Use slightly flatter directory structure since some developers did not

like too many folders.
Extracted code from some files into separate files to fit with the new
layout.

src/drivers/bus_spi.c

@@ -0,0 +1,101 @@
+#include "board.h"
+
+// SPI2 Driver
+// PB15     28      SPI2_MOSI
+// PB14     27      SPI2_MISO
+// PB13     26      SPI2_SCK
+// PB12     25      SPI2_NSS
+
+static bool spiTest(void);
+
+bool spiInit(void)
+{
+    gpio_config_t gpio;
+    SPI_InitTypeDef spi;
+
+    // Enable SPI2 clock
+    RCC_APB1PeriphClockCmd(RCC_APB1Periph_SPI2, ENABLE);
+    RCC_APB1PeriphResetCmd(RCC_APB1Periph_SPI2, ENABLE);
+
+    // MOSI + SCK as output
+    gpio.mode = Mode_AF_PP;
+    gpio.pin = Pin_13 | Pin_15;
+    gpio.speed = Speed_50MHz;
+    gpioInit(GPIOB, &gpio);
+    // MISO as input
+    gpio.pin = Pin_14;
+    gpio.mode = Mode_IN_FLOATING;
+    gpioInit(GPIOB, &gpio);
+    // NSS as gpio slave select
+    gpio.pin = Pin_12;
+    gpio.mode = Mode_Out_PP;
+    gpioInit(GPIOB, &gpio);
+
+    // Init SPI2 hardware
+    SPI_I2S_DeInit(SPI2);
+    spi.SPI_Mode = SPI_Mode_Master;
+    spi.SPI_Direction = SPI_Direction_2Lines_FullDuplex;
+    spi.SPI_DataSize = SPI_DataSize_8b;
+    spi.SPI_NSS = SPI_NSS_Soft;
+    spi.SPI_FirstBit = SPI_FirstBit_MSB;
+    spi.SPI_CRCPolynomial = 7;
+    spi.SPI_CPOL = SPI_CPOL_High;
+    spi.SPI_CPHA = SPI_CPHA_2Edge;
+    spi.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_8;
+    SPI_Init(SPI2, &spi);
+    SPI_Cmd(SPI2, ENABLE);
+
+    return spiTest();
+}
+
+void spiSelect(bool select)
+{
+    if (select) {
+        digitalLo(GPIOB, Pin_12);
+    } else {
+        digitalHi(GPIOB, Pin_12);
+    }
+}
+
+uint8_t spiTransferByte(uint8_t in)
+{
+    uint8_t rx;
+    SPI2->DR;
+    SPI2->DR = in;
+    while (!(SPI2->SR & SPI_I2S_FLAG_RXNE));
+    rx = SPI2->DR;
+    while (!(SPI2->SR & SPI_I2S_FLAG_TXE));
+    while (SPI2->SR & SPI_I2S_FLAG_BSY);
+    return rx;
+}
+
+bool spiTransfer(uint8_t *out, uint8_t *in, int len)
+{
+    uint8_t b;
+    SPI2->DR;
+    while (len--) {
+        b = in ? *(in++) : 0xFF;
+        while (SPI_I2S_GetFlagStatus(SPI2, SPI_I2S_FLAG_TXE) == RESET);
+        SPI_I2S_SendData(SPI2, b);
+        while (SPI_I2S_GetFlagStatus(SPI2, SPI_I2S_FLAG_RXNE) == RESET);
+        b = SPI_I2S_ReceiveData(SPI2);
+        if (out)
+            *(out++) = b;
+    }
+
+    return true;
+}
+
+static bool spiTest(void)
+{
+    uint8_t out[] = { 0x9F, 0, 0, 0 };
+    uint8_t in[4];
+
+    spiSelect(true);
+    spiTransfer(in, out, sizeof(out));
+    spiSelect(false);
+    if (in[1] == 0xEF)
+        return true;
+
+    return false;
+}