MyoWare 2.0 ENVELOPE unstable on Raspberry Pi USB (works on PC, tested with ESP32 and Arduino Uno)

Sensors Biometrics
1

Hello, I am using a MyoWare 2.0 sensor and reading the ENVELOPE output via USB serial.

When the system is connected to a PC via USB (MyoWare → ESP32/Arduino → PC), the readings are stable and correct.

However, when I connect the exact same system to a Raspberry Pi via USB (MyoWare → ESP32/Arduino → Raspberry Pi), a reading fault occurs: the Raspberry Pi does not receive the correct sensor values (the readings become unstable/saturated and the sensor LED turns on immediately).

I tested this with both ESP32 and Arduino Uno, and the same issue occurs on both boards.

2

Sounds like a ground loop or ground noise. Do you have a battery pack you could power the Pi and display from? Another option would be a USB isolator between the Pi and Arduino/ESP32. (And for safety reasons, it’s a ** really ** good idea to use an isolator anyway.)

1 Like
3

Following my previous message regarding the saturation issue with the MyoWare 2.0 sensor, I would like to provide an update.

I completely disconnected the Raspberry Pi from the system to rule it out as the cause.

I am now testing the sensor in a minimal setup:

MyoWare 2.0 → ESP32 (or Arduino Uno)

The ESP32 is powered from a dedicated external power supply (wall adapter), not from my laptop USB port.

There is no Raspberry Pi, no HDMI connection, and no additional shared ground paths.

However, the exact same issue still occurs:

  • The sensor LED turns on continuously.

  • The ENVELOPE output saturates near the maximum ADC value.

  • The signal remains high even without strong muscle contraction.

I measured the supply voltage and it is stable and within the specified operating range of the sensor.
The current consumption is normal and does not exceed the sensor’s maximum rating.

Since this behavior occurs even in a minimal setup powered from an external supply, the issue does not appear to be related to Raspberry Pi grounding, HDMI interference, or USB noise from a computer.

Could this indicate:

  • Front-end amplifier saturation?

  • REF electrode instability?

  • Improper biasing of the signal?

  • Or a possible hardware fault in the sensor?

Thank you for your assistance.