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SPI - Serial Peripheral Interface

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  • KEYWORDS: Peripheral,Peripherals,Serial Peripheral Interface,SPI,Built-In

The Serial Peripheral Interface is a Serial Bus for peripherals that uses Clock, Data In, and Data Out (and often a Chip Select pin).

See SPI Class in the reference

Hardware SPI

On most boards there are hardware SPI peripherals. Check out the pin diagram on the reference page for your board and look for pins marked with an SPI tag.

You can use it as follows.

// set up SPI
SPI1.setup({mosi:B5, miso:B4, sck:B3});

// write data without a response

// write data with a response
var d = SPI1.send([1,2,3,4]);

See the reference for SPI.setup for more information on the arguments that can be passed in.

Software SPI

If you don't have access to your board's pins, you can also emulate SPI in software:

// set up SPI
var spi = new SPI();
spi.setup({mosi:B5, miso:B4, sck:B3});

// write data without a response

// write data with a response
var d = spi.send([1,2,3,4]);

Speed (baud rate)

Pretty much all SPI devices are guaranteed to support 100kBits/sec transfer speed, so that is the default in Espruino. However you can specify higher speeds with bitrate in SPI.setup if your device supports it, eg:

SPI1.setup({ mosi:B5, miso:B4, sck:B3, baud: 400000 });

Note: baud rate is ignored for software SPI - it will always send as fast as possible.

Using SPI