task_read_camera.cpp File Reference

Thermal camera reading and hot blob detection task. More...

#include "PrintStream.h"
#include "task_read_camera.h"
#include <Arduino.h>
#include <Wire.h>
#include "shares.h"
#include "task_webserver.h"
#include "adafruit_mlx90640.h"

Macros
#define	HOTBLOB_DETECT_THRESHOLD   50.0f
#define	HOTBLOB_INCLUSION_THRESHOLD   49.0f
#define	FIRE_ALERT_THRESHOLD   70.0f
#define	FIRE_COOLDOWN_THRESHOLD   60.0f
#define	NUM_PIXELS   768

Functions
void	findHotBlob (const float *frame, uint16_t seedIdx, float tempThreshold, uint16_t &outCentroidIdx, float &outMaxTemp, float &outAvgTemp, uint16_t &outSize, float &outCentroidX, float &outCentroidY)
	function which finds the centroid of a hot blob in a thermal frame
void	task_read_camera (void *p_params)
	task which reads the MLX90640 thermal camera and detects hotspots

Variables
Adafruit_MLX90640	mlx

Detailed Description

Thermal camera reading and hot blob detection task.

Author

Jackson Cordova, GPT5-mini

Date

November 2025

Function Documentation

findHotBlob()

void findHotBlob	(	const float *	frame,
		uint16_t	seedIdx,
		float	tempThreshold,
		uint16_t &	outCentroidIdx,
		float &	outMaxTemp,
		float &	outAvgTemp,
		uint16_t &	outSize,
		float &	outCentroidX,
		float &	outCentroidY )

function which finds the centroid of a hot blob in a thermal frame

this functions performs a breadth-first search (BFS) starting from a seed pixel to find all connected pixels above a temperature threshold, effectively identifying a "blob" of hot pixels. It computes the weighted centroid of the blob based on pixel temperatures, as well as the maximum temperature, average temperature, and size of the blob.

Parameters

frame	pointer to the thermal frame array (size 768)
seedIdx	index of the seed pixel to start the search from
tempThreshold	temperature threshold for including pixels in the blob
outCentroidIdx	reference to store the index of the computed centroid pixel
outMaxTemp	reference to store the maximum temperature found in the blob
outAvgTemp	reference to store the average temperature of the blob
outSize	reference to store the size (number of pixels) of the blob
outCentroidX	reference to store the X coordinate of the centroid
outCentroidY	reference to store the Y coordinate of the centroid

task_read_camera()

void task_read_camera

(

void *

p_params

)

task which reads the MLX90640 thermal camera and detects hotspots

This task continuously reads frames from the MLX90640 thermal camera at a set refresh rate. It processes each frame to find the hottest pixel and then identifies a connected "hot blob" of pixels around it that exceed a defined temperature threshold. The task computes the centroid of the hot blob and applies temporal smoothing to reduce jitter in the detected position. If the maximum temperature of the blob exceeds a fire alert threshold, it sets a shared boolean "fire" to true. The task runs indefinitely with no delay, relying on the camera's refresh rate for timing.

Parameters

p_params

not used and should be set to void in the xTaskCreate call