossings, but it also has an alert trigger output. 

Unlike many ADC/expanders, it has two power supplies: the DVDD digital supply and AVDD analog supply are separate so you can use 3V logic for the digital I/O and I2C communications while the analog inputs and digital outputs can be as high as 5V. Or vice versa!

Interfacing is easy - this sensor uses plain, universal I2C. We put this sensor on a breakout board with all the extras needed so you can use it with 3.3V or 5V power/logic microcontrollers. We have written libraries for Arduino (C/C++) as well as CircuitPython (Python 3) so you can use this sensor with just about any kind of device, even a Raspberry Pi!

As if that weren't enough, we've also added SparkFun qwiic compatible STEMMA QT connectors for the I2C bus so you don't even need to solder. Just wire up to your favorite micro with a plug-and-play cable to get analog inputs and digital I/Os ASAP. For a no-solder experience, just wire up to your favorite micro, like the ESP32 V2  Feather using a STEMMA QT adapter cable. The Stemma QT connectors also mean the ADS7128 can be used with our various associated accessories. QT Cable is not included, but we have a variety in the shop.

Technical Details:

ADS7128 Specifications

• Datasheet & Product Information
• 8 channels configurable as any combination of:
• Up to 8 analog inputs, digital inputs, or digital outputs
• GPIOs for I/O expansion:
• Open-drain, push-pull digital outputs
• Analog watchdog:
• Programmable thresholds per channel
• Event counter for transient rejection
• Wide operating ranges:
• AVDD: 2.35 V to 5.5 V
• DVDD: 1.65 V to 5.5 V
• -40°C to +85°C temperature range
• CRC for read/write operations:
• CRC on data read/write
• CRC on power-up configuration
• I2C interface:
• Up to 3.4 MHz (high-speed mode)
• 8 configurable I2C addresses
• Programmable averaging filters
• Root-mean-square module:
• 16-bit true RMS output
• Programmable RMS time window
• Zero-crossing-detect module:
• ZCD output corresponding to any analog input
• Built-in transient rejection and hysteresis
• Digitally adjustable detection threshold
• Product Dimensions: 30.5mm x 17.8mm x 4.7mm / 1.2" x 0.7" x 0.2"
• Product Weight: 2.1g / 0.1oz

Package Includes:

• 1 x Adafruit 6494 ADS7128 8-Channel ADC and GPIO Expander - STEMMA QT / Qwiic