UART vs USI

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What is the difference between UART (2313) and USI (tiny26)?

How would the implementation differ for 1-wire parts (DS18S20)?
Would I need a max232 chip for use in something like MIDI implementation?

Hope this isn't a too loaded question.

Marc

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Well, i can answer some of the question. UART is assincronous comunication, and can be half or full duplex, the uart is teh same of PC. USI is universal sincronous interface, and can be used like SPI or a simple I2C. The max232 chip is used to convert TTL signals to RS232 signal, the PC serial port uses RS232 signal, that why you need the chip to convert signals to AVR for example.

Hope that was some help,
FK.

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The UART on the 2313 "just works" and the USI on the Tiny26 is nearly incomprehensible.

Whether you need a line driver like the MAX232 is kind of a toss-up. Many (most?) PCs will accept a CMOS level (0-5) signal. If this is a commercial app you should use the line driver to ensure it will work, but if it is a basement project you can just test it without and see if your PC takes it. You will need to invert the signals, though.

MAX232- chip+4 caps=always works
No MAX232- two transistors, two diodes, four resistors=may work

There is a MAX233, too, which requires no external components. Costs more, though.

Hope this wasn't too loaded an answer.

j.

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may i recommend the ds275 - an 8 pin ttl rs232 converter? only works for half duplex protocols but ds/maxim sends out samples at your command

/claus

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RS232 is not MIDI.

RS232 converters are *NOT* used for MIDI. MIDI is driven by an open collector such as 7407, or sometimes just a single transistor. It's received by an opto isolator. A clever person may adapt an RS232 signal to MIDI with several diodes, but why?

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