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Signal Input Requirements (Teensy 4.1)

Before diving into ViewPoint, it's important to note the input signal requirements for sketches like SignalAnalyzer_A0 and LiveLissajous.

When interfacing an external signal or function generator with the Teensy 4.1 analog input, it is critical to ensure that the input signal remains within the safe operating range of the ADC.

Do not exceed the ADC input range

The Teensy 4.1 ADC operates over a 0 V to 3.3 V input range. Applying voltages outside this range can permanently damage the microcontroller.

Voltage Range Constraints

The Teensy 4.1 ADC operates over a 0 V to 3.3 V input range. Applying voltages outside this range can result in:

  • ADC clipping (invalid measurement)
  • Nonlinear distortion
  • Potential damage to the microcontroller

To safely interface a bipolar signal (e.g., a sine wave centered around 0 V), the signal must be level-shifted and amplitude-limited:

  • Maximum amplitude: < 3.3 V peak-to-peak
  • Recommended offset: 1.65 V (midpoint of the ADC range)

50 Ω Output Considerations

Many laboratory signal generators assume a 50 Ω load impedance, which affects the actual output voltage.

If the generator is set to output (for example) 3.0 Vpp into 50 Ω, but the Teensy input is high impedance, the actual voltage seen at the pin can be ~2× higher than expected.

Warning

This can easily exceed the 3.3 V limit and damage the input.

Use one of the following:

  • Enable “Hi-Z” output mode on the signal generator (if available), or
  • Use a 50 Ω feedthrough termination (BNC terminator) at the input.

This ensures the generator behaves as intended and prevents overvoltage conditions.