4/17/2024 0 Comments Arduino mega 2560 ss pinWhenever an interrupt is generated due to data from the master device, in Slave, the pointer will jump to ISR with the address of SPI_STC_vect, and it will copy the data from SPDR to variable c and finally from c to the str array. Also, you need to attach interrupt so that you can handle the data received by the Master. To use the Arduino board as a Slave device, you need to set the MISO pin as output and turn ON the Slave mode. Str = c // save data in the next index in the array buff Serial.println(str) //print the array on serial monitorĬhar c = SPDR // read byte from SPI Data Register SPI.attachInterrupt() // turn on interrupt SPCR |= _BV(SPE) // turn on SPI in slave mode PinMode(MISO, OUTPUT) // have to send on Master in so it set as output Serial.println("Hello I'm SPI UNO_SLAVE") Serial.begin (115200) // set baud rate to 115200 for usart digitalWrite(SS, LOW) // enable Slave SelectĭigitalWrite(SS, HIGH) // disable Slave SelectĪrduino Code for Slave Mode #include "SPI.h" Now, in the void loop, you need to set CS/SS pin as low to select the slave device, then you can transfer the data using SPI.transfer, and finally, in the end, set CS/SS pin as high to disable the slave connection. The default setting is SPI_CLOCK_DIV4, which sets the SPI clock to one-quarter of the frequency of the system clock (5 Mhz for the boards at 20 MHz). SPI.setClockDivider(divider) function is to Set the SPI clock divider relative to the system clock. The below table shows the SCK clock frequency select bit settings. CPOLīit 1:0 are SPR1-SPR0 SPI Clock Rate Select bits. If the bit is set, then the data sample is on the trailing clock edge, and if it is clear, then the data sample is on the leading clock edge. If set, clocks start from logic one, and if clear, the clock starts from logic zero.īit 2 is CPHA, Clock Phase Select bit.The Clock Polarity (CPOL) and Clock Phase (CPHA) bits define how serial data is transferred between the Master and the Slave. Set for Master mode and clear the bit for Slave mode.īit 3 is CPOL, Clock Polarity Select bit. If the bit is clear, then MSB is transmitted first.īit 4 is MSTR, Master/Slave Select bit. If the bit is set, then it transmits LSB first. You need to set this bit high to enable the SPI.īit 5 is DORD, Data Order bit. You can enable SPI Interrupt by setting the bit high and disabling it by setting the bit low.īit 6 is SPE, SPI Enable bit. SPI Master-Slave Interfacingīit 7 is SPIE, SPI Interrupt Enable bit. An SPI can have only one Master and can have multiple slaves.Ī Master is usually a microcontroller, and the slaves can be a microcontroller or any peripherals such as sensors, ADC, DAC, LCD, RTC, etc. SPI communication uses four wires MISO, MOSI, CLK, and CS/SS. It is also known as the four-wire protocol. However, once the communication begins, both Master and Slave can transmit the data simultaneously. SPI device can be set as Master or Slave, and only the Master can generate clock pulses and initiate the communication. SPI is a synchronous serial communication protocol to transfer the data with rising or falling edge of clock pulse between two microcontrollers or between the microcontroller and SPI peripheral devices. This means that data can be transferred in both directions at the same time simultaneously. SPI is a synchronous serial communication and full-duplex protocol. ![]() Motorola founded SPI (Serial Peripheral Interface) interface in 1970. is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to products on. Supplies Hardware components Arduino UNO Rev3 Interfacing of RFID-RC522 Module with Arduino Uno.How to use the RFID-RC522 module (RFID reader) with the Arduino UNO.Interfacing of Arduino Uno Board and Arduino Mega Board for SPI.Interfacing of two Arduino Uno Boards for SPI.How do I connect two Arduinos with SPI?.
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