feat(spi): add transfer api with tx/rx buffer

Fixes #2205

Signed-off-by: Frederic Pillon <frederic.pillon@st.com>

Author: fpistm

libraries/SPI/src/SPI.cpp

@@ -163,7 +163,7 @@ void SPIClass::setClockDivider(uint8_t divider)
   */
 uint8_t SPIClass::transfer(uint8_t data, bool skipReceive)
 {
-  spi_transfer(&_spi, &data, sizeof(uint8_t), skipReceive);
+  spi_transfer(&_spi, &data, (!skipReceive) ? &data : NULL, sizeof(uint8_t));
   return data;
 }
 
@@ -184,7 +184,7 @@ uint16_t SPIClass::transfer16(uint16_t data, bool skipReceive)
     tmp = ((data & 0xff00) >> 8) | ((data & 0xff) << 8);
     data = tmp;
   }
-  spi_transfer(&_spi, (uint8_t *)&data, sizeof(uint16_t), skipReceive);
+  spi_transfer(&_spi, (uint8_t *)&data, (!skipReceive) ? (uint8_t *)&data : NULL, sizeof(uint16_t));
 
   if (_spiSettings.bitOrder) {
     tmp = ((data & 0xff00) >> 8) | ((data & 0xff) << 8);
@@ -206,11 +206,33 @@ uint16_t SPIClass::transfer16(uint16_t data, bool skipReceive)
   */
 void SPIClass::transfer(void *buf, size_t count, bool skipReceive)
 {
-  if ((count != 0) && (buf != NULL)) {
-    spi_transfer(&_spi, ((uint8_t *)buf), count, skipReceive);
+  spi_transfer(&_spi, (uint8_t *)buf, (!skipReceive) ? (uint8_t *)buf : NULL, count);
+
+}
+
+/**
+  * @brief  Transfer several bytes. One constant buffer used to send and
+  *         one to receive data.
+  *         begin() or beginTransaction() must be called at least once before.
+  * @param  tx_buf: array of Tx bytes that is filled by the user before starting
+  *                 the SPI transfer. If NULL, default dummy 0xFF bytes will be
+  *                 clocked out.
+  * @param  rx_buf: array of Rx bytes that will be filled by the slave during
+  *                 the SPI transfer. If NULL, the received data will be discarded.
+  * @param  count: number of bytes to send/receive.
+  */
+void SPIClass::transfer(const void *tx_buf, void *rx_buf, size_t count)
+{
+  if (tx_buf) {
+    spi_transfer(&_spi, ((const uint8_t *)tx_buf), ((uint8_t *)rx_buf), count);
+  } else {
+    uint8_t dummy_buf[count];
+    memset(dummy_buf, 0XFF, count);
+    spi_transfer(&_spi, dummy_buf, ((uint8_t *)rx_buf), count);
   }
 }
 
+
 /**
   * @brief  Not implemented.
   */

libraries/SPI/src/SPI.h

@@ -138,6 +138,11 @@ class SPIClass {
     uint16_t transfer16(uint16_t data, bool skipReceive = SPI_TRANSMITRECEIVE);
     void transfer(void *buf, size_t count, bool skipReceive = SPI_TRANSMITRECEIVE);
 
+    /* Expand SPI API
+     * https://github.com/arduino/ArduinoCore-API/discussions/189
+     */
+    void transfer(const void *tx_buf, void *rx_buf, size_t count);
+
     /* These methods are deprecated and kept for compatibility.
      * Use SPISettings with SPI.beginTransaction() to configure SPI parameters.
      */

libraries/SPI/src/utility/spi_com.c

@@ -500,17 +500,18 @@ void spi_deinit(spi_t *obj)
   * @brief This function is implemented by user to send/receive data over
   *         SPI interface
   * @param  obj : pointer to spi_t structure
-  * @param  buffer : tx data to send before reception
+  * @param  tx_buffer : tx data to send before reception
+  * @param  rx_buffer : rx data to receive if not numm
   * @param  len : length in byte of the data to send and receive
-  * @param  skipReceive: skip receiving data after transmit or not
   * @retval status of the send operation (0) in case of error
   */
-spi_status_e spi_transfer(spi_t *obj, uint8_t *buffer, uint16_t len, bool skipReceive)
+spi_status_e spi_transfer(spi_t *obj, const uint8_t *tx_buffer, uint8_t *rx_buffer,
+                          uint16_t len)
 {
   spi_status_e ret = SPI_OK;
   uint32_t tickstart, size = len;
   SPI_TypeDef *_SPI = obj->handle.Instance;
-  uint8_t *tx_buffer = buffer;
+  uint8_t *tx_buf = (uint8_t *)tx_buffer;
 
   if (len == 0) {
     ret = SPI_ERROR;
@@ -530,15 +531,15 @@ spi_status_e spi_transfer(spi_t *obj, uint8_t *buffer, uint16_t len, bool skipRe
 #else
       while (!LL_SPI_IsActiveFlag_TXE(_SPI));
 #endif
-      LL_SPI_TransmitData8(_SPI, *tx_buffer++);
+      LL_SPI_TransmitData8(_SPI, *tx_buf++);
 
-      if (!skipReceive) {
+      if (rx_buffer) {
 #if defined(SPI_SR_RXP)
         while (!LL_SPI_IsActiveFlag_RXP(_SPI));
 #else
         while (!LL_SPI_IsActiveFlag_RXNE(_SPI));
 #endif
-        *buffer++ = LL_SPI_ReceiveData8(_SPI);
+        *rx_buffer++ = LL_SPI_ReceiveData8(_SPI);
       }
       if ((SPI_TRANSFER_TIMEOUT != HAL_MAX_DELAY) &&
           (HAL_GetTick() - tickstart >= SPI_TRANSFER_TIMEOUT)) {

libraries/SPI/src/utility/spi_com.h

@@ -110,7 +110,7 @@ typedef enum {
 /* Exported functions ------------------------------------------------------- */
 void spi_init(spi_t *obj, uint32_t speed, SPIMode mode, uint8_t msb);
 void spi_deinit(spi_t *obj);
-spi_status_e spi_transfer(spi_t *obj, uint8_t *buffer, uint16_t len, bool skipReceive);
+spi_status_e spi_transfer(spi_t *obj, const uint8_t *tx_buffer, uint8_t *rx_buffer, uint16_t len);
 uint32_t spi_getClkFreq(spi_t *obj);
 
 #ifdef __cplusplus