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Raspberry Pi health monitoring HAT adds ESP32 and battery for wearables mode

Sep 25, 2019 — by Eric Brown 4,253 views

ProtoCentral’s open source “Healthy Pi v4” HAT for vital sign monitoring advances from the v3 model with an ESP32 SoC with WiFi AP and BT-BLE and a battery for portable use including a wearable mode without a Raspberry Pi.

In 2017, Bangalore, India-based ProtoCentral launched its HealthyPi v3 HAT for the Raspberry Pi for low-cost multi-parameter patient monitoring. Now ProtoCentral has opened pre-orders on Crowd Supply for a similarly open source Healthy Pi v4 model with considerable improvements, including a switch from an Atmel ATSAMD21 Cortex-M0 MCU to a more powerful Espressif ESP32 SoC and support for a battery and standalone wearable operation.

Healthy Pi v4 HAT (left) and basic kit
(click images to enlarge)

The Healthy Pi v4, which we saw on CNXSoft, is once again billed as an affordable solution for DIY home health monitoring in emerging nations. There are still no approvals such as FDA or IEC, but the device can be used in more regulated markets for personal use or for education, research, and medical device prototyping.

The basic, $199 HAT kit features temperature, pulse oximetry, and ECG/respiration sensors, as well as 20 adhesive, single-use ECG electrodes and a three-electrode ECG “snap connector” cable. There’s also a SpO₂ finger-clip probe with a DB9 connector and a HAT mounting kit with headers and screws. New kit features include a 1000mAh LiPo battery and a Qwiic-based temperature sensor.


If you act soon, there may be a few $169 early bird packages left. After the products ship on Jan. 10, 2020, the standard $199 price will jump to $249.

Healthy Pi v4 Complete Kit (left) and detail view
(click images to enlarge)

There’s also a Healthy Pi v4 Complete Kit that sells for $349 early bird, $399 regular, and $449 retail. This adds a Raspberry Pi 3B+ SBC, as well as the official Raspberry Pi 7” touchscreen, a SmartiPi Touch case, and a 2.5A isolated, 5V/2.5A USB power adapter. A 16GB microSD card comes pre-loaded with Raspbian and the otherwise freely downloadable, HealthyPi software. There’s also a new isolated, medical-grade USB wall power adapter with plugs for US, EU, UK, and AU markets.

Espressif’s ESP32 SoC supplies much more processing power, memory, and storage than the SAMD21 MCU. It’s built on Cadence’s 32-bit Tensilica Xtensa LX6, a dual-core MCU with an 80MHz to 240MHz clock rate and 600 DMIPS performance and integrates 4MB flash and 520KB RAM.

The ESP32 also includes a 2.4GHz 802.11n radio with WiFi and Access Point (AP) mode plus dual-mode Bluetooth 4.2 BLE. Most likely, you’ll be using the HAT with a Raspberry Pi model with WiFi and Bluetooth, and if you have the RPi 3B+ or 4, you’ll get faster 802.11ac. In any case, with the new wearable mode, the onboard wireless lets you stay connected while separated from the Pi.

The wearable mode is enabled by the new PMIC and LiPo battery with onboard charging support. A physical switch swaps the modes. A new Android app lets you monitor the wearable or the combined Pi-connected device as an alternative to the previous GUI running on the Pi, which can also stream to Linux, Mac, and Windows desktops.

Healthy Pi v4 GUI (left) and Android app
(click images to enlarge)

The ESP32’s WiFi AP mode enables a webserver for streaming data or performing OTA updates. Both the BLE-connected Android app and GUI display can stream continuous readouts of ECG, respiration, and PPG data, as well as computed heart rate, respiration rate, SpO₂, and temperature readings.

As before, the 65 x 56mm HealthyPi connects to the Raspberry Pi via the UART interfaces on the 40-pin header. There’s also a USB CDC device interface and an extra UART connector for hooking up an external blood pressure module.

You can use the Arduino IDE to program the device or use the alternative, Arduino-compatible Espressif IDE. Arduino C++ helper libraries and additional examples sketches are in the works. The Java- and Raspbian-based GUI software integrates an MQTT client. Once again, the HealthyPi hardware is available with Eagle schematics, layout files, and BOM.

Further information

The HealthyPi v4 is available through Oct. 29 starting at $179 early bird or $199 standard, with shipments due Jan. 10. More information may be found on the HealthyPi v4 CrowdSupply page and more should eventually appear on the ProtoCentral website.


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