Multiple SS/CS for a single SPI
Posted: Wed Jul 21, 2021 4:11 pm
In the example https://github.com/espressif/arduino-es ... _Buses.ino an abbreviated form of the example is copied at below.
What I find odd is that the xspi->begin statement has SS as an argument whereas the xspi->beginTransaction does not.
As the XSPI_SCLK, XSPI_MISO, XSPI_MOSI, pins are fixed once xspi is instantiated but XSPI_SS could have several distinct values (how many?) then should not XSPI_SS be specified in xspi->beginTransaction?
Or should it be that to address a different device one should have:
Or perhaps something else?
Thanks.
What I find odd is that the xspi->begin statement has SS as an argument whereas the xspi->beginTransaction does not.
As the XSPI_SCLK, XSPI_MISO, XSPI_MOSI, pins are fixed once xspi is instantiated but XSPI_SS could have several distinct values (how many?) then should not XSPI_SS be specified in xspi->beginTransaction?
Or should it be that to address a different device one should have:
Code: Select all
xspi->begin(SS1)
xspi->beginTransaction
xspi->end
xspi->begin(SS2)
xspi->beginTransaction
xspi->endThanks.
Code: Select all
void setup() {
//initialise two instances of the SPIClass attached to VSPI and HSPI respectively
vspi = new SPIClass(VSPI);
hspi = new SPIClass(HSPI);
vspi->begin(VSPI_SCLK, VSPI_MISO, VSPI_MOSI, VSPI_SS);
hspi->begin(HSPI_SCLK, HSPI_MISO, HSPI_MOSI, HSPI_SS);
//set up slave select pins as outputs as the Arduino API
//doesn't handle automatically pulling SS low
pinMode(VSPI_SS, OUTPUT); //VSPI SS
pinMode(HSPI_SS, OUTPUT); //HSPI SS
}
void loop() {
vspiCommand();
delay(100);
hspiCommand();
delay(100);
}
void vspiCommand() {
byte data = 0b01010101; // junk data to illustrate usage
//use it as you would the regular arduino SPI API
vspi->beginTransaction(SPISettings(spiClk, MSBFIRST, SPI_MODE0));
digitalWrite(VSPI_SS, LOW); //pull SS slow to prep other end for transfer
vspi->transfer(data);
digitalWrite(VSPI_SS, HIGH); //pull ss high to signify end of data transfer
vspi->endTransaction();
}
void hspiCommand() {
byte stuff = 0b11001100;
hspi->beginTransaction(SPISettings(spiClk, MSBFIRST, SPI_MODE0));
digitalWrite(HSPI_SS, LOW);
hspi->transfer(stuff);
digitalWrite(HSPI_SS, HIGH);
hspi->endTransaction();
}