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Showing posts from June, 2010

RC-5 Protocol (InfraRed)

We have all used InfraRed based remotes to control various appliances around our house. All these remote work by transmitting data in form of flashes of infrared light - and wherever one needs to transmit data, there is always a protocol involved. The RC-5 protocol from Philips has been used in TVs, VCRs and other appliances since the past three decades. It was developed by Philips but was adopted by many other manufacturers.
Now days RC-5 has been superseded by RC-6 and various other protocols from various other manufacturers. These newer protocols have better features and are more flexible. San Bergmans's KnowledgeBase on Consumer IR is a nice place to lookup information (protocol specs, circuits, embedded code) on any of the old or new IR based protocols.

Here is how a RC-5 TV remote control transmitter unit looks like:





And here is a InfraRed receiver/demodulator:



A RC-5 codeword is 14 bit long. The first two are the start bits, then comes the toggle bit and finally the 5 bits of a…

I2S

I2S stands for Inter Integrate Sound and is similar to the I2C which is used for transmitting data between Chips on a circuit board. (wikipedia article on I2S). I2S is used for connecting digital audio devices together, (for example between the main processor and the audio codec chip on cell phones or computers or between the CD transport and the DAC in a CD player).
I2S interface consists of atleast 3 signals: ClockLeft right clock
Data line
The eKA8562A Chip which is a USB Audio Controller (and can be used as an oscilloscope) sports an I2S interface. Here are a few signals captured at the various pins (I2S output) on this chip:


Pin 5 of eKA8562A - I2S BCLK Output
Clock - This signal is used as the clock to latch in the bits appearing on the data line.




Pin 6 of eKA8562A - I2S LRCLK Output
Left Right Clock - This signal is used to tell the receiving device whether the data being received by it on the data line is meant for the left audio channel or the right audio channel.




Pin 7 of eKA8562A…