The primary goal of this laboratory exercise is to gain hands$-$on experience in configuring and using DMA to transfer data between peripheral modules and memory. Additionally, you will explore essential practices in managing C projects, which involve multiple $\text{'}.$c$\text{'}$ and $\text{'}.$h$\text{'}$ files. This knowledge is crucial for ensuring the system's maintainability and scalability, as well as for supporting effective collaboration. You are provided with a sample project, Lab$8\_$Project$\_$Template, which integrates the Lab $3$ project and the UART$\_$Terminal sample project. This project implements a counter that increments by one every second using the general$-$purpose timer TIM$2$ in output compare toggle mode. The counter value is converted into a character string stored in a character array named 'string,$\text{'}$ and displayed on a PC serial terminal through the USART$2$ TX port. Essentially, you will see the counter value automatically increment by one and be displayed on the serial terminal every second. In this sample project, the character string representing the counter value is transferred from the memory array 'string' to the USART$2$ Transmit Data Register $($TDR$)$ via software $($i$.$e$.,$ the processor$).$ Your task is to modify the project so this array of data will be transferred using DMA instead of software. You will need to identify the DMA channel that is mapped to USART$2$ TX and set up the DMA module and channel to transfer data from memory to USART$2$ TX$.$ The DMA transfer should be initiated whenever the counter value is updated. Hint: You can enable DMA transfer in the TIM$2\_$IRQHandler after the counter is incremented and converted into a new string. Once the transfer is complete, an interrupt associated with the DMA channel can be triggered to disable the DMA channel. The channel will be re$-$enabled when the counter is updated, i$.$e$.,$ when the TIM$2$ interrupt is triggered again. You are required to add a $$DMA$.$c$$ and a $$DMA$.$h$$ file to the project and place the relevant DMA variables and function declarations and definitions into these two files.

main.c

#include $"$stm$32$l$476$xx$.$h$"$

#include "LED.h$"$

#include "USART$2.$h$"$

int main$($void$)\{$

char msg$[]=$ "Welcome! Please input a $5-$digit number and then press Enter:

$\backslash$r$"$;

int i$=0$;

$//$ Configure PA$5$ to serve as an output pin, used for controlling the on$-$board LED $($LD$2).$

configure$\_$LED$\_$pin$()$;

$//$ Initialize USART$2$ for communication with a PC via serial terminal.

$//$ Configuration details:

$//-$ Data format: $8$ data bits, no parity, $1$ start bit, and $1$ stop bit

$//-$ Baud rate: $9600$

$//-$ Enable RXNE interrupt to trigger when a new character is received, allowing for responsive character echo.

USART$2\_$Init$()$;

$//$ Configuring DMA$1$ Channel $6$ as the USART$2$ RX channel.

DMA$1\_$Channel$6\_$Configruation$()$;

$//$ Loop to send the welcome message character by character when the system restarts.

while$($msg$[$i$]!=\text{'}\backslash 0\text{'})\{$

$//$ Wait until the TXE $($Transmit Data Register Empty$)$ flag is set, indicating readiness to send the next character.

while $(!($USART$2->$ISR & USART$\_$ISR$\_$TXE$))$;

$//$ Send the current character and automatically clear the TXE flag by writing to USART$\_$TDR$.$

$//$ increment i after sending the current character

USART$2->$TDR $=$ msg$[$i$++]$;

$\}$

$//$ Enter an infinite loop to maintain the program's operation.

while $(1)\{$

$\}$

$\}$

DMA$1.$c

#include "DMA$1.$h$"$

#include

$//$ The memory buffer array stores the data received from the USART$2$ receiver.

volatile uint$8\_$t Buffer$\_$R$[6]$;

$//$ Configuring DMA$1$ Channel $6$ as the USART$2$ RX channel.

void DMA$1\_$Channel$6\_$Configruation$($void$)$

$\{$

$//$ Enable the DMA$1$ clock in the AHB$1$ peripheral clock enable register

RCC$->$AHB$1$ENR $|=$ RCC$\_$AHB$1$ENR$\_$DMA$1$EN;

$//$ Map USART$2$ RX to DMA$1$ Channel $6$

$//$ C$6$S$[3$:$0]=\text{'}0010\text{'}$

DMA$1\_$CSELR$->$CSELR &$=$ ~DMA$\_$CSELR$\_$C$6$S;

DMA$1\_$CSELR$->$CSELR $|=0$b;

$//$ Disabling DMA$1$ Channel $6$ to allow configuration

DMA$1\_$Channel$6->$CCR &$=$ ~DMA$\_$CCR$\_$EN;

$//$ Peripheral data size for each DMA transfer: $\text{'}00\text{'}$ equals $8$ bits.

DMA$1\_$Channel$6->$CCR &$=$ ~DMA$\_$CCR$\_$PSIZE;

$//$ Memory data size for each DMA transfer: $\text{'}00\text{'}$ equals $8$ bits.

DMA$1\_$Channel$6->$CCR &$=$ ~DMA$\_$CCR$\_$MSIZE;

$//$ Disable peripheral increment mode $($no incrementation after each transfer$)$

DMA$1\_$Channel$6->$CCR &$=$ ~DMA$\_$CCR$\_$PINC;

$//$ Enable memory increment mode $($memory address incremented by $1$ after each transfer$)$

DMA$1\_$Channel$6->$CCR $|=$ DMA$\_$CCR$\_$MINC;

$//$ Configure transfer direction: $\text{'}0\text{'}$ indicates from peripheral to memory.

DMA$1\_$Channel$6->$CCR &$=$ ~DMA$\_$CCR$\_$DIR;

$//$ Number of data to transfer

DMA$1\_$Channel$6->$CNDTR $=6$;

$//$ Peripheral address: the address of the USART$2$ RDR register

DMA$1\_$Channel$6->$CPAR $=($uint$32\_$t$)$&$($USART$2->$RDR$)$;

$//$ Memory address: the address of the memory buffer array

DMA$1\_$Channel$6->$CMAR $=($uint$32\_$t$)$Buffer$\_$R;

$//$ Enable Circular Mode for DMA$1$ Channel $6$

DMA$1\_$Channel$6->$CCR $|=$ DMA$\_$CCR$\_$CIRC;

$//$ Enable the transfer complete interrupt for DMA$1$ Channel $6$

DMA$1\_$Channel$6->$CCR $|=$ DMA$\_$CCR$\_$TCIE;