uint32_t config_usart3(void)
{

//=============================================================================
// USART3 Related configuration
//=============================================================================
// enable clock
RCC->APB1ENR |= RCC_APB1ENR_USART3EN;


// 1) Setting UE, amd M bits
USART3-> CR1 |= 0x2000; // UE = 1

// 2) Programming number of stop bits if needed


// 3) Enable DMA if needed


// 4) set the Baud Rate
// BAUD = fck / ( 8 * (2 - OVER8) * USARTDIV )
// fck = 42MHz,
// OVER8 = 0
// Choose BAUD = 115200
// then: USARTDIV = fck / ( 8 * (2 -OVER8) * BAUD = 22.75
// BRR = (22 << 4) | ( 0.75 * 16) = 364,
// or: BRR = fck / BAUD = 42MHz / 115200 = 364
USART3->BRR = 364;


// enable transmitter
USART3->CR1 |= USART_CR1_TE;

// enable receiver
USART3->CR1 |= USART_CR1_RE;

return 0;
}

uint8_t mem_read_gyro(USART_TypeDef *USART_ID )
{

int i=0; // loop var


//send read buffer to USART
for(i=0;i<=17281024;i++)
{
// check if TXE bit is set
while((!(USART_ID->SR & USART_SR_TXE)) );


USART_ID->DR = 0x5d;//mem_gyro_buf[i]; // sending a byte
// check if TC bit is set
while((!(USART_ID->SR & USART_SR_TC)) );

}



return 0;
}

//=============================================================================
// GPIOD configuration
//=============================================================================
// enable GPIOD clock
((RCC_TypeDef *)(RCC_BASE))->AHB1ENR |= RCC_AHB1ENR_GPIODEN;


// Alternate Function
((GPIO_TypeDef *)(GPIOD_BASE))->MODER |=
(GPIO_MODER_MODER9_1 | // Alternate Function, USART3_RX
GPIO_MODER_MODER8_1 | // Alternate Function, USART3_TX
GPIO_MODER_MODER11_1 | // Alternate Function, USART3_CTS
GPIO_MODER_MODER12_1 // Alternate Function, USART3_RTS
);

// Output type
GPIOD->OTYPER = 0;
//((GPIO_TypeDef *)(GPIOD_BASE))->OTYPER |= //0;// push-pull if 0
//(
//GPIO_OTYPER_OT_11 // Open-Drain, I2C1, SCL
////GPIO_OTYPER_OT_9 // OPen-Drain, I2C1, SDA
//);


// Speed type
((GPIO_TypeDef *)(GPIOD))->OSPEEDR |=
(GPIO_OSPEEDER_OSPEEDR8_1 | // USART3 TX 50 MHz
GPIO_OSPEEDER_OSPEEDR9_1 | // USART3 RX 50 MHz
GPIO_OSPEEDER_OSPEEDR11_1 | // USART3 CTS 50 MHz
GPIO_OSPEEDER_OSPEEDR12_1 // USART3 RTS 50 MHz
);


// Push/Pull for USART3
GPIOD->PUPDR = 0;
((GPIO_TypeDef *)(GPIOD_BASE))->PUPDR |=
(
GPIO_PUPDR_PUPDR8_0 | // Pull-Up, USART3 TX
GPIO_PUPDR_PUPDR9_0 | // Pull-Up, USART3 RX
GPIO_PUPDR_PUPDR11_0 | // Pull-Up, USART3 CTS
GPIO_PUPDR_PUPDR12_0 // Pull-Up, USART3 RTS
);


((GPIO_TypeDef *)(GPIOD_BASE))->AFR[1] |= (
(7 << ((8 - 8) << 2)) | // USART3 TX, AF7
(7 << ((9 - 8) << 2)) | // USART3 RX, AF7
(7 << ((11 - 8) << 2)) | // USART3 CTS, AF7
(7 << ((12 - 8) << 2)) // USART3 RTS, AF7
);

uint32_t config_usart3(void)
{

//=============================================================================
// USART3 Related configuration
//=============================================================================
// enable clock
RCC->APB1ENR |= RCC_APB1ENR_USART3EN;


// 1) Setting UE, amd M bits
USART3-> CR1 |= 0x2000; // UE = 1

// 2) Programming number of stop bits if needed


// 3) Enable DMA if needed


// 4) set the Baud Rate
// BAUD = fck / ( 8 * (2 - OVER8) * USARTDIV )
// fck = 42MHz,
// OVER8 = 0
// Choose BAUD = 115200
// then: USARTDIV = fck / ( 8 * (2 -OVER8) * BAUD = 22.75
// BRR = (22 << 4) | ( 0.75 * 16) = 364,
// or: BRR = fck / BAUD = 42MHz / 115200 = 364
USART3->BRR = 364;


// enable transmitter
USART3->CR1 |= USART_CR1_TE;

// enable receiver
USART3->CR1 |= USART_CR1_RE;

// enable CTS/RTS
USART3->CR3 |=
(
USART_CR3_CTSE |
USART_CR3_RTSE
);

return 0;
}

//=============================================================================
// GPIOD configuration
//=============================================================================
// enable GPIOD clock
((RCC_TypeDef *)(RCC_BASE))->AHB1ENR |= RCC_AHB1ENR_GPIODEN;


// Alternate Function
((GPIO_TypeDef *)(GPIOD_BASE))->MODER |=
(GPIO_MODER_MODER9_1 | // Alternate Function, USART3_RX
GPIO_MODER_MODER8_1 | // Alternate Function, USART3_TX
GPIO_MODER_MODER11_1 | // Alternate Function, USART3_CTS
GPIO_MODER_MODER12_1 // Alternate Function, USART3_RTS
);

// Output type
GPIOD->OTYPER = 0;



// Speed type
((GPIO_TypeDef *)(GPIOD))->OSPEEDR |=
(GPIO_OSPEEDER_OSPEEDR8_1 | // USART3 TX 50 MHz
GPIO_OSPEEDER_OSPEEDR9_1 | // USART3 RX 50 MHz
GPIO_OSPEEDER_OSPEEDR11_1 | // USART3 CTS 50 MHz
GPIO_OSPEEDER_OSPEEDR12_1 // USART3 RTS 50 MHz
);


// Push/Pull for USART3
GPIOD->PUPDR = 0;
((GPIO_TypeDef *)(GPIOD_BASE))->PUPDR |=
(
GPIO_PUPDR_PUPDR8_0 | // Pull-Up, USART3 TX
GPIO_PUPDR_PUPDR9_0 | // Pull-Up, USART3 RX
GPIO_PUPDR_PUPDR11_0 | // Pull-Up, USART3 CTS
GPIO_PUPDR_PUPDR12_0 // Pull-Up, USART3 RTS
);


((GPIO_TypeDef *)(GPIOD_BASE))->AFR[1] |= (
(7 << ((8 - 8) << 2)) | // USART3 TX, AF7
(7 << ((9 - 8) << 2)) | // USART3 RX, AF7
(7 << ((11 - 8) << 2)) | // USART3 CTS, AF7
(7 << ((12 - 8) << 2)) // USART3 RTS, AF7
);

uint8_t mem_read(USART_TypeDef *USART_ID )
{
uint32_t i=0; // loop var


//send read buffer to USART
for(i=0;i<=600000;i++)
{
// check if TXE bit is set
while((!(USART_ID->SR & USART_SR_TXE)) );

USART_ID->DR = 0x5d; // sending a byte

// check if TC bit is set
while((!(USART_ID->SR & USART_SR_TC)) );


}

return 0;
}uint8_t mem_read(USART_TypeDef *USART_ID )
{
uint32_t i=0; // loop var


//send read buffer to USART
for(i=0;i<=600000;i++)
{
// check if TXE bit is set
while((!(USART_ID->SR & USART_SR_TXE)) );

USART_ID->DR = 0x5d; // sending a byte

// check if TC bit is set
while((!(USART_ID->SR & USART_SR_TC)) );


}

return 0;
}