Simple Handheld Thermal Imager

This project contains HW design files and firmware for a cheap handheld 32x24 thermal imager based on the MLX90640 sensor, forked from https://gitee.com/qlexcel/thermal-cam The most common two-button MLX90640 product available at eBay or AliExpress at the end of 2022 seems to be using a similar board design and the same FW binary from the linked repository.

Board schematics were made in Altium designer and can be viewed in the free web viewer (https://www.altium.com/viewer/). I do not have access to Altium Designer and do not need another board, so I won't be making a version for KiCad or other free tool. But feel free to open a PR if you have lots of free time on your hands. :)

My goal is simply to make the firmware a bit more polished, flexible and up to date with recently available tools.

Changes

• new features:
  • buttons now control a simple menu
    • left button selects action, right button activates it / cycles values
  • runtime selectable refresh rate
    • from 1 Hz (lower noise) up to 16 Hz (faster updates); default 8 Hz as a compromise
  • runtime selectable emissivity
    • 12 presets for common types of materials
  • runtime selectable color scales (black-body, blue-red-white, rainbow, high-contrast)
  • runtime selectable temperature ranges (automatic + 5 fixed range presets)
• fixes:
  • fixed glitches and improved accuracy at high temperatures (tested up to 600 °C)
  • improved stability of automatic range (min / max use a mild averaging)
• other changes:
  • battery indicator reworked and moved to the left to make space for action selector
  • voltage considered "full" changed from 4.2 V to 3.8 V (Li-ion drops off fast, despite still being almost full)
• code rework:
  • sources cleaned up a bit and converted to UTF-8
  • reduced code size to fit all features under the linker limit of Keil v5 MDK non-commercial version
  • new drawing function (more maintainable and flexible)
  • performance optimizations (maximum achievable refresh rate increased from ~5.5 Hz to 16 Hz)

Known issues

• BPM saving is broken (files contain only blue color or are otherwise incomplete)
• emissivity values 1.00 and 0.04 are displayed incorrectly
• stuck at black screen after activating USB mode when USB is not connected

Long term plans

• support a newer compiler (or better, a FOSS toolchain, to get rid of the 32k limitation)
• translate, add, and improve comments

How to build and use

• get and install MDK-ARM 5.38a or similar version (https://www.keil.com/demo/eval/arm.htm)
• get and install the legacy Arm Compiler 5 (https://developer.arm.com/downloads/view/ACOMP5)
  • if you get a weird file access error during instalation, run the .msi installer from data/ folder directly
  • make sure you install it to the MDK location (e.g. Keil\_v5/ARM/ARM_Compiler_5.06u7/), otherwise you will get licensing errors
• open Keil uVision 5, install support package for GD32F103C8T6 and open the the ThermalCam project
• in Project → Manage → Project items..., add the ARM Compiler 5 to Folders/Extensions as another compiler
• build the project (F7)
• connect ST-Link programmer to the board
• use ST-Link Utility to back up the original firmware (in case your seller made changes you wish to keep)
• back in Keil uVision, you can now load the program to your board (F8)

DISCLAIMER: These instructions may be outdated and may not work, may brick your device, and / or may open a gate to Hell or whatever if you don't know what you are doing. You know the drill.

Original description in Chinese

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ThermalCam--红外热成像仪

视频介绍： https://www.bilibili.com/video/BV1634y1d7Ly/

0. 关于本项目

基于MLX90640传感器制作的红外热成像仪。

成本两百多，易于制作。

再也不用手感应测温了，被芯片烫伤、被高压电过的硬件狗飘过~~

1. 物料说明

MLX90640：分辨率为24x32的红外探头，如果只是测温，不想看像素级的温度已经足够。毕竟还有人用8x8分辨率的AMG8833。注意MLX90640 有两个型号， A 型和 B 型，型号全称为：MLX90640ESF_BAA/BAB。

一定要选择B型。具体区别可以去看我的博客。

屏幕：3.2寸，240x320分辨率。因为不同公司生成的屏幕引脚并不一定兼容，大伙们购买的时候要对清楚。我这里使用的是深圳艾斯迪科技的LCDT3213440AL。购买链接。买不带触摸屏的，我直接买的时候30块，现在......今年的电子行情懂的都懂......

MCU：使用GD32F103C8T6，不可以使用STM32F103C8T6。因为STM主频72M，GD主频108M，差了50%，就是这50%会导致视频显示特别卡，程序里面能优化的地方都优化了，C8T6的RAM只有20K，实际使用远远不够，因此程序里面很多变量做了共用存储空间处理，如果哪位大佬有兴趣可以继续优化下，或者直接上GD32F103CBT6。

SPI FLASH：使用的国产XT25F128BSSIGU，可以替换为华邦的或GD的，程序应该是兼容的。当然容量大小也可以更改。

外壳：外壳推荐在TB上买现成的来加工，规格为90x70x28，价格2元。购买链接。加工的话需要美工刀和手钻。

锂电池：我使用的是65mmx30mmx7mm，容量1800毫安的电池。电池可以使用更大的，因为外壳内部空间还有很大。