Posted on April 28, 2015 at 11:25SPI3 is configured as master readonly.
When the SPI is enabled then the clock can be monitored by an oscilloscope.
The Interrupt-handler stops SPI3 after having received 3 bytes. However the data are always Zero regardless of MISO is 1 or 0.
void SPI3_readonly_Config(void) { // SPI3 is Master readonly
/* available SPI3-Pins:
SPI3_SCK: PB3 (JTAG-conflict) use: PC10
SPI3_MISO PB4 (JTAG-conflict) use: PC11
SPI3_MOSI PB5 (JTAG-conflict) use: PC12, not used because readonly
SPI3_NSS PA15, not used
*/
GPIO_InitTypeDef GPIO_InitStructure;
SPI_InitTypeDef SPI_InitStructure;
NVIC_InitTypeDef NVIC_InitStructure;
/* Enable the SPI clock */
RCC_APB1PeriphClockCmd(RCC_APB1Periph_SPI3, ENABLE);
/* Enable GPIOC clock, do not use MOSI and NSS */
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOC, ENABLE);
/* Connect SPI pins to AF6, do not use MOSI */
GPIO_PinAFConfig(GPIOC, GPIO_PinSource10, GPIO_AF_SPI3);
GPIO_PinAFConfig(GPIOC, GPIO_PinSource11, GPIO_AF_SPI3);
/* SPI SCK pin configuration */
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_DOWN;
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;
GPIO_Init(GPIOC, &GPIO_InitStructure);
/* SPI MOSI pin configuration not used, because readonly */
/* SPI MISO pin configuration as input */
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_11;
GPIO_Init(GPIOC, &GPIO_InitStructure);
/* NSS pin not used */
/* SPI configuration ----------------------------------------*/
SPI_I2S_DeInit(SPI3);
SPI_InitStructure.SPI_Direction = SPI_Direction_2Lines_RxOnly;
SPI_InitStructure.SPI_DataSize = SPI_DataSize_8b;
SPI_InitStructure.SPI_CPOL = SPI_CPOL_Low;
SPI_InitStructure.SPI_CPHA = SPI_CPHA_1Edge;
SPI_InitStructure.SPI_NSS = SPI_NSS_Soft;
SPI_InitStructure.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_64;
SPI_InitStructure.SPI_FirstBit = SPI_FirstBit_MSB;
SPI_InitStructure.SPI_CRCPolynomial = 0;
SPI_InitStructure.SPI_Mode = SPI_Mode_Master;
SPI_Init(SPI3, &SPI_InitStructure);
/* Configure the SPI interrupt */
NVIC_InitStructure.NVIC_IRQChannel = SPI3_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);
/* Enable SPI_MASTER RXNE interrupt */
SPI_I2S_ITConfig(SPI3,SPI_I2S_IT_RXNE, ENABLE);
// SPI_Cmd(SPI3, ENABLE); do not enable SPI here
}
uint8_t SPI3values[3]={0};
uint32_t SPIindex = 0;
/* SPI3 Interrupt Handler */
void SPI3_IRQHandler(void) { // receive 3 bytes
if (SPI_I2S_GetITStatus(SPI3, SPI_I2S_IT_RXNE) == SET) {
SPI3values[SPIindex] = SPI3->DR; // content of array is always zeros
if(SPIindex > 1) {
/* disable SPI */
SPI3->CR1 &= 0xFFBF; // clear SPE Bit
....
/* stop SPI, disable SPI clock */
RCC_APB1PeriphClockCmd(RCC_APB1Periph_SPI3, DISABLE);
SPIindex = 0;
} else SPIindex++;
}
}
The clock configuration seems to be successful but what is wrong with the MISO-configuration?
