how to use SPI

実奥山 — Mon, 04 Jun 2018 06:39:05 GMT

I want to read/write SPI SRAM by LPC54608

I want to use Interrupt,non-blocking.

I attach a qutestion.

Please answer my question.

makoto okuyama.

Re: how to use SPI

kerryzhou — Tue, 05 Jun 2018 07:40:25 GMT

Hi Customer,

You can use the interrupt mode, it's no problem.

Now, answer your question:

Take the sdk code SDK_2.3.0_LPCXpresso54608\boards\lpcxpresso54608\driver_examples\spi\interrupt_b2b\master as an example.

The SPI wave is tested as this:

The CS will be de-asserted after the last byte is sent by the interrupt.

More details, you can check SPI_MASTER_IRQHandler in spi_interrup_b2c_master.c.

Wish it helps you.

If you still have question about it, please kindly let me know.

Have a great day,
Kerry

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Re: how to use SPI

実奥山 — Wed, 06 Jun 2018 15:02:40 GMT

Dear Kerry

Thank you for your answer.

I think,

In SPI_MASTER_IRQHandler (spi\interrupt_b2b\master ), Every receiving 1 byte, interrupt occurs.

I want long interval of interrupt.

I found the sample named ."interrupt_b2b_transfer/master"

In this interrupt is SPI_MasterTransferHandleIRQ.

I think fifo for interrupt exists.

And intterupt occurs when fifo is full.

Is it correct?

In SPI_MasterTransferHandleIRQ,When last data recieved,interrupt calls Mastercallback.

In Mastercallback,masterFinished is set.

Is it correct?

Why masterFinished is set in Mastercallback?

I think ,it's no problem even if masterFinished is set in MasterTransferHandleIRQ.

Is it correct?

makoto okuyama

Re: how to use SPI

kerryzhou — Thu, 07 Jun 2018 06:50:44 GMT

Hi makoto,

If you check the SPI_MasterTransferHandleIRQ, you will find the Mastercallback is called just in SPI_MasterTransferHandleIRQ:

void SPI_MasterTransferHandleIRQ(SPI_Type *base, spi_master_handle_t *handle)
{
assert((NULL != base) && (NULL != handle));

    /* IRQ behaviour:
     * - first interrupt is triggered by empty txFIFO. The transfer function
     *   then tries empty rxFIFO and fill txFIFO interleaved that results to
     *   strategy to process as many items as possible.
     * - the next IRQs can be:
     *      rxIRQ from nonempty rxFIFO which requires to empty rxFIFO.
     *      txIRQ from empty txFIFO which requires to refill txFIFO.
     * - last interrupt is triggered by empty txFIFO. The last state is
     *   known by empty rxBuffer and txBuffer. If there is nothing to receive
     *   or send - both operations have been finished and interrupts can be
     *   disabled.
     */

    /* Data to send or read or expected to receive */
    if ((handle->txRemainingBytes) || (handle->rxRemainingBytes) || (handle->toReceiveCount))
    {
        /* Transmit or receive data */
        SPI_TransferHandleIRQInternal(base, handle);
        /* No data to send or read or receive. Transfer ends. Set txTrigger to 0 level and
         * enable txIRQ to confirm when txFIFO becomes empty */
        if ((!handle->txRemainingBytes) && (!handle->rxRemainingBytes) && (!handle->toReceiveCount))
        {
            base->FIFOTRIG = base->FIFOTRIG & (~SPI_FIFOTRIG_TXLVL_MASK);
            base->FIFOINTENSET |= SPI_FIFOINTENSET_TXLVL_MASK;
        }
        else
        {
            uint32_t rxRemainingCount = SPI_BYTES_TO_COUNT(handle->dataWidth, handle->rxRemainingBytes);
            /* If, there are no data to send or rxFIFO is already filled with necessary number of dummy data,
             * disable txIRQ. From this point only rxIRQ is used to receive data without any transmission */
            if ((!handle->txRemainingBytes) && (rxRemainingCount <= handle->toReceiveCount))
            {
                base->FIFOINTENCLR = SPI_FIFOINTENCLR_TXLVL_MASK;
            }
            /* Nothing to receive or transmit, but we still have pending data which are bellow rxLevel.
             * Cannot clear rxFIFO, txFIFO might be still active */
            if (rxRemainingCount == 0)
            {
                if ((handle->txRemainingBytes == 0) && (handle->toReceiveCount != 0) &&
                    (handle->toReceiveCount < SPI_FIFOTRIG_RXLVL_GET(base) + 1))
                {
                    base->FIFOTRIG =
                        (base->FIFOTRIG & (~SPI_FIFOTRIG_RXLVL_MASK)) | SPI_FIFOTRIG_RXLVL(handle->toReceiveCount - 1);
                }
            }
            /* Expected to receive less data than rxLevel value, we have to update rxLevel */
            else
            {
                if (rxRemainingCount < (SPI_FIFOTRIG_RXLVL_GET(base) + 1))
                {
                    base->FIFOTRIG =
                        (base->FIFOTRIG & (~SPI_FIFOTRIG_RXLVL_MASK)) | SPI_FIFOTRIG_RXLVL(rxRemainingCount - 1);
                }
            }
        }
    }
    else
    {
        /* Empty txFIFO is confirmed. Disable IRQs and restore triggers values */
        base->FIFOINTENCLR = SPI_FIFOINTENCLR_RXLVL_MASK | SPI_FIFOINTENCLR_TXLVL_MASK;
        base->FIFOTRIG = (base->FIFOTRIG & (~(SPI_FIFOTRIG_RXLVL_MASK | SPI_FIFOTRIG_RXLVL_MASK))) |
                         SPI_FIFOTRIG_RXLVL(handle->rxWatermark) | SPI_FIFOTRIG_TXLVL(handle->txWatermark);
        /* set idle state and call user callback */
        handle->state = kStatus_SPI_Idle;
        if (handle->callback)
        {
            (handle->callback)(base, handle, handle->state, handle->userData);
        }
    }
}

Have a great day,
Kerry

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