1# IoT Hardware<a name="EN-US_TOPIC_0000001117425053"></a> 2 3- [Introduction](#section11660541593) 4- [Directory Structure](#section1464106163817) 5- [Constraints](#section1718733212019) 6 7## Introduction<a name="section11660541593"></a> 8 9The Internet of Things \(IoT\) hardware subsystem provides APIs for operating IoT devices, including flash, general-purpose input/output \(GPIO\), Inter-Integrated Circuit \(I2C\), pulse width modulation \(PWM\), universal asynchronous receiver-transmitter \(UART\), and watchdog APIs. 10 11## Directory Structure<a name="section1464106163817"></a> 12 13``` 14/base/iothardware/peripheral 15├── interfaces 16 └── inner_api # APIs for operating IoT devices 17``` 18 19## Constraints<a name="section1718733212019"></a> 20 21The IoT hardware subsystem is compiled using the C language. Currently, only the Hi3861 development board is supported. If you want to use other chips, you need to implement OpenHarmony APIs. 22 23