35 lines
1.1 KiB
Plaintext
35 lines
1.1 KiB
Plaintext
Soft SPI
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The soft SPI bus implementation allows the use of GPIO pins to simulate a
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SPI bus. No SPI host is required for this to work. The down-side is that the
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performance will typically be much lower than a real SPI bus.
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The soft SPI node requires the following properties:
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compatible: "u-boot,soft-spi"
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soft_spi_cs: GPIO number to use for SPI chip select (output)
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soft_spi_sclk: GPIO number to use for SPI clock (output)
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soft_spi_mosi: GPIO number to use for SPI MOSI line (output)
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soft_spi_miso GPIO number to use for SPI MISO line (input)
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spi-delay-us: Number of microseconds of delay between each CS transition
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The GPIOs should be specified as required by the GPIO controller referenced.
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The first cell holds the phandle of the controller and the second cell
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typically holds the GPIO number.
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Example:
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soft-spi {
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compatible = "u-boot,soft-spi";
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cs-gpio = <&gpio 235 0>; /* Y43 */
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sclk-gpio = <&gpio 225 0>; /* Y31 */
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mosi-gpio = <&gpio 227 0>; /* Y33 */
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miso-gpio = <&gpio 224 0>; /* Y30 */
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spi-delay-us = <1>;
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#address-cells = <1>;
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#size-cells = <0>;
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cs@0 {
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};
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};
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