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 acts as a bridge, managing data flow efficiently by temporarily storing data in a queue. This component is widely used in applications requiring USB connectivity, such as embedded systems, data acquisition, and USB-to-parallel interfaces.

• USB-to-parallel data transfer
• Embedded systems requiring USB communication
• Data acquisition systems
• USB-based debugging tools
• Industrial automation and control systems

The FT245RL is a high-performance USB FIFO controller with the following key specifications:

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

1. Power Supply: Connect the VCC pin to a 3.3V power source and the VCCIO pin to either 3.3V or 5V, depending on the desired I/O voltage level. Ensure all GND pins are connected to the ground plane.
2. USB Connection: Connect the USBDP and USBDM pins to the USB D+ and D- lines, respectively. Use a USB connector for interfacing with the host system.
3. FIFO Interface: Use the D0-D7 pins for data transfer. Control the data flow using the RD#, WR, RXF#, and TXE# pins.
4. EEPROM Configuration: The integrated EEPROM can be programmed to customize USB descriptors, such as Vendor ID (VID), Product ID (PID), and device strings.
5. Clock Output: The CLKOUT pin provides a 12 MHz clock signal, which can be used to synchronize external components.

• Pull-Up Resistors: Ensure proper pull-up resistors are used on the USB D+ line for USB compliance.
• Decoupling Capacitors: Place decoupling capacitors (e.g., 0.1 µF) close to the VCC and VCCIO pins to reduce noise.
• EEPROM Programming: Use FTDI's FT_PROG utility to program the integrated EEPROM.
• Reset Pin: Tie the RESET# pin to VCC through a pull-up resistor if not used.
• Thermal Management: Ensure adequate ventilation or heat dissipation for reliable operation in high-temperature environments.

The FT245RL can be used to interface an Arduino UNO with a USB host. Below is an example Arduino sketch to read data from the FT245RL:

// Example code to read data from FT245RL using Arduino UNO
#define RXF 2  // Pin 2 connected to RXF# of FT245RL
#define RD  3  // Pin 3 connected to RD# of FT245RL
#define D0  4  // Pin 4 connected to D0 of FT245RL
#define D1  5  // Pin 5 connected to D1 of FT245RL
#define D2  6  // Pin 6 connected to D2 of FT245RL
#define D3  7  // Pin 7 connected to D3 of FT245RL

void setup() {
  pinMode(RXF, INPUT);  // RXF# is an input signal
  pinMode(RD, OUTPUT);  // RD# is an output signal
  pinMode(D0, INPUT);   // Data bus pins are inputs
  pinMode(D1, INPUT);
  pinMode(D2, INPUT);
  pinMode(D3, INPUT);
  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
    delayMicroseconds(1);         // Small delay for data setup
    int data = (digitalRead(D3) << 3) | (digitalRead(D2) << 2) |
               (digitalRead(D1) << 1) | digitalRead(D0);  // Read 4-bit data
    digitalWrite(RD, HIGH);       // De-assert RD#
    Serial.println(data, HEX);    // Print data in hexadecimal format
  }
}

1. Device Not Recognized by Host

   • Ensure the USB D+ and D- lines are correctly connected.
   • Verify that the pull-up resistor on the D+ line is properly installed.
   • Check the USB cable and connector for damage.

2. No Data Transfer

   • Confirm that the RXF# and TXE# signals are being monitored correctly.
   • Verify that the RD# and WR signals are being toggled as required.
   • Ensure the FIFO data bus (D0-D7) is correctly connected.

3. EEPROM Programming Fails

   • Ensure the FT_PROG utility is installed and configured correctly.
   • Verify that the EECS, EESK, and EEDATA pins are properly connected.

1. Can the FT245RL operate at 5V?

   • Yes, the FT245RL supports 5V operation for its I/O pins when VCCIO is set to 5V. However, the core voltage (VCC) must always be 3.3V.

2. What is the maximum data transfer rate?

   • The FT245RL supports data transfer rates of up to 1 MB/s.

3. **Is an external crystal required?