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SPI
This library provides SPI communications, enabling communications with two or more microcontrollers, with the GR-LYCHEE board as the master device. It is shared with SPI communication of ESP32. When communicating with ESP32, specify PIN_ESP_IO15 (pin 37) as SS. A separate SPI channel (SPI2) is connected to the SD card. To use this library, specify #include <SPI.h>.
SPISettings
- Description
- Each SPI device can be configured once as an SPISettings object.
- Syntax
- SPISettings mySetting(speed, dataOrder, datamode)
- Parameters
- speed: The speed of the communication
dataOrder: MSBFIRST or LSBFIRST
dataMode: SPI_MODE0, SPI_MODE1, SPI_MODE2, or SPI_MODE3 - Returns
- None
begin
- Description
- Initializes the SPI bus by setting SCK, MOSI and SS to outputs, pulling SCK and MOSI low, and SS high.
- Syntax
- SPI.begin()
- Parameters
- None
- Returns
- None
end
- Description
- Disables the SPI bus, and returns the pin to a general I/O port.
- Syntax
- SPI.end()
- Parameters
- None
- Returns
- None
beginTransaction()
- Description
- Initializes the SPI bus using the defined SPISettings.
- Syntax
- SPI.beginTransaction(mySettings)
- Parameters
- mySettings: The chosen settings according to SPISettings
- Returns
- None
endTransaction()
- Description
- Stop using the SPI bus. Normally, this is called after de-asserting the chip select, to allow other libraries to use the SPI bus.
- Syntax
- SPI.endTransaction()
- Parameters
- None
- Returns
- None
setBitOrder
- Description
- Sets the order of the bits shifted out of and into the SPI bus.
- Syntax
- SPI.setBitOrder(bitOrder)
- Parameters
- bitOrder: Bit order, either LSBFIRST or MSBFIRST. Default is MSBFIRST
- Returns
- None
setClockDivider
- Description
- Sets the SPI clock divider relative to the system clock.
- Syntax
- SPI.setClockDivider(divider)
- Parameters
- divider: Set one of the following:
SPI_CLOCK_DIV2: 8MHz
SPI_CLOCK_DIV4: 4MHz (default)
SPI_CLOCK_DIV8: 2MHz
SPI_CLOCK_DIV16: 1MHz
SPI_CLOCK_DIV32: 500kHz
SPI_CLOCK_DIV64: 250kHz
SPI_CLOCK_DIV128: 125kHz - Returns
- None
setDataMode
- Description
- Sets the SPI data mode: That is, clock polarity and phase.
- Syntax
- SPI.setDataMode(mode)
- Parameters
- mode: Set one of the following. Default is Mode 0. SDMMC is not available in Modes 2 and 3.
SPI_MODE0: Clock is low during idling, samples data at rising edge
SPI_MODE1: Clock is low during idling, samples data at falling edge
SPI_MODE2: Clock is high during idling, samples data at rising edge
SPI_MODE3: Clock is high during idling, samples data at falling edge - Returns
- None
transfer
- Description
- Transfers one byte over the SPI bus, both sending and receiving.
- Syntax
- SPI.transfer(value)
- Parameters
- value: A byte of data
- Returns
- The byte read from the bus.
Sample Program
#include <Arduino.h>
#include <SPI.h>
void setup(){
SPI.begin();
}
void loop(){
//write
SPI.transfer(0x55);
//read
uint8_t data = SPI.transfer(0xff);
}
