PRU SPI Example

gistfile1.txt

#define NOP   MOV r0, r0, r0

#define SPI_TX  r8.w0

#define SPI1_SCLK   R30.t7
#define SPI1_MOSI   R30.t14
#define SPI1_MISO   R31.t15
#define SPI1_CS0    R30.t0
#define SPI1_CS1    R30.t1
#define SPI1_CS     SPI1_CS0

#define LSPD_SPI_SCLK SPI1_SCLK
#define LSPD_SPI_MOSI SPI1_MOSI
#define LSPD_SPI_MISO SPI1_MISO
#define LSPD_SPI_CS0  SPI1_CS0
#define LSPD_SPI_CS1  SPI1_CS1
#define LSPD_SPI_CS   LSPD_SPI_CS1

#define LSPD_CNVST    R30.t3


.macro SPI_XFER_BIT
.mparam LS_RX, BIT

    // Output LSPD control
    QBBS MOSI_HIGH, SPI_TX, BIT
    CLR LSPD_SPI_MOSI
    JMP MOSI_DONE
    MOSI_HIGH:
    SET LSPD_SPI_MOSI
    NOP
    MOSI_DONE:

    SET LSPD_SPI_SCLK

    // Read LSPD - Set b0 of R11 to MISO
    QBBC MISO_LOW, LSPD_SPI_MISO
    SET LS_RX, LS_RX, BIT
    JMP MISO_DONE
    MISO_LOW:
    NOP
    NOP
    MISO_DONE:

    CLR LSPD_SPI_SCLK

    NOP
    NOP

.endm

.macro SPI_XFER_WORD
.mparam LS_RX

    SPI_XFER_BIT LS_RX, 15
    SPI_XFER_BIT LS_RX, 14
    SPI_XFER_BIT LS_RX, 13
    SPI_XFER_BIT LS_RX, 12
    SPI_XFER_BIT LS_RX, 11
    SPI_XFER_BIT LS_RX, 10
    SPI_XFER_BIT LS_RX, 9
    SPI_XFER_BIT LS_RX, 8
    SPI_XFER_BIT LS_RX, 7
    SPI_XFER_BIT LS_RX, 6
    SPI_XFER_BIT LS_RX, 5
    SPI_XFER_BIT LS_RX, 4
    SPI_XFER_BIT LS_RX, 3
    SPI_XFER_BIT LS_RX, 2
    SPI_XFER_BIT LS_RX, 1
    SPI_XFER_BIT LS_RX, 0

.endm