How to Use USB FIFO Controller: Examples, Pinouts, and Specs

The FT245RL, manufactured by FTDI Chip, is a USB FIFO (First In, First Out) Controller designed to facilitate seamless data transfer between USB devices and a host system. It provides a simple and efficient interface for high-speed communication, making it ideal for applications requiring reliable data buffering and transfer.

• USB-to-parallel data transfer
• Embedded systems requiring USB connectivity
• Data acquisition systems
• USB-based communication in industrial automation
• Prototyping and development of USB-enabled devices

The FT245RL is a versatile and robust component with the following key technical details:

The FT245RL comes in a 28-pin SSOP package. Below is the pin configuration and description:

The FT245RL is straightforward to use in a circuit, thanks to its USB FIFO interface. Below are the steps and considerations for using the component effectively:

1. Power Supply: Connect the VCC pin to a 5V power source and the GND pin to ground. Use the 3V3OUT pin to power external 3.3V components if needed.
2. USB Connection: Connect the USBDP and USBDM pins to the USB D+ and D- lines, respectively. Ensure proper USB termination resistors are used.
3. Data Bus: Use the D0-D7 pins for parallel data transfer. These pins can be connected to a microcontroller or other digital logic.
4. Control Signals:
   • Use the RXF# pin to check if data is available in the FIFO.
   • Use the TXE# pin to check if the FIFO is ready to accept data.
   • Use the RD# and WR pins to read from and write to the FIFO, respectively.
5. EEPROM Configuration: If required, connect an external EEPROM to the EECS, EESK, and EEDATA pins for custom configurations.

• Crystal Oscillator: Use a 12 MHz crystal oscillator connected to the OSCI and OSCO pins for proper USB operation.
• Pull-Up Resistors: Ensure proper pull-up resistors are used on the USB D+ line for USB compliance.
• Decoupling Capacitors: Place decoupling capacitors close to the VCC and GND pins to reduce noise.
• Reset Pin: Tie the RESET# pin to VCC through a pull-up resistor if not used.

The FT245RL can be interfaced with an Arduino UNO for USB communication. Below is an example Arduino sketch:

// Example: Reading data from FT245RL FIFO using Arduino UNO

#define RXF 2  // Pin connected to RXF# of FT245RL
#define RD  3  // Pin connected to RD# of FT245RL
#define D0  4  // Pin connected to D0 of FT245RL
#define D1  5  // Pin connected to D1 of FT245RL
#define D2  6  // Pin connected to D2 of FT245RL
#define D3  7  // Pin connected to D3 of FT245RL

void setup() {
  pinMode(RXF, INPUT);  // RXF# is an output from FT245RL
  pinMode(RD, OUTPUT);  // RD# is an input to FT245RL
  pinMode(D0, INPUT);   // Data bus pins are inputs to Arduino
  pinMode(D1, INPUT);
  pinMode(D2, INPUT);
  pinMode(D3, INPUT);

  digitalWrite(RD, HIGH);  // Set RD# high initially
  Serial.begin(9600);      // Initialize serial communication
}

void loop() {
  if (digitalRead(RXF) == LOW) {  // Check if data is available
    digitalWrite(RD, LOW);        // Assert RD# to read data

    // Read 4 bits of data from the FIFO
    int data = (digitalRead(D3) << 3) | (digitalRead(D2) << 2) |
               (digitalRead(D1) << 1) | digitalRead(D0);

    digitalWrite(RD, HIGH);       // De-assert RD# after reading
    Serial.println(data, HEX);    // Print the data in hexadecimal
  }
}

1. Device Not Recognized by USB Host:

   • Ensure proper USB D+ and D- connections.
   • Verify that the crystal oscillator is functioning correctly.
   • Check for proper pull-up resistors on the USB D+ line.

2. No Data Transfer:

   • Verify the RXF# and TXE# signals to ensure proper FIFO operation.
   • Check the RD# and WR signals for correct timing.

3. Erratic Behavior:

   • Ensure decoupling capacitors are placed close to the power pins.
   • Verify that the RESET# pin is properly connected.

Q: Can the FT245RL operate at 3.3V?
A: The FT245RL requires a 5V power supply but provides a 3.3V output for I/O operations.

Q: Is an external EEPROM mandatory?
A: No, the FT245RL has an internal EEPROM for basic configurations. An external EEPROM is optional for custom settings.

Q: What is the maximum data transfer rate?
A: The FT245RL supports USB 2.0 Full-Speed, with a maximum transfer rate of 1 MByte/s.