Atmel provided hardware specifics.

Demo/Common/drivers/Atmel/at91lib/peripherals/ssc/ssc.c

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+/* ----------------------------------------------------------------------------
+ *         ATMEL Microcontroller Software Support 
+ * ----------------------------------------------------------------------------
+ * Copyright (c) 2008, Atmel Corporation
+ *
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * - Redistributions of source code must retain the above copyright notice,
+ * this list of conditions and the disclaimer below.
+ *
+ * Atmel's name may not be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * DISCLAIMER: THIS SOFTWARE IS PROVIDED BY ATMEL "AS IS" AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT ARE
+ * DISCLAIMED. IN NO EVENT SHALL ATMEL BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
+ * OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
+ * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ * ----------------------------------------------------------------------------
+ */
+
+//------------------------------------------------------------------------------
+//         Headers
+//------------------------------------------------------------------------------
+
+#include "ssc.h"
+#include <utility/trace.h>
+
+//------------------------------------------------------------------------------
+//         Exported functions
+//------------------------------------------------------------------------------
+//------------------------------------------------------------------------------
+/// Configures a SSC peripheral. If the divided clock is not used, the master
+/// clock frequency can be set to 0.
+/// \note The emitter and transmitter are disabled by this function.
+/// \param ssc  Pointer to an AT91S_SSC instance.
+/// \param id  Peripheral ID of the SSC.
+//------------------------------------------------------------------------------
+void SSC_Configure(AT91S_SSC *ssc,
+                          unsigned int id,
+                          unsigned int bitRate,
+                          unsigned int masterClock)
+{
+    // Enable SSC peripheral clock
+    AT91C_BASE_PMC->PMC_PCER = 1 << id;
+
+    // Reset, disable receiver & transmitter
+    ssc->SSC_CR = AT91C_SSC_RXDIS | AT91C_SSC_TXDIS | AT91C_SSC_SWRST;
+    ssc->SSC_PTCR = AT91C_PDC_RXTDIS | AT91C_PDC_TXTDIS;
+
+    // Configure clock frequency
+    if (bitRate != 0) {
+    
+        ssc->SSC_CMR = masterClock / (2 * bitRate);
+    }
+    else {
+
+        ssc->SSC_CMR = 0;
+    }
+}
+
+//------------------------------------------------------------------------------
+/// Configures the transmitter of a SSC peripheral. Several macros can be used
+/// to compute the values of the Transmit Clock Mode Register (TCMR) and the
+/// Transmit Frame Mode Register (TFMR) (see "SSC configuration macros").
+/// \param ssc  Pointer to a AT91S_SSC instance.
+/// \param tcmr  Transmit Clock Mode Register value.
+/// \param tfmr  Transmit Frame Mode Register value.
+//------------------------------------------------------------------------------
+void SSC_ConfigureTransmitter(AT91S_SSC *ssc,
+                                     unsigned int tcmr,
+                                     unsigned int tfmr)
+{
+    ssc->SSC_TCMR = tcmr;
+    ssc->SSC_TFMR = tfmr;
+}
+
+//------------------------------------------------------------------------------
+/// Configures the receiver of a SSC peripheral. Several macros can be used
+/// to compute the values of the Receive Clock Mode Register (TCMR) and the
+/// Receive Frame Mode Register (TFMR) (see "SSC configuration macros").
+/// \param ssc  Pointer to a AT91S_SSC instance.
+/// \param rcmr  Receive Clock Mode Register value.
+/// \param rfmr  Receive Frame Mode Register value.
+//------------------------------------------------------------------------------
+void SSC_ConfigureReceiver(AT91S_SSC *ssc,
+                                  unsigned int rcmr,
+                                  unsigned int rfmr)
+{
+    ssc->SSC_RCMR = rcmr;
+    ssc->SSC_RFMR = rfmr;
+}
+
+//------------------------------------------------------------------------------
+/// Enables the transmitter of a SSC peripheral.
+/// \param ssc  Pointer to an AT91S_SSC instance.
+//------------------------------------------------------------------------------
+void SSC_EnableTransmitter(AT91S_SSC *ssc)
+{
+    ssc->SSC_CR = AT91C_SSC_TXEN;
+}
+
+//------------------------------------------------------------------------------
+/// Disables the transmitter of a SSC peripheral.
+/// \param ssc  Pointer to an AT91S_SSC instance.
+//------------------------------------------------------------------------------
+void SSC_DisableTransmitter(AT91S_SSC *ssc)
+{
+    ssc->SSC_CR = AT91C_SSC_TXDIS;
+}
+
+//------------------------------------------------------------------------------
+/// Enables the receiver of a SSC peripheral.
+/// \param ssc  Pointer to an AT91S_SSC instance.
+//------------------------------------------------------------------------------
+void SSC_EnableReceiver(AT91S_SSC *ssc)
+{
+    ssc->SSC_CR = AT91C_SSC_RXEN;
+}
+
+//------------------------------------------------------------------------------
+/// Disables the receiver of a SSC peripheral.
+/// \param ssc  Pointer to an AT91S_SSC instance.
+//------------------------------------------------------------------------------
+void SSC_DisableReceiver(AT91S_SSC *ssc)
+{
+    ssc->SSC_CR = AT91C_SSC_RXDIS;
+}
+
+//------------------------------------------------------------------------------
+/// Enables one or more interrupt sources of a SSC peripheral.
+/// \param ssc  Pointer to an AT91S_SSC instance.
+/// \param sources  Interrupt sources to enable.
+//------------------------------------------------------------------------------
+void SSC_EnableInterrupts(AT91S_SSC *ssc, unsigned int sources)
+{
+    ssc->SSC_IER = sources;
+}
+
+//------------------------------------------------------------------------------
+/// Disables one or more interrupt sources of a SSC peripheral.
+/// \param ssc  Pointer to an AT91S_SSC instance.
+/// \param sources  Interrupt source to disable.
+//------------------------------------------------------------------------------
+void SSC_DisableInterrupts(AT91S_SSC *ssc, unsigned int sources)
+{
+    ssc->SSC_IDR = sources;
+}
+
+//------------------------------------------------------------------------------
+/// Sends one data frame through a SSC peripheral. If another frame is currently
+/// being sent, this function waits for the previous transfer to complete.
+/// \param ssc  Pointer to an AT91S_SSC instance.
+/// \param frame  Data frame to send.
+//------------------------------------------------------------------------------
+void SSC_Write(AT91S_SSC *ssc, unsigned int frame)
+{
+    while ((ssc->SSC_SR & AT91C_SSC_TXRDY) == 0);
+    ssc->SSC_THR = frame;
+}
+
+//------------------------------------------------------------------------------
+/// Sends the contents of a data buffer a SSC peripheral, using the PDC. Returns
+/// true if the buffer has been queued for transmission; otherwise returns
+/// false.
+/// \param ssc  Pointer to an AT91S_SSC instance.
+/// \param buffer  Data buffer to send.
+/// \param length  Size of the data buffer.
+//------------------------------------------------------------------------------
+unsigned char SSC_WriteBuffer(AT91S_SSC *ssc,
+                                     void *buffer,
+                                     unsigned int length)
+{
+    // Check if first bank is free
+    if (ssc->SSC_TCR == 0) {
+
+        ssc->SSC_TPR = (unsigned int) buffer;
+        ssc->SSC_TCR = length;
+        ssc->SSC_PTCR = AT91C_PDC_TXTEN;
+        return 1;
+    }
+    // Check if second bank is free
+    else if (ssc->SSC_TNCR == 0) {
+
+        ssc->SSC_TNPR = (unsigned int) buffer;
+        ssc->SSC_TNCR = length;
+        return 1;
+    }
+      
+    // No free banks
+    return 0;
+}
+
+//------------------------------------------------------------------------------
+/// Waits until one frame is received on a SSC peripheral, and returns it.
+/// \param ssc  Pointer to an AT91S_SSC instance.
+//------------------------------------------------------------------------------
+unsigned int SSC_Read(AT91S_SSC *ssc)
+{
+    while ((ssc->SSC_SR & AT91C_SSC_RXRDY) == 0);
+    return ssc->SSC_RHR;
+}
+
+//------------------------------------------------------------------------------
+/// Reads data coming from a SSC peripheral receiver and stores it into the
+/// provided buffer. Returns true if the buffer has been queued for reception;
+/// otherwise returns false.
+/// \param ssc  Pointer to an AT91S_SSC instance.
+/// \param buffer  Data buffer used for reception.
+/// \param length  Size in bytes of the data buffer.
+//------------------------------------------------------------------------------
+unsigned char SSC_ReadBuffer(AT91S_SSC *ssc,
+                                    void *buffer,
+                                    unsigned int length)
+{
+    // Check if the first bank is free
+    if (ssc->SSC_RCR == 0) {
+
+        ssc->SSC_RPR = (unsigned int) buffer;
+        ssc->SSC_RCR = length;
+        ssc->SSC_PTCR = AT91C_PDC_RXTEN;
+        return 1;
+    }
+    // Check if second bank is free
+    else if (ssc->SSC_RNCR == 0) {
+
+        ssc->SSC_RNPR = (unsigned int) buffer;
+        ssc->SSC_RNCR = length;
+        return 1;
+    }
+
+    // No free bank
+    return 0;
+}
+