i2c_sam3.c

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#include "cfg/cfg_i2c.h"

#define LOG_LEVEL  I2C_LOG_LEVEL
#define LOG_FORMAT I2C_LOG_FORMAT

#include <cfg/log.h>

#include <hw/hw_cpufreq.h>  // CPU_FREQ
#include <cfg/debug.h>
#include <cfg/macros.h> // BV()
#include <cfg/module.h>
#include <cpu/detect.h>
#include <cpu/irq.h>
#include <cpu/power.h>
#include <drv/timer.h>
#include <drv/i2c.h>
#include <io/sam3.h>


struct I2cHardware
{
    uint32_t base;
    bool     first_xtranf;
};


INLINE bool waitTxRdy(I2c *i2c, time_t ms_timeout)
{
    ticks_t start = timer_clock();

    while (!(HWREG(i2c->hw->base + TWI_SR_OFF) & TWI_SR_TXRDY))
    {
        if (timer_clock() - start > ms_to_ticks(ms_timeout))
            return false;
        cpu_relax();
    }

    return true;
}

INLINE bool waitRxRdy(I2c *i2c, time_t ms_timeout)
{
    ticks_t start = timer_clock();

    while (!(HWREG(i2c->hw->base + TWI_SR_OFF) & TWI_SR_RXRDY))
    {
        if (timer_clock() - start > ms_to_ticks(ms_timeout))
            return false;
        cpu_relax();
    }

    return true;
}

INLINE void waitXferComplete(I2c *i2c)
{
    while (!(HWREG(i2c->hw->base + TWI_SR_OFF) & TWI_SR_TXCOMP))
        cpu_relax();
}


/*
 * The start is not performed when we call the start function
 * because the hardware should know the first data byte to send.
 * Generally to perform a byte send we should write the slave address
 * in slave address register and the first byte to send in data registry.
 * After then we can perform the start write procedure, and send really
 * the our data. To use common bertos i2c api the really start will be
 * performed when the user "put" or "send" its data. These tricks are hide
 * from the driver implementation.
 */
static void i2c_sam3_start(struct I2c *i2c, uint16_t slave_addr)
{
    i2c->hw->first_xtranf = true;

    if (I2C_TEST_START(i2c->flags) == I2C_START_R)
        HWREG(i2c->hw->base + TWI_MMR_OFF) = TWI_MMR_DADR(slave_addr >> 1) | TWI_MMR_MREAD;
    else
        HWREG(i2c->hw->base + TWI_MMR_OFF) = TWI_MMR_DADR(slave_addr >> 1);
}

static void i2c_sam3_putc(I2c *i2c, const uint8_t data)
{
    if (!waitTxRdy(i2c, CONFIG_I2C_START_TIMEOUT))
    {
        LOG_ERR("i2c: txready timeout\n");
        i2c->errors |= I2C_START_TIMEOUT;
        return;
    }

    HWREG(i2c->hw->base + TWI_THR_OFF) = data;

    if ((i2c->xfer_size == 1) && (I2C_TEST_STOP(i2c->flags) == I2C_STOP))
        HWREG(i2c->hw->base + TWI_CR_OFF) = TWI_CR_STOP;

    // On first byte sent wait for start timeout
    if (i2c->hw->first_xtranf && !waitTxRdy(i2c, CONFIG_I2C_START_TIMEOUT))
    {
        LOG_ERR("i2c: write start timeout\n");
        i2c->errors |= I2C_START_TIMEOUT;
        HWREG(i2c->hw->base + TWI_CR_OFF) = TWI_CR_STOP;
        waitXferComplete(i2c);
        return;
    }
    i2c->hw->first_xtranf = false;

    if ((i2c->xfer_size == 1) && (I2C_TEST_STOP(i2c->flags) == I2C_STOP))
        waitXferComplete(i2c);
}

static uint8_t i2c_sam3_getc(I2c *i2c)
{
    uint8_t data;
    uint32_t cr = 0;

    if (i2c->hw->first_xtranf)
    {
        cr |= TWI_CR_START;
        i2c->hw->first_xtranf = false;
    }
    if ((i2c->xfer_size == 1) && (I2C_TEST_STOP(i2c->flags) == I2C_STOP))
        cr |= TWI_CR_STOP;

    HWREG(i2c->hw->base + TWI_CR_OFF) = cr;

    if (!waitRxRdy(i2c, CONFIG_I2C_START_TIMEOUT))
    {
        LOG_ERR("i2c: read start timeout\n");
        i2c->errors |= I2C_START_TIMEOUT;
        return 0xFF;
    }

    data = HWREG(i2c->hw->base + TWI_RHR_OFF);

    if ((i2c->xfer_size == 1) && (I2C_TEST_STOP(i2c->flags) == I2C_STOP))
        waitXferComplete(i2c);

    return data;
}

static void i2c_setClock(I2c *i2c, int clock)
{
    uint32_t ck_div = 0;
    uint32_t cl_div;

    for (;;)
    {
        cl_div = ((CPU_FREQ / (2 * clock)) - 4) / (1 << ck_div);

        if (cl_div <= 255)
            break;

        ck_div++;
    }

    ASSERT(ck_div < 8);
    LOG_INFO("i2c: using CKDIV = %lu and CLDIV/CHDIV = %lu\n\n", ck_div, cl_div);

    HWREG(i2c->hw->base + TWI_CWGR_OFF) = 0;
    HWREG(i2c->hw->base + TWI_CWGR_OFF) = (ck_div << 16) | (cl_div << 8) | cl_div;
}


static const I2cVT i2c_sam3_vt =
{
    .start = i2c_sam3_start,
    .getc = i2c_sam3_getc,
    .putc = i2c_sam3_putc,
    .write = i2c_genericWrite,
    .read = i2c_genericRead,
};

struct I2cHardware i2c_sam3_hw[I2C_CNT];


void i2c_hw_init(I2c *i2c, int dev, uint32_t clock)
{
    ASSERT(dev < I2C_CNT);

    i2c->hw = &i2c_sam3_hw[dev];
    i2c->vt = &i2c_sam3_vt;

    pmc_periphEnable(PIOA_ID);

    switch (dev)
    {
        case I2C0:
            i2c->hw->base = TWI0_BASE;
            PIO_PERIPH_SEL(TWI0_PORT, BV(TWI0_TWD) | BV(TWI0_TWCK), TWI0_PERIPH);
            HWREG(TWI0_PORT + PIO_PDR_OFF) = BV(TWI0_TWD) | BV(TWI0_TWCK);
            pmc_periphEnable(TWI0_ID);
            break;
        case I2C1:
            i2c->hw->base = TWI1_BASE;
            PIO_PERIPH_SEL(TWI1_PORT, BV(TWI1_TWD) | BV(TWI1_TWCK), TWI1_PERIPH);
            HWREG(TWI1_PORT + PIO_PDR_OFF) = BV(TWI1_TWD) | BV(TWI1_TWCK);
            pmc_periphEnable(TWI1_ID);
            break;
        default:
            ASSERT(!"i2c: invalid dev number");
            return;
    }


    // Reset and set master mode
    HWREG(i2c->hw->base + TWI_CR_OFF) = TWI_CR_SWRST;
    HWREG(i2c->hw->base + TWI_CR_OFF) = TWI_CR_MSEN | TWI_CR_SVDIS;

    i2c_setClock(i2c, clock);
}