README.md

AMG8833 Interpolating Camera

The 8x8 resolution of the AMG8833 produces a "blocky" display. The illusion of higher resolution may be achieved using bicubic interpolation. This is computationally intensive. On a Pyboard 1.1 the frame rate for 32x32 pixels using Python code is ~1Hz. This can be increased to ~2.5Hz using assembler.

Main README

1. Files

• cam_interp.py 32x32 pixel demo using the Adafruit 0.96 inch OLED.
• interpolate.py Portable interpolator using optimised Python code.
• interpolate_a.py Version using Arm Thumb2 Assembler.

Both versions of the interpolator provide implementations of the Interpolator class.

2. Interpolator class

Constructor:
This takes a single arg, an AMG88XX instance.

Methods:

• refresh No args. Causes the AMG88XX instance and the interpolator to update with physical data.
• __call__ args r, c. The interpolator's coordinate space covers the range 0.0 <= r <= 1.0, 0.0 <= c <= 1.0. Function call syntax causes the interpolator to return the temperature value for that row, col location.

Usage

Converting a working 8x8 camera application to use interpolation is simple. The aim is to replace the 8x8 array of pixels with a larger array of smaller pixels: the cam_interp.py demo uses 32x32 squares of size 2x2.

After instantiating the sensor, create an Interpolator:

i2c = machine.I2C(1)
sensor = AMG88XX(i2c)
sensor.ma_mode(True)  # Moving average mode
interpolator = Interpolator(sensor)

Replace

    sensor.refresh()  # Acquire data

with

   interpolator.refresh()

The iterator now needs to iterate through the number of virtual rows and cols and display smaller squares. Instead of accessing the sensor, the value is retrieved with

val = interpolator(r/max_row, c/max_col)  # Values range 0.0..1.0

Algorithm

The theory of cubic and bicubic interpolation is straightforward. This ref provides a good explanation, with Java and C++ implementations.