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How does SPI transfer data?
SPI is a full-duplex interface; both master and slave can send data at the same time via the MOSI and MISO lines respectively. During SPI communication, the data is simultaneously transmitted (shifted out serially onto the MOSI/SDO bus) and received (the data on the bus (MISO/SDI) is sampled or read in).
What is the byte order of SPI protocol?
The data on the SPI bus is clocked with most significant bit first. All multi-byte register data are sent in big-endian byte order.
Does SPI send MSB first?
The SPI protocol does not specify whether the most-significant bit (MSb) or least-significant bit (LSb) is transmitted or received first during an SPI transfer. Hence, most SPI devices allow this bit order to be configured.
Is MSB or LSB transmitted first?
As with bits, the MSB (byte) is normally the byte farthest to the left, or the byte transmitted first in a sequence. When the MSB in a sequence is farthest to the left (or first), the least significant bit or byte (LSB) is usually the one farthest to the right (or last).
Can you transfer more than one byte at a time?
I believe Arduino’s SPI.transfer waits to receive 8 bits after sending 8 bits. Incorrect. With SPI, a byte is clocked in at the same time as a byte is clocked out. It may be that this byte is simply a dummy byte though, if the slave has nothing to say.
How many bytes back do you get in SPI?
In the SPI protocol, you get one byte back for every one you send. If you are not interested in the response from a device, you can just ignore the return bytes. SPI has no handshaking.
How are multiple slaves connected to a SPI bus?
Even though multiple slaves are connected to the master in the SPI bus, only one slave will be active at any time. In order to select the slave, the master will pull down the SS (Slave Select) or CS (Chip Select) line of the corresponding slave. Hence, there must by a separate CS pin on the Master corresponding to each of the slave device.
How is the chip select asserted in SPI?
For multibyte transfer, you keep the chip select asserted (low) between every byte by setting the transferMode to SPI_CONTINUE in the SPI.transfer call. For the last byte, you will deassert the chip select (set it high) by setting the transferMode parameter to SPI_LAST in the SPI.transfer call..