Using Basys 3 and DHT11 Temperature & Humidity Sensor By Hanuman Mattupalli
This project presents an FPGA-based integrated system that combines a 12-hour digital clock with DHT11 environmental sensing, implemented on the Basys 3 development board. The system features dynamic display multiplexing, adaptive sensor polling, and context-aware controls, all while maintaining efficient hardware utilization. It demonstrates: Accurate timekeeping (±1 sec/day), Reliable sensor measurements (±2°C, ±5% RH), Compact integration using <15% of FPGA resources. This design is fully validated through hardware testing and real-time performance.
Basys3 has some convincing Features which made me use it this project particularly. Those features include:
Seven Segment Displays: Displaying Real-time adjustable clock requires some Display interface, which Basys3 has it inbuilt. Other FPGA's can also be used but we have to connct 2 Pmod Seven segment displays additionally.
Pmod Ports: Basys 3 has 4 Pmod connectors (JA–JD). Each Pmod interface has 8 data lines and 2 power lines (3.3V and GND). Interfacing DHT11 sensor can be done using these Pmod ports.
The DHT11 is a low-cost, digital temperature and humidity sensor. Measures: -Humidity: 20–90% RH (±5%) -Temperature: 0–50°C (±2°C) -Supply Voltage: 3.3V to 5V -Interface: Single-wire digital protocol (not I²C or UART!) -Output: 40-bit digital data (in 5 bytes) -Sampling Rate: 1 Hz (1 reading per second)
Bits: 39 – 32 Humidity integer part e.g., 00110111 → 55% RH 31 – 24 Humidity decimal part Always 0 for DHT11 23 – 16 Temperature integer part e.g., 00011000 → 24°C 15 – 8 Temperature decimal part Always 0 for DHT11 7 – 0 Checksum Sum of the first 4 bytes modulo 256
Sensor limitation: Only 1 reading per second allowed, Timing is critical: Data bits are identified by pulse lengths: Logic '0': 50 µs low + 26–28 µs high Logic '1': 50 µs low + 70 µs high
All these constraints are carefully checked and implemented in DHT11_read file.
Digital_clock reference: https://youtu.be/3Waa9Y4OcLo?si=B7p25YSnFnwkum51
Basys 3 Device Part (for Vivado): If the board is not listed, search using the part number: xc7a35tcpg236-1