Chapter 2. API Reference
This may be a data OUT phase, in which the direction is slave to master, or a data IN phase, in
which the direction is master to slave.
The direction means which side (master or slave) controls the MOSI, MISO, WP and HD pins.
Data IO Modes In some IO modes, more data wires can be use to send the data. As a result, the SPI clock cycles
required for the same amount of data will be less than in 1-bit mode. For example, in QIO mode, address and data
(IN and OUT) should be sent on all 4 data wires (MOSI, MISO, WP, and HD). Here’s the modes supported by
ESP32-S2 SPI slave and the wire number used in corresponding modes.
Mode command WN address WN dummy cycles data WN
1-bit 1 1 1 1
DOUT 1 1 4 2
DIO 1 2 4 2
QOUT 1 1 4 4
QIO 1 4 4 4
QPI 4 4 4 4
Normally, which mode is used is determined is determined by the command sent by the master (See Supported
Commands), except from the QPI mode.
QPI Mode The QPI mode is a special state of the SPI Slave. The master can send ENQPI command to put the
slave into the QPI mode state. In the QPI mode, the command is also sent in 4-bit, thus it’s not compatible with
the normal modes. The master should only send QPI commands when the slave is in the QPI mode. To exit form the
QPI mode, master can send EXQPI command.
Supported Commands
Note: The command name are in a master-oriented direction. For example, WRBUF means master writes the
buffer of slave.
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