Nuts and Volts - March 2018

n SCREENSHOT 8. Like the entries in Screenshot 7, these SPI settings will be turned into SPI portal configuration code by STMCube32MX.

/* SPI1 init function */
static void MX_SPI1_Init(void)
{
  /* SPI1 parameter configuration*/
  hspi1.Instance = SPI1;
  hspi1.Init.Mode = SPI_MODE_MASTER;
  hspi1.Init.Direction = SPI_DIRECTION_1LINE;
  hspi1.Init.DataSize = SPI_DATASIZE_8BIT;
  hspi1.Init.CLKPolarity = SPI_POLARITY_LOW;
  hspi1.Init.CLKPhase = SPI_PHASE_1EDGE;
  hspi1.Init.NSS = SPI_NSS_SOFT;
 hspi1.Init.BaudRatePrescaler = SPI_
 BAUDRATEPRESCALER_16;
 hspi1.Init.FirstBit = SPI_FIRSTBIT_MSB;
 hspi1.Init.TIMode = SPI_TIMODE_DISABLE;
 hspi1.Init.CRCCalculation = SPI_CRCCALCULATION_
 DISABLE;
 hspi1.Init.CRCPolynomial = 7;
 hspi1.Init.CRCLength = SPI_CRC_LENGTH_DATASIZE;
 hspi1.Init.NSSPMode = SPI_NSS_PULSE_DISABLE;
 if (HAL_SPI_Init(&hspi1) != HAL_OK)
 {
 _Error_Handler(__FILE__, __LINE__);
 }
 }
{
 txBite = command;
 clrDC;  // command mode
 clrCS;  // chip selected
 HAL_SPI_Transmit(&hspi1,&txBite,1,1000);
 setCS;  // deselect chip
}
//***********************************************
//* LCD Write Data
//***********************************************
void writeData(uint8_t data)
{
 txBite = data;
 setDC;  // data mode
 clrCS;  // chip selected
 HAL_SPI_Transmit(&hspi1,&txBite,1,1000);
 setCS;  // deselect chip

Again, the SPI init code is self-commenting. You can alter the final code by simply following the current definition backwards to the origin of all the definitions for a particular structure entry. For instance, if you trace back the Note that there is no read data command. That’s because the CFAL9664B-F-B1-CB doesn’t allow any LCD read operations in SPI mode. You can get a list of all the available STM32F030R8T6 HAL functions by clicking on the Functions tab in the Keil Project window. If you’re curious as to “how did they do that,” you can follow the trail backwards from the HAL function to the low-level calls in the Keil uVision IDE (integrated development environment).

SPI_BAUDRATEPRESCALER_XXX alias, you’ll find this: If you’re wondering where the SPI initialization code is, STMCube32MX put it into the project source automatically. Let’s take a look at it:

/** @defgroup SPI_BaudRate_Prescaler SPI BaudRate
Prescaler
 @{
  */
#define SPI_BAUDRATEPRESCALER_2 (0x00000000U)
#define SPI_BAUDRATEPRESCALER_4 (SPI_CR1_BR_0)
#define SPI_BAUDRATEPRESCALER_8 (SPI_CR1_BR_1)
#define SPI_BAUDRATEPRESCALER_16  (SPI_CR1_BR_1 |
SPI_CR1_BR_0)
#define SPI_BAUDRATEPRESCALER_32  (SPI_CR1_BR_2)
#define SPI_BAUDRATEPRESCALER_64  (SPI_CR1_BR_2 |
SPI_CR1_BR_0)
#define SPI_BAUDRATEPRESCALER_128 (SPI_CR1_BR_2 |
SPI_CR1_BR_1)
#define SPI_BAUDRATEPRESCALER_256 (SPI_CR1_BR_2 |
SPI_CR1_BR_1 | SPI_CR1_BR_0)

So, instead of running another spin of the STMCube32MX configurator to change the SPI_ BAUDRATEPRESCALER_XXX value, you can simply change the prescaler value manually in the generated source code.