spi_slave

machine Module

Class SPI

SLAVE mode

Slave mode allows other SPI masters to acces the K210 slave buffer memory.

Slave buffer can be configured as memory area of 512B ~ 1MB, with optional read only area at the end of the buffer.
Master can read from or write to slave buffer (except to the read only area.

Master <-> Slave communication is performed using the simple communication protocol:

• Master sends to the slave a command block requesting specific operation
• Master reads or sends data from/to slave depending on the requested operation

Command block

Before reading or writting any data, master must send to slave the 8-bytes command block describing the specific operation.
The structure of the command block is as follows:

Position	Length	Desctiption
0	1	Command code
1	3	24-bit slave buffer address
4	3	24-bit data size or special meaning, depending on command
7	1	CSUM byte, generated as xor operation over 1st 7 bytes

Here is a typical Python code used to generate the command block:

def setcmd(cmd, addr, size):
    spi_cmd = bytearray(8)
    spi_cmd[7] = 0
    spi_cmd[0] = cmd;
    spi_cmd[1] = addr & 0xff
    spi_cmd[2] = (addr >> 8) & 0xff
    spi_cmd[3] = (addr >> 16) & 0xff
    spi_cmd[4] = size & 0xff
    spi_cmd[5] = (size >> 8) & 0xff
    spi_cmd[6] = (size >> 16) & 0xff
    for i in range(7):
        spi_cmd[7] ^= spi_cmd[i]
    return spi_cmd

The following commands are accepted by K210 SPI slave:

Command code	Command	Description
1	SLAVE_CMD_TEST	Test command, slave responds by sending requeste number of bytes of requested value address field must be set to the requested byte balue (0~255) size field must be set to the requested number of bytes
2	SLAVE_CMD_INFO	Request K210 SPI slave info Slave send the 18-byte info block containing the slave driver version, size of the slave buffer and size of the read only area See below for more information
3	SLAVE_CMD_STATUS	Request the status of the previously executed command Slave responds by sending 26-bytes status block See below for more information
4	SLAVE_CMD_WRITE	Master writes data block to slave buffer. address field must be set to the slave buffer address size field must be set to the data block size
5	SLAVE_CMD_WRITE_CSUM	Master writes data block to slave buffer. address field must be set to the slave buffer address size field must be set to the data block size 2-bytes CRC16 csum must be appended to the data block by the master
6	SLAVE_CMD_READ	Master reads data block from slave buffer. address field must be set to the slave buffer address size field must be set to the data block size
7	SLAVE_CMD_READ_CSUM	Master reads data block from slave buffer. address field must be set to the slave buffer address size field must be set to the data block size 2-bytes CRC16 csum is appended to the data block by the slave