#include <stdio.h>

Remember to include a terminating “\n” in your printf – stdout doesn’t flush until it encounters one by default!!!!

If printf still doesn’t occur you may need fflush(stdout); or consider using std::cout instead

	printf("Hello world!\n");

	printf("%i bytes read : %s\n", rx_length, rx_buffer);

	printf("data_h: %02X\n", sensor_data_h);

printf format codes

bool %d
int %d
int %i
int8_t %hhd
uint8_t %hhu
int16_t %hd
uint16_t %hu
int32_t %ld
uint32_t %lu
int64_t %lld
uint64_t %llu
char[] %s
float %e (up to 6 digits of precision)
float %g (up to 6 digits of precision)
double %lf (up to 6 digits of precision using standard decimal notation, without any trailing zeros)
double %lg (up to 6 digits of precision which can use scientific notation if its shorter)

//Displaying hex:
uin16_t 0x%04X (display 4 characters of hex)

//Alternative bool
printf("%s", x ? "true" : "false");

d or i – int, decimal (base ten) number

x or X – int, hexadecimal number.  Also “%02x” to specify length of digits

ld – long, decimal number (‘l’ can also be applied to any of the above to change the type from ‘int’ to ‘long’)

u – unsigned, decimal number

lu – unsigned long, decimal number

llu – unsigned long long, decimal number (uint64_t)

c – char, single character

s – char pointer, string

f – float, number with six digits of precision
g – float, number with up to six digits of precision
e – float, number with up to six digits of precision, scientific notation
lf – double, number with six digits of precision
lg – double, number with up to six digits of precision
le – double, number with up to six digits of precision, scientific notation

Including values examples

Hex values

	//Include a 2 digit HEX value "%02"
	printf("MyValue: 0x%02X\n", (uint16_t)SwitchInputs);

	//Include a 4 digit HEX value "%04"
	printf("MyValue: 0x%04X\n", (uint16_t)SwitchInputs);

Int values

	//Force to 2 digits
	printf("MyValue: %02i\n", (uint16_t)TimeHours);

Result of an operation

	printf((err != ESP_OK) ? "Failed!\n" : "Done\n");

printf in a multi-thread environment

Watch out for clashes causing bugs!  This can happen with irq’s using printf, different threads using it, etc.

Using a semaphore to protect

This is one option to stop clahses, e.g.

#include "semphr.h"

//Create semphore
SemaphoreHandle_t print_semaphore = NULL;

	print_semaphore = xSemaphoreCreateMutex();
    
    
//Use sempahore
	xSemaphoreTake(print_semaphore, portMAX_DELAY);
	printf("Something");
	printf("Something");
	xSemaphoreGive(print_semaphore);