Skip to content

Tsop752 Infrared Receiver






The Tsop752 is an infrared (IR) receiver module for IR remote control systems. The device detects modulated IR signals and outputs a de-modulated signal to be processed by a micro-controller.

The device data-sheet can be found here.


The Tsop752 outputs IR data frames which consist of a de-modulated pulse train. The PulseCapture module is used to capture incoming pulses of each frame from the device. When a rising or falling edge of a signal is detected, a timestamp in microseconds is recorded. The logic levels of the data in the received frame is determined by examining the period of each pulse.

In addition to the capture module, the Timer module will be utilized to determine the end of transmission frame when no consecutive pulse is received within a timeout period after the last received pulse.

Detailed Design


namespace sjsu
class Tsop752 final : public InfraredReceiver
  explicit Tsop752(sjsu::PulseCapture & capture,
                   sjsu::Timer & timer,
                   std::chrono::microseconds timeout);

  Status Initialize() override;
  void SetInterruptCallback(DataReceivedHandler handler) override;
  void HandlePulseCaptured(PulseCapture::CaptureStatus_t status);
  void HandleEndOfFrame();

  const sjsu::PulseCapture & capture_;
  const sjsu::Timer & timer_;
  const std::chrono::microseconds kTimeout;
  DataFrame_t data_frame_;
  bool is_start_of_new_frame_;
  uint32_t last_received_timestamp_;
  DataReceivedHandler user_callback_ = nullptr;
}  // namespace sjsu


Status Initialize() const override
The following sequence is performed to initialize the driver: 1. Initialize and configure capture_. If the peripheral fails to initialize, the failure status shall be returned. 2. Initialize and configure timer_. 3. Return Status::kSuccess if both drivers are initialize successfully, Otherwise return the failure Status.

Capturing and Handling the De-modulated IR signal

void SetInterruptCallback(DataReceivedHandler handler) const override
SetInterruptCallback sets the user_callback_ that is invoked when a data frame is successfully received.

void HandlePulseCaptured(PulseCapture::CaptureStatus_t status)
The capture module is configured to increment at 1MHz (1µs). HandlePulseCaptured is invoked when a pulse edge is detected and the value of Capture Register, CRn, will serve as a timestamp for when the edge was detected. The duration of the pulse is determined by calculating the difference of the previously received timestamp and the current timestamp. Additionally, upon capturing a pulse edge, the timer is reset and restarted.

void HandleEndOfDataFrame()
HandleEndOfDataFrame is invoked when one of the following conditions is met: 1. The timeout period of the timer is reached after receiving a pulse edge. 2. The data_frame's pulse_buffer_length reaches the kMaxPulseBufferSize.

This signifies the end of the transmission frame and the user_callback_ is invoked to allow the received data frame to be further processed.


For the LPC17xx and LPC40xx series MCU, the PulseCapture and Timer peripherals must not share the same channels. Each channel for both peripherals share the same NVIC. Due to the implementation of both peripherals, initializing the peripherals with the same channel will cause the interrupt callback to be overwritten. For example, suppose PulseCapture and Timer are initialized using the same channel with interrupts enabled. If the Timer was last to be initialized, only the interrupt callbacks of the Timer peripheral will be invoked.

Future Advancements


Testing Plan

Unit Testing Scheme

The PulseCapture and Timer modules shall be mocked and stubbed to provide test inputs for the Tsop752 driver.

The following functions shall be tested: 1. Initialize() - Should return the failure Status when Initialize of PulseCapture is stubbed to return a Status that is not Status::kSuccess. - Should return the failure Status when Initialize ofTimer is stubbed to return a Status that is not Status::kSuccess. - Should return Status::kSuccess when Initialize of both Capture and Timer are stubbed to return Status::kSuccess. 2. HandlePulseCaptured() - Test input timestamps: { 0, 9'000, 13'500, 14'060, 15'750, 16'310 } shall be used. - At each iteration, the method should: - Invoke the Reset and Start methods of Timer once. 3. HandleEndOfFrame() - Test input timestamps: { 0, 9'000, 13'500, 14'060, 15'750, 16'310 } shall be used. - The method should: - Invoke the Stop method of Timer once. - Invoke the mocked user callback. - The resulting pulse buffer should be equivalent to { 9'000, 4'500, 560, 1'690, 560 } - The data frame's pulse_buffer_length should be 5.

Demonstration Project

A demonstration project using the LPC17xx platform to receive remote control signals from a NEC remote can be found here.