I2c Vs 2 wire serial

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Captain Haddock

Senior Member
Whats the difference between I2c & 2 wire serial, it seems to be very similar to me (the untrained eye), the device I'm looking at is a Maxim DS1803 digi-pot.
 
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Memran

Member
I'm no expert on this, but one big difference I can think of with i2c is that you send and receive data from specific devices, so if you have multiple devices at the same time you can read/write from any one you want.
I believe with serial, you must "broadcast" the data and it is up to the devices to decide whether or not to accept/respond.
 
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geoff07

Senior Member
Looks the same to me! I coded some i2c in C and the result looks the same as their traces. Perhaps they didn't want to mention Philips!

I would give it a try.

Edit: you made me curious. I found this on another datasheet, which suggests they are the same.

I2C Compatibility

The MAX520/MAX521 are quad/octal, 8-bit voltage-output
digital-to-analog converters (DACs) with simple 2-wire ser-
ial interfaces that allow communication between multiple
devices.

The MAX520/MAX521 are fully compatible with existing
I2C systems. SCL and SDA are high-impedance inputs;
SDA has an open drain which pulls the data line low
during the 9th clock pulse. Figure 11 shows a typical
I2C application.
 
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Technical

Technical

Technical Support
Staff member
i2c is a trademark and patented technology and involves royalties when embedded in a chip. For instance Microchip paid a special charge of $21.1 million in a settlement with Philips in 2004 for use of i2c and other patents in their microcontrollers. Expensive!
So many companies use a 'compatible' protocol and call it something else. It also allows them to add non-i2c 'extras' if they so choose to the protocol.
 
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KeithRB

Senior Member
I am not exactly sure what you mean by "2 wire serial", but one important difference is that I2C is clocked which theoretically allows for faster speeds. Serial timing uses the signal itself.
 
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westaust55

Moderator
KeithRB said:
I am not exactly sure what you mean by "2 wire serial", but one important difference is that I2C is clocked which theoretically allows for faster speeds. Serial timing uses the signal itself.
Click to expand...
Two Wire Interface (TWI) is basically another name for i2c which is a clocked serial comms protocol.
SPI is Serial Peripheral Interface which is also a clocked protocol.
Other serial interfaces are based or more strict timing and do not need a separate clock signal such as the PICAXE SEROUT and SERIN commands.
 
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