IR - Transmit IR Sony Data

• AmebaD [ AMB21 / AMB22 / BW16 / AW-CU488 Thing Plus / AMB25 / AMB26 ] x 2
• Grove – Infrared Emitter x1

Introduction

In this example, we use one Ameba RTL8722 modules that connecting with an infrared (IR) Emitter to transmit and receive IR SONY data “0xA90” (Sony TV power code). For the receiver side, you can either use an oscilloscope/logic analyser to view the waveform and decode accordingly.

Figure 1: Grove – Infrared Transmitter

On the transmission side, the transmitter will send IR SONY data. For more details, please refer to SB-Projects’ topic of IR Remote Control Theory to learn the theory of IR remote controls operation and a collection of IR protocol descriptions. In this example, we are going to use Sony as the transmission protocol.

Sony Features
• 12-bit version, 7 command bits, 5 address bits.
• Pulse width modulation.
• Carrier frequency of 40kHz.
• Bit time of 1.2ms or 0.6ms.

Sony SIRC Modulation
The SIRC protocol uses pulse width encoding of the bits. The pulse representing a logical “1” is a 1200us long burst of the 40kHz carrier, while the burst width for a logical “0” is 600us long. All bursts are separated by a 600us long space interval as shown in Figure 2 below.

Figure 2: Sony SIRC Modulation

Protocol

Figure 3: 12-bit Sony SIRC protocol

The Figure 3 above shows a typical pulse train of the 12-bit SIRC protocol. With this protocol the LSB is transmitted first. The start burst is always 2.4ms wide, followed by a standard space of 0.6ms. Apart from signalling the start of a SIRC message this start burst is also used to adjust the gain of the IR receiver. Then the 7-bit Command is transmitted, followed by the 5-bit Device address. In this case Address 1 and Command 19 is transmitted.
Commands are repeated every 45ms (measured from start to start) for as long as the key on the remote control is held down.

Procedure