Schematics

The hardware for the system include the Adafruit PN532 Breakout Board, Nucleo Microcontroller, Upduino ICE40 FPGA, and a speaker with an audio amplifier. The audio amplifier (a TI LM386) is in place to allow the speaker to draw more current than the FPGA pin would allow. The audio amplifier circuit comes from the LM386 datasheet.1

wiring

Schematic of RFID Doorbell System.

Source Code Overview

The code base for this project is broken into three sections:

  • MCU code, written in C
  • FPGA code, written in SystemVerilog
  • FPGA testbenches, also written in SystemVerilog

The source code for the project is located in the Github repository here.

MCU Code

Our microcontroller code includes multiple library files, using the CMCIS structures, and a main.c file in which all of the library files are included. The library files are named STM32L432KC_x.c where x is the name of the peripheral driven by that library. For example, the I2C is used to communicate with the PN532 RFID/NCF Controller. The I2C driver is named STM32L432KC_I2C.c.

The main.c file calls functions from the various libraries and allows the MCU to act as the controller for both I2C (to the PN532) and SPI (to the FPGA).

For more information see the design page.

FPGA Code

The code to program the FPGA resides in one SystemVerilog file titled main.sv. The first module in this file, top, controls the FGPA and calls the other modules as needed.

The module entitled tune is the main finite state machine (FSM) for the FPGA. Below is the full netlist (all of the connections between modules) on the FPGA.

netlist

FPGA Netlist.

For more information see the design page.

FPGA Testbenches

A series of testbenches were created to test the FPGA prior to the integration with the MCU.

These testbenches are listed as follows:

  • SPI
  • Main FSM (the tune module)
  • Frequency generator
  • Duration counter
  • Decomposition of the MCU output
  • Enables for the system
  • Top module

Bill of Materials

Item Purpose Part Number Quantity Unit Price Vendor/Source
Adafruit PN532 NFC/RFID Controller / breakout board RFID peripheral 364 1 $39.95 Adafruit
Nucleo STM32L432KC Microcontroller Interface between RFID peripheral and FPGA, runs algorithm to determine doorbell NUCLEO-L432KC 1   Lab kit
Upduino ICE40 & UP5K FPGA Creates PWM signal to drive speaker based on RFID ID# N/A 1   Lab kit
8Ω speaker Doorbell output speaker N/A 1   Stock room
Resistor, 4.7kΩ Pull-up resistor for I2C connections N/A 2   Stock room
Resistor, 15kΩ Speaker volume control N/A 1   Stock room
Resistor, 2.7kΩ Speaker volume control N/A 1   Stock room
LM386 Audio amplifier Audio amplifier LM386N-4/NOPB 1   Stock room
Slide switch On/off switch for doorbell speaker N/A 1   Stock room
Wire, various length Connection between electronics N/A variable   Stock room

Total cost: $39.95

  1. ​​“LM386 Low Voltage Audio Power Amplifier Datasheet.” Texas Instruments, May 2017. [Online]. Available: https://www.ti.com/lit/ds/symlink/lm386.pdf. ↩