Embedded Linux - TMP102 websocket server

This project demonstrates a simple IoT solution using the BeagleBone Black (BBB) to monitor temperature in real-time via a web interface. A TMP102 sensor measures temperature, while a lightweight web server displays the readings on any connected device.

Key Features:

• Real-time temperature monitoring via a web browser

• Minimal Linux setup with custom kernel and BusyBox

• Network boot (NFS) for easy development

• Lightweight WebSocket server for live updates

• Low-power & embedded-friendly design

Ideal for learning embedded Linux, device drivers, and IoT prototyping.

Prerequisites

• BeagleBone Black board

• Host machine running Linux (Ubuntu/Debian recommended)

• MicroSD card (4GB+) with FAT32 partition and BOOT flag is set.

• TMP102 temperature sensor connected to BBB's I2C-2 bus

• Network connection between BBB and host machine

Setup Overview

1. Cross-Toolchain Setup

2. U-Boot Compilation

3. Linux Kernel with TMP102 Driver

4. BusyBox Root Filesystem

5. NFS Boot Configuration

6. Device Tree Modification for I2C-2

7. WebSocket Server Setup

Building a Cross-Compiling Toolchain

1. Install Dependencies: Use apt-get to install tools like build-essential, git, and autoconf.

2. Download Crosstool-NG: Clone the repository, checkout a stable version (e.g., crosstool-ng-1.26.0), and bootstrap it.

3. Configure & Build: Run ./configure --enable-local, then make to compile. Use ./ct-ng menuconfig to set ARM Cortex-A8 target, Musl C library, and GCC 13.2.0.

4. Generate Toolchain: Execute ./ct-ng build to produce the toolchain in ~/x-tools/.

Setting Up U-Boot for BBB

1. Download U-Boot: Clone the U-Boot repository and checkout a stable tag (e.g., v2024.04).

2. Configure & Compile: Use make am335x_evm_defconfig, then compile with make DEVICE_TREE=am335x-boneblack.

3. Prepare SD Card: Create a FAT32 partition with BOOT flag, copy MLO and u-boot.img to it.

4. Configure Environment variables

Linux Kernel Driver for TMP102 Temperature Sensor

Kernel config option: CONFIG_TMP102=y ,usually found under "Hardware Monitoring". Also, Ensure that your kernel supports booting the system using a root filesystem mounted over NFS.

BusyBox Root Filesystem

In the BusyBox configuration interface, set the installation directory for BusyBox to the export path of NFS.

NFS Boot Configuration

to boot from NFS from the host machine.
=> printenv bootargs // bootargs=console=ttyO0,115200n8 debuge earlyprintk root=/dev/nfs ip=192.168.0.100:::::eth0 nfsroot=192.168.0.101:/home/temp/fs,nfsvers=3,tcp rw // 192.168.0.101 is the local IP address for the host, change it according to your setup. /home/temp/fs is the NFS export path for the host.

Device Tree Modification for I2C-2

We've used I2C-2 to connect the tmp102 to BBB and we need to let the kernel know about it so we

Create a Device Tree Overlay

/dts-v1/; 
/plugin/;

/ {
    fragment@0 {
        target = <&i2c2>;
        __overlay__ {
            #address-cells = <1>;
            #size-cells = <0>;
            tmp102@48 {
                compatible = "ti,tmp102";
                reg = <0x48>; //TMP i2c addr
            };
        };
    }; 
};

Compile the Overlay

dtc -@ -O dtb -o BB-I2C2-TMP102.dtbo -b 0 BB-I2C2-TMP102.dts

edit U-Boot environment variable bootargs

Load kernel, DTB, and overlay from MMC, merges them, and boots. =>printenv bootcmd bootcmd=load mmc 0:1 ${loadaddr} zImage; load mmc 0:1 ${fdtaddr} am335x-boneblack.dtb; load mmc 0:1 ${overlayaddr} BB-I2C1-TMP102.dtbo; fdt addr ${fdtaddr}; fdt resize 8192; fdt apply ${overlayaddr}; bootz ${loadaddr} - ${fdtaddr}

WebSocket Server Setup

Use your cross-compiling toolchain and compile server.c, ensure that mongoos.h and mongoos.c are in the same folder.

arm-training-linux-musleabihf-gcc server.c mongoose.c -o server -I. -static

put the compiled server into your NFS and run it ./server P.s : change the *s_http_addr = "http://192.168.0.100:8000"; with your BBB LAN IP

Finally enter the BBB IP with the the server port into your browser (the pc should be on the same network LAN)

License

This code is provided AS IS without warranty. Feel free to use and modify it for any purpose.

Author

Karam Dali - Damascus (21/04/2025)