Issue using UART with STM32F0Discovery and Fingerprint Scanner - stm32

Question

I am currently working on a project that involves the STM32f0Discovery board and this fingerprint scanner, which uses UART communication. To initialize the UART, I do the following:
void init_uart(void){
GPIO_InitTypeDef GPIO_InitStructure;
USART_InitTypeDef USART_InitStructure;
USART_InitStructure.USART_BaudRate = 9600;
USART_InitStructure.USART_WordLength = USART_WordLength_8b;
USART_InitStructure.USART_StopBits = USART_StopBits_1;
USART_InitStructure.USART_Parity = USART_Parity_No;
USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;
RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOA, ENABLE);
RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE);
GPIO_PinAFConfig(GPIOA, GPIO_PinSource9, GPIO_AF_1);
GPIO_PinAFConfig(GPIOA, GPIO_PinSource10, GPIO_AF_1);
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9 | GPIO_Pin_10;
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_UP;
GPIO_Init(GPIOA, &GPIO_InitStructure);
USART_Init(USART1, &USART_InitStructure);
USART_Cmd(USART1, ENABLE);
USART_ITConfig(USART1, USART_IT_RXNE, ENABLE);
}
Then to send/receive a byte I do the following:
void writechar(char c) {
while((USART1 -> ISR & USART_ISR_TC) != USART_ISR_TC);
USART1 -> TDR = c;
}
char readchar(void) {
return USART_ReceiveData(USART1);
}
To test this, I sent the OPEN command byte-by-byte through a for-loop, then the LEN-ON command the same method, which has no results. When reading for an ACK after the OPEN command, the results read are just an empty array of char bytes.
So, my question is, is my initialization the error? Or is the error in the reading/writing? Or could it be something else altogether?

Answer 1

Are you getting the ACK response ? If you are not then there is probably a configuration or wiring problem. I would suggest you try connecting the serial pins to a serial-usb converter
(FTDI such as this :Click here)
and use an app like Putty or YAT to send commands (ACK) to and from your stm. Try using the same configuration the scanner has if that doesn't work its a problem with your config if it does work its a problem scanner side.