Question on using MPC8306 as i2c slave

jiaguo — Fri, 13 Sep 2013 03:31:44 GMT

Hi buddies,

I'm developing an i2c slave driver using linux 2.6.34 on MPC8306.

In my test, I use a RS232-to-I2C adapter connected to PC as the i2c master.

When doing master receive and slave transmit, when the last byte has been xfered,

the slave always pull the I2C_SDA low and doesn't release the i2c bus,

STOP can't be received. The datasheet seems doesn't make it clear that how to

release I2C_SDA. Is there anybody facing the same issue?

Please help, thanks in advance.:smileysilly:

As the i2c protocol says, no ACK on the last byte transmit before STOP, and I found

I2CnSR register RXAK bit set, which mean no ACK is received. So, I think the slave

hang the bus and waiting for ACK from master.

Below is my i2c slave driver interrupt routine.

static irqreturn_t fsl_i2cli_irq_handler(int irq, void *device_id)
{
    struct fsl_i2cli_priv *i2cli = device_id;

    if (i2cli != fsl_i2cli)
        return IRQ_HANDLED;

    if ((readb(i2cli->base + MPC_I2C2SR) & I2C2SR_MIF) == 0)
        return IRQ_HANDLED;

    /* If we are addressed as slave, check I2CnSR[SRW] and
       set I2CnCR[MTX] accordingly */
    if (readb(i2cli->base + MPC_I2C2SR) & I2C2SR_MAAS) {
        int tmp;
        u8 cr, x;

        PDEBUG("#### Addressed as an i2c slave ####\n");
           
        tmp = readb(i2cli->base + MPC_I2C2SR) & I2C2SR_SRW;
        i2cli->mode = tmp > 0 ? 1 : 0;

        PDEBUG("xfer mode: %s\n", (i2cli->mode == 0 ?
                "Slave receive" : "Slave transmit"));

        cr = readb(i2cli->base + MPC_I2C2CR);
        if (i2cli->mode == 0)
            writeb((cr & ~I2C2CR_MTX), i2cli->base + MPC_I2C2CR);
        else if (i2cli->mode == 1)
            writeb((cr | I2C2CR_MTX), i2cli->base + MPC_I2C2CR);

        writeb(0, i2cli->base + MPC_I2C2SR);

        /* dummy read on first byte */
        x = readb(i2cli->base + MPC_I2C2DR);
        PDEBUG("Dummy read x: 0x%02x\n", x);
    }

    /* Set by the falling edge of the 9th clock of a byte transfer */
    if (readb(i2cli->base + MPC_I2C2SR) & I2C2SR_MCF) {
        PDEBUG("Data xfered\n");
       
        writeb(0, i2cli->base + MPC_I2C2SR);

        /* If it's ACK on Master START command, do a dummy read */
        if (!i2cli->f_ack_on_start) {
            readb(i2cli->base + MPC_I2C2DR);
            i2cli->f_ack_on_start = 1;
            goto verify_mbb;
        }
   
        /* Data xfer buffer is full */   
        if ((i2cli->mode == 0) &&
                (i2cli->buf_ptr - i2cli->buf >= I2CLI_XFER_BUF_SIZE)) {
            i2cli->xfer_done = 1;
            wake_up_interruptible(&i2cli->wait_qh);
            goto end;
        }

        /* No more data to xfer in slave transmit mode */
        if ((i2cli->mode == 1) && (i2cli->buf_ptr - i2cli->buf >= i2cli->size)) {
            i2cli->xfer_done = 1;
            wake_up_interruptible(&i2cli->wait_qh);
            goto end;
        }

        if (i2cli->mode == 0) {
            /* Slave receive */
            u8 data = readb(i2cli->base + MPC_I2C2DR);
            PDEBUG("Read data: 0x%02x\n", data);
            PDEBUG("buf: %p, buf_ptr: %p\n", i2cli->buf, i2cli->buf_ptr);
            i2cli->size++;
            *i2cli->buf_ptr++ = data;
        } else {
            /* Slave transmit */
            writeb(*i2cli->buf_ptr, i2cli->base + MPC_I2C2DR);
            PDEBUG("Write data: 0x%02x\n", *i2cli->buf_ptr);
            PDEBUG("buf: %p, buf_ptr: %p\n", i2cli->buf, i2cli->buf_ptr);
            i2cli->buf_ptr++;
        }
    }

verify_mbb:
   
    /* If a STOP condition is detected, I2CnSR[MBB] is cleared,
     * Seems only make effect in case of slave receive */
    if ((readb(i2cli->base + MPC_I2C2SR) & I2C2SR_MBB) == 0) {
        PDEBUG("Stoped\n");
        i2cli->xfer_done = 1;
        wake_up_interruptible(&i2cli->wait_qh);
    }

end:
    return IRQ_HANDLED;
}

Message was edited by: Jia Guo

PowerQUICC ProcessorsのトピックQuestion on using MPC8306 as i2c slave

Question on using MPC8306 as i2c slave