cpu/stm32f1: improve SPI driver speed

cpu/stm32f1/include/periph_cpu.h

@@ -40,6 +40,13 @@ extern "C" {
  */
 #define TIMER_MAXVAL        (0xffff)
 
+/**
+ * @brief declare needed generic SPI functions
+ * @{
+ */
+#undef PERIPH_SPI_NEEDS_TRANSFER_BYTES
+#define PERIPH_SPI_NEEDS_TRANSFER_BYTE
+
 /**
  * @brief   Generate GPIO mode bitfields
  *

cpu/stm32f1/periph/spi.c

@@ -183,8 +183,9 @@ int spi_release(spi_t dev)
     return 0;
 }
 
-int spi_transfer_byte(spi_t dev, char out, char *in)
+int spi_transfer_bytes(spi_t dev, char *out, char *in, unsigned int length)
 {
+
     SPI_TypeDef *spi;
     int transferred = 0;
 
@@ -210,27 +211,34 @@ int spi_transfer_byte(spi_t dev, char out, char *in)
             return -1;
     }
 
-    while (!(spi->SR & SPI_SR_TXE)) {}
-    spi->DR = out;
-    transferred++;
-
-    while (!(spi->SR & SPI_SR_RXNE)) {}
-    if (in != NULL) {
-        *in = spi->DR;
-        transferred++;
+    if(!in){
+        for (unsigned i = 0; i < length; i++) {
+            while (!(spi->SR & SPI_SR_TXE)) {}
+            spi->DR = (uint8_t)out[i];
+        }
+        /* SPI busy */
+        while ((spi->SR & SPI_SR_BSY)) {}
+        spi->DR;
+    }
+    else if(!out) {
+        for (unsigned i = 0; i < length; i++) {
+            spi->DR = 0;
+            while (!(spi->SR & SPI_SR_RXNE)) {}
+            in[i] = (char)spi->DR;
+        }
     }
     else {
-        spi->DR;
+        for (unsigned i = 0; i < length; i++) {
+            while (!(spi->SR & SPI_SR_TXE)) {}
+            spi->DR = out[i];
+            while (!(spi->SR & SPI_SR_RXNE)) {}
+            in[i] = (char)spi->DR;
+        }
     }
 
-    /* SPI busy */
-    while ((spi->SR & 0x80)) {}
 #if ENABLE_DEBUG
     if (in != NULL) {
-        DEBUG("\nout: %x in: %x transferred: %x\n", out, *in, transferred);
-    }
-    else {
-        DEBUG("\nout: %x in: was nullPointer transferred: %x\n", out, transferred);
+        DEBUG("\nSPI: transferred %i Bytes\n", length);
     }
 #endif /*ENABLE_DEBUG */
 
@@ -275,6 +283,7 @@ void spi_poweroff(spi_t dev)
     switch (dev) {
 #if SPI_0_EN
         case SPI_0:
+            while ((SPI_0_DEV->SR & SPI_SR_BSY)) {}
             SPI_0_DEV->CR1 &= ~(SPI_CR1_SPE);   /* turn SPI peripheral off */
             SPI_0_CLKDIS();
             break;
@@ -282,6 +291,7 @@ void spi_poweroff(spi_t dev)
 
 #if SPI_1_EN
         case SPI_1:
+            while ((SPI_1_DEV->SR & SPI_SR_BSY)) {}
             SPI_1_DEV->CR1 &= ~(SPI_CR1_SPE);   /* turn SPI peripheral off */
             SPI_1_CLKDIS();
             break;
@@ -289,6 +299,7 @@ void spi_poweroff(spi_t dev)
 
 #if SPI_2_EN
         case SPI_2:
+            while ((SPI_2_DEV->SR & SPI_SR_BSY)) {}
             SPI_2_DEV->CR1 &= ~(SPI_CR1_SPE);   /* turn SPI peripheral off */
             SPI_2_CLKDIS();
             break;