LightTAM_RFID_Reader/README.md

LightTAM RFID Reader

This is firmware for an RFID reader for the LightTAM software. The LightTAM repository is here. The LightTAM RFID Reader is built using an STM32F103C8 controller (mainly sold on BluePill boards), a PN532 RFID reader, and an HD44780 LCD display for the I2C bus. MCU is programmed using STM32Cube with CMake and HAL libraries. For editing (or debugging), I recommend using VS Code with STM32Cube extension installed.

This program utilizes libraries from these repositories:

• STM32_HAL_I2C_HD44780
• pn532-lib

Hardware Connection

• PN532 RFID Reader: Connected via UART or I2C (depending on configuration).
• HD44780 LCD Display: Connected via I2C using a PCF8574 I/O expander.
• Three LEDs: Connected to PB12 (red), PB13 (yellow), and PB14 (green).
• Power Supply: 5V input, regulated to 3.3V for the STM32 and peripherals.

Wiring

Device	STM32 Pin	Notes
PN532 (I2C)	PB6 (SCL)	I2C1 SCL
	PB7 (SDA)	I2C1 SDA
LCD (I2C)	PB6 (SCL)	Shared I2C bus
	PB7 (SDA)	Shared I2C bus
LED Red	PB12
LED Yellow	PB13
LED Green	PB14
Computer (RXD)	A2	USART2 TX
Computer (TXD)	A3	USART2 RX
Debug (RXD)	PA9	USART1 TX
Debug (TXD)	PA10	USART1 TX

Firmware Operation

After startup, the firmware initializes all peripherals: I2C, GPIOs, the LCD display, and the PN532 RFID reader. The main loop performs the following steps:

1. Idle State:

   • The green LED (PB14) is ON, indicating the system is ready to scan for RFID tags.
   • The LCD displays a welcome or ready message.

2. RFID Scanning:

   • The firmware continuously polls the PN532 for the presence of an RFID tag.

3. Tag Detection:

   • When a tag is detected, the UID is read.
   • The yellow LED (PB13) briefly turns ON to indicate a tag is being processed.
   • The LCD displays the UID or relevant information.

4. Tag Validation:

   • The firmware checks if the tag UID is valid (e.g., against a list or via communication with the host).
   • If the tag is valid, the green LED (PB14) blinks or stays ON.
   • If the tag is invalid, the red LED (PB12) turns ON to indicate an error or unauthorized tag.

5. Status Indication:

   • The LEDs provide immediate feedback:
     • Green (PB14): System ready or access granted.
     • Yellow (PB13): Tag detected and being processed.
     • Red (PB12): Error or access denied.

6. Communication:

   • The firmware can send the UID or status to a host system via UART or another interface if required.

7. Return to Idle:

   • After processing, the system returns to the idle state, with the green LED ON and others OFF.

All logic is implemented using STM32Cube HAL libraries. The code is organized under the Core/ and Drivers/ directories.