SPI
About
For some APIs, the reference to be used is the same as the Arduino Core.
Example
To get started with SPI, you can try:
SPI Multiple Buses
/* The ESP32 has four SPi buses, however as of right now only two of
* them are available to use, HSPI and VSPI. Simply using the SPI API
* as illustrated in Arduino examples will use VSPI, leaving HSPI unused.
*
* However if we simply initialize two instance of the SPI class for both
* of these buses both can be used. However when just using these the Arduino
* way only will actually be outputting at a time.
*
* Logic analyzer capture is in the same folder as this example as
* "multiple_bus_output.png"
*
* created 30/04/2018 by Alistair Symonds
*/
#include <SPI.h>
// Define ALTERNATE_PINS to use non-standard GPIO pins for SPI bus
#ifdef ALTERNATE_PINS
#define VSPI_MISO 2
#define VSPI_MOSI 4
#define VSPI_SCLK 0
#define VSPI_SS 33
#define HSPI_MISO 26
#define HSPI_MOSI 27
#define HSPI_SCLK 25
#define HSPI_SS 32
#else
#define VSPI_MISO MISO
#define VSPI_MOSI MOSI
#define VSPI_SCLK SCK
#define VSPI_SS SS
#define HSPI_MISO 12
#define HSPI_MOSI 13
#define HSPI_SCLK 14
#define HSPI_SS 15
#endif
#if CONFIG_IDF_TARGET_ESP32S2 || CONFIG_IDF_TARGET_ESP32S3
#define VSPI FSPI
#endif
static const int spiClk = 1000000; // 1 MHz
//uninitialised pointers to SPI objects
SPIClass *vspi = NULL;
SPIClass *hspi = NULL;
void setup() {
//initialize two instances of the SPIClass attached to VSPI and HSPI respectively
vspi = new SPIClass(VSPI);
hspi = new SPIClass(HSPI);
//clock miso mosi ss
#ifndef ALTERNATE_PINS
//initialize vspi with default pins
//SCLK = 18, MISO = 19, MOSI = 23, SS = 5
vspi->begin();
#else
//alternatively route through GPIO pins of your choice
vspi->begin(VSPI_SCLK, VSPI_MISO, VSPI_MOSI, VSPI_SS); //SCLK, MISO, MOSI, SS
#endif
#ifndef ALTERNATE_PINS
//initialize hspi with default pins
//SCLK = 14, MISO = 12, MOSI = 13, SS = 15
hspi->begin();
#else
//alternatively route through GPIO pins
hspi->begin(HSPI_SCLK, HSPI_MISO, HSPI_MOSI, HSPI_SS); //SCLK, MISO, MOSI, SS
#endif
//set up slave select pins as outputs as the Arduino API
//doesn't handle automatically pulling SS low
pinMode(vspi->pinSS(), OUTPUT); //VSPI SS
pinMode(hspi->pinSS(), OUTPUT); //HSPI SS
}
// the loop function runs over and over again until power down or reset
void loop() {
//use the SPI buses
spiCommand(vspi, 0b01010101); // junk data to illustrate usage
spiCommand(hspi, 0b11001100);
delay(100);
}
void spiCommand(SPIClass *spi, byte data) {
//use it as you would the regular arduino SPI API
spi->beginTransaction(SPISettings(spiClk, MSBFIRST, SPI_MODE0));
digitalWrite(spi->pinSS(), LOW); //pull SS slow to prep other end for transfer
spi->transfer(data);
digitalWrite(spi->pinSS(), HIGH); //pull ss high to signify end of data transfer
spi->endTransaction();
}