Thermal camera on an Arduino Uno

// Thermal camera: an AMG8833 Grid-EYE and an ST7735 color screen.
//
//   SDA, SCL       the AMG8833 (address 0x69), VIN and GND from the rails
//   pins 10, 9, 8  the screen's CS, A0 (DC) and RESET
//   pins 11, 13    the screen's SDA (MOSI) and SCK; VCC and LED from the rails
//
// The Grid-EYE gives sixty-four temperatures ten times a second. Each one is
// painted as a 16x16 square, eight across and eight down, in a thermal
// palette from blue at 20 C through red to yellow at 36 C and over, so a
// hand stands out against a room. The hottest pixel's temperature is written
// under the picture.
//
// The screen is driven a pixel at a time over the pins, so a frame takes a
// while; the sketch only repaints the squares whose color changed.

#include <Wire.h>
#include <SPI.h>
#include <Adafruit_GFX.h>
#include <Adafruit_ST7735.h>
#include <Adafruit_AMG88xx.h>

Adafruit_ST7735 tft(10, 9, 8);
Adafruit_AMG88xx amg;

float pixels[AMG88xx_PIXEL_ARRAY_SIZE];
uint16_t shown[AMG88xx_PIXEL_ARRAY_SIZE];
int lastHot = -1000;

// 20 C to 36 C onto blue, purple, red, orange, yellow.
uint16_t colorFor(float c) {
  int t = (int)((c - 20.0) * 16.0); // 0..256 over 16 degrees
  if (t < 0) t = 0;
  if (t > 255) t = 255;
  uint8_t r, g, b;
  if (t < 64) {
    r = (uint8_t)(t * 2); g = 0; b = (uint8_t)(128 + t);
  } else if (t < 128) {
    r = (uint8_t)(128 + (t - 64) * 2); g = 0; b = (uint8_t)(192 - (t - 64) * 3);
  } else if (t < 192) {
    r = 255; g = (uint8_t)((t - 128) * 2); b = 0;
  } else {
    r = 255; g = (uint8_t)(128 + (t - 192) * 2); b = (uint8_t)((t - 192) * 3);
  }
  return tft.color565(r, g, b);
}

void setup() {
  Serial.begin(115200);
  Serial.println("Mokxi Arduino Uno: thermal camera");
  tft.initR(INITR_BLACKTAB);
  tft.fillScreen(ST77XX_BLACK);
  if (!amg.begin()) {
    Serial.println("no AMG8833: check SDA, SCL and power");
    while (1) delay(10);
  }
  for (int i = 0; i < AMG88xx_PIXEL_ARRAY_SIZE; i++) shown[i] = 0xFFFF;
  delay(100);
}

void loop() {
  amg.readPixels(pixels);
  float hottest = pixels[0];
  int where = 0;
  for (int i = 0; i < AMG88xx_PIXEL_ARRAY_SIZE; i++) {
    if (pixels[i] > hottest) {
      hottest = pixels[i];
      where = i;
    }
    uint16_t color = colorFor(pixels[i]);
    if (color != shown[i]) {
      shown[i] = color;
      tft.fillRect((i % 8) * 16, (i / 8) * 16, 16, 16, color);
    }
  }
  int hot = (int)(hottest * 10.0 + 0.5);
  if (hot != lastHot) {
    lastHot = hot;
    tft.fillRect(0, 132, 128, 16, ST77XX_BLACK);
    tft.setCursor(4, 134);
    tft.setTextColor(ST77XX_WHITE);
    tft.setTextSize(1);
    tft.print("hottest ");
    tft.print(hot / 10);
    tft.print('.');
    tft.print(hot % 10);
    tft.print(" C");
    Serial.print("hottest ");
    Serial.print(hot / 10);
    Serial.print('.');
    Serial.print(hot % 10);
    Serial.print(" C at row ");
    Serial.print(where / 8);
    Serial.print(", column ");
    Serial.println(where % 8);
  }
  delay(100);
}