How to pass string/array to function correctly? (stm32) - arrays

Question

I'm not first and not last I mean)
And it's one more question about waring: assignment makes pointer from integer without a cast.
I've already read this and this and this and this and this and more and more.
I have NUCLEO-F070RB-STM32 devkit. And I want to send different messages on PC for debugging.
I use this construction:
uint8_t greeting[] = "Welcome to first circle of hell\n";
HAL_UART_Transmit(&huart2, greeting, sizeof(greeting)-1, 30);
//"sizeof(greeting)-1" cut "\0" from string
Here is a description:
/**
* #brief Send an amount of data in blocking mode.
* #note When UART parity is not enabled (PCE = 0), and Word Length is configured to 9 bits (M1-M0 = 01),
* the sent data is handled as a set of u16. In this case, Size must indicate the number
* of u16 provided through pData.
* #note When UART parity is not enabled (PCE = 0), and Word Length is configured to 9 bits (M1-M0 = 01),
* address of user data buffer containing data to be sent, should be aligned on a half word frontier (16 bits)
* (as sent data will be handled using u16 pointer cast). Depending on compilation chain,
* use of specific alignment compilation directives or pragmas might be required
* to ensure proper alignment for pData.
* #param huart UART handle.
* #param pData Pointer to data buffer (u8 or u16 data elements).
* #param Size Amount of data elements (u8 or u16) to be sent.
* #param Timeout Timeout duration.
* #retval HAL status
*/
And all work perfectly.
But I want different message. I'm a good programmer.
uint8_t greeting[] = "Welcome to first circle of hell\n";
uint8_t str[] = "just for UART\r\n";
void send_to_uart (uint8_t);
void send_to_uart (uint8_t it_will_be_send)
{
HAL_UART_Transmit(&huart2, it_will_be_send, sizeof(it_will_be_send)-1, 30);
}
int main(void)
{
send_to_uart(greeting);
wile (1)
{
send_to_uart(str);
}
}
And I have a warning and have no data on my screen.
Bad bad bad programmer!
I understand that devil in pointers.
But can you explain slowly step by step for all newbies like me:
How to pass ...n arrays to functions. PLEEEAASEEE
P.S.
/* USER CODE BEGIN 0 */
void send_to_uart (uint8_t);
void send_to_uart (uint8_t it_will_be_send)
{
HAL_UART_Transmit(&huart2, it_will_be_send, sizeof(it_will_be_send)-1, 30);
}
/* USER CODE END 0 */
/**
* #brief The application entry point.
* #retval int
*/
int main(void)
{
/* USER CODE BEGIN 1 */
/* USER CODE BEGIN WHILE */
uint8_t greeting[] = "\nWelcome to first circle of hell\n";
uint8_t some_string[] = "some string to UART\r\n";
send_to_uart(greeting);
HAL_UART_Transmit(&huart2, greeting, sizeof(greeting)-1, 30);
while (1)
{
HAL_UART_Transmit(&huart2, "\nHAL some string to UART\n" , 25, 30);
send_to_uart(some_string);
HAL_UART_Transmit(&huart2, some_string, sizeof(some_string)-1, 30);
/* USER CODE END WHILE */
/* USER CODE BEGIN 3 */
}
/* USER CODE END 3 */
}
make -j4 all
arm-none-eabi-gcc "../Core/Src/main.c" -mcpu=cortex-m0 -std=gnu11 -g3 -DDEBUG -DUSE_HAL_DRIVER -DSTM32F070xB -c -I../Core/Inc -I../Drivers/STM32F0xx_HAL_Driver/Inc -I../Drivers/STM32F0xx_HAL_Driver/Inc/Legacy -I../Drivers/CMSIS/Device/ST/STM32F0xx/Include -I../Drivers/CMSIS/Include -O0 -ffunction-sections -fdata-sections -Wall -fstack-usage -MMD -MP -MF"Core/Src/main.d" -MT"Core/Src/main.o" --specs=nano.specs -mfloat-abi=soft -mthumb -o "Core/Src/main.o"
../Core/Src/main.c: In function 'send_to_uart':
../Core/Src/main.c:67:29: warning: passing argument 2 of 'HAL_UART_Transmit' makes pointer from integer without a cast [-Wint-conversion]
67 | HAL_UART_Transmit(&huart2, it_will_be_send, sizeof(it_will_be_send)-1, 30);
| ^~~~~~~~~~~~~~~
| |
| uint8_t {aka unsigned char}
In file included from ../Core/Inc/stm32f0xx_hal_conf.h:288,
from ../Drivers/STM32F0xx_HAL_Driver/Inc/stm32f0xx_hal.h:30,
from ../Core/Inc/main.h:31,
from ../Core/Src/main.c:21:
../Drivers/STM32F0xx_HAL_Driver/Inc/stm32f0xx_hal_uart.h:1491:73: note: expected 'uint8_t *' {aka 'unsigned char *'} but argument is of type 'uint8_t' {aka 'unsigned char'}
1491 | HAL_StatusTypeDef HAL_UART_Transmit(UART_HandleTypeDef *huart, uint8_t *pData, uint16_t Size, uint32_t Timeout);
| ~~~~~~~~~^~~~~
../Core/Src/main.c: In function 'main':
../Core/Src/main.c:112:16: warning: passing argument 1 of 'send_to_uart' makes integer from pointer without a cast [-Wint-conversion]
112 | send_to_uart(greeting);
| ^~~~~~~~
| |
| uint8_t * {aka unsigned char *}
../Core/Src/main.c:65:28: note: expected 'uint8_t' {aka 'unsigned char'} but argument is of type 'uint8_t *' {aka 'unsigned char *'}
65 | void send_to_uart (uint8_t it_will_be_send)
| ~~~~~~~~^~~~~~~~~~~~~~~
../Core/Src/main.c:117:29: warning: pointer targets in passing argument 2 of 'HAL_UART_Transmit' differ in signedness [-Wpointer-sign]
117 | HAL_UART_Transmit(&huart2, "\nHAL some string to UART\n" , 25, 30);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
| |
| char *
In file included from ../Core/Inc/stm32f0xx_hal_conf.h:288,
from ../Drivers/STM32F0xx_HAL_Driver/Inc/stm32f0xx_hal.h:30,
from ../Core/Inc/main.h:31,
from ../Core/Src/main.c:21:
../Drivers/STM32F0xx_HAL_Driver/Inc/stm32f0xx_hal_uart.h:1491:73: note: expected 'uint8_t *' {aka 'unsigned char *'} but argument is of type 'char *'
1491 | HAL_StatusTypeDef HAL_UART_Transmit(UART_HandleTypeDef *huart, uint8_t *pData, uint16_t Size, uint32_t Timeout);
| ~~~~~~~~~^~~~~
../Core/Src/main.c:118:15: warning: passing argument 1 of 'send_to_uart' makes integer from pointer without a cast [-Wint-conversion]
118 | send_to_uart(some_string);
| ^~~~~~~~~~~
| |
| uint8_t * {aka unsigned char *}
../Core/Src/main.c:65:28: note: expected 'uint8_t' {aka 'unsigned char'} but argument is of type 'uint8_t *' {aka 'unsigned char *'}
65 | void send_to_uart (uint8_t it_will_be_send)
| ~~~~~~~~^~~~~~~~~~~~~~~
arm-none-eabi-gcc -o "max6675_2.0.elf" #"objects.list" -mcpu=cortex-m0 -T"C:\stm32\cubeMX_workspace\max6675_2.0\STM32F070RBTX_FLASH.ld" --specs=nosys.specs -Wl,-Map="max6675_2.0.map" -Wl,--gc-sections -static --specs=nano.specs -mfloat-abi=soft -mthumb -Wl,--start-group -lc -lm -Wl,--end-group
Finished building target: max6675_2.0.elf
arm-none-eabi-objdump -h -S max6675_2.0.elf > "max6675_2.0.list"
arm-none-eabi-objcopy -O binary max6675_2.0.elf "max6675_2.0.bin"
arm-none-eabi-size max6675_2.0.elf
text data bss dec hex filename
8228 20 1804 10052 2744 max6675_2.0.elf
Finished building: default.size.stdout
Finished building: max6675_2.0.bin
Finished building: max6675_2.0.list
13:39:29 Build Finished. 0 errors, 4 warnings. (took 1s.941ms)

Answer 1

Look at this:
void send_to_uart (uint8_t);
So send_to_uart expect an argument of type uint8_t - fine.
Now look at this:
uint8_t greeting[] = "Welcome to first circle of hell\n";
int main(void)
{
send_to_uart(greeting); <--- What is greeting?
So is greeting a uint8_t ?
No - it's not. It's an array so you can't pass it to a function that expects a uint8_t
Try like:
for (int i = 0; i < strlen(greeting); ++i) send_to_uart(greeting[i]);