![\"\"](\"https:\/\/blog.embeddedexpert.io\/wp-content\/uploads\/2023\/07\/AdobeStock_128586024-2-1024x683.jpeg\")
<\/figure>\n\n\n\n<\/p>\n\n\n\n
In the previous part of this guide (here<\/a>), we took a look at how to configure the SysTick to generate ticks for the system for timing, delay etc. Also, in part 1 (here<\/a>), we saw how to configure the GPIO in analog mode, input and output. In this guide, we shall see how to configure the pin in alternate functuon.<\/p>\n\n\n\n <\/p>\n\n\n\n In this guide, we shall cover the following:<\/p>\n\n\n\n <\/p>\n\n\n\n <\/p>\n\n\n\n Within the following function , bsp.c source code:<\/p>\n\n\n\n We shall check if the pin mode is alternate function as following:<\/p>\n\n\n\n If it is, set the required pin mode to 00 (general purpose input) as following:<\/p>\n\n\n\n Set the mode:<\/p>\n\n\n\n Set the following:<\/p>\n\n\n\n Now, we shall set the type of the alternate function.<\/p>\n\n\n\n First check if the pin between 0 and 7 or between 8 and 15.<\/p>\n\n\n\n <\/p>\n\n\n\n The reason behind this checking since the AFR register is divided in low and high part as following:<\/p>\n\n\n\n <\/p>\n\n\n\n <\/p>\n\n\n\n <\/p>\n\n\n\n <\/p>\n\n\n\n The low will handle the pins from 0 to 7 while high part will handle pins from 8 to 15.<\/p>\n\n\n\n <\/p>\n\n\n\n First if the pin between pin 0 and pin 7:<\/p>\n\n\n\n <\/p>\n\n\n\n Since the settings is 4-bit wide, we shall multiply the pin number by 4 which will set the required pin to alternate number function.<\/p>\n\n\n\n If the pin between 8 and 15:<\/p>\n\n\n\n <\/p>\n\n\n\n Hence, the part of alternate function as following:<\/p>\n\n\n\n <\/p>\n\n\n\n <\/p>\n\n\n\n You may get the code from this github repository:<\/p>\n\n\n\n1. GPIO Configuration in alternate function:<\/h2>\n\n\n\n
void GPIO_Initialization(GPIO_TypeDef *GPIO,GPIO_Configure_Typedef * GPIO_Config)<\/pre><\/div>\n\n\n\n
if (GPIO_Config->Mode == Alternate_function)<\/pre><\/div>\n\n\n\n
GPIO->MODER &=~((0x03<<(GPIO_Config->PinNumber*2)));<\/pre><\/div>\n\n\n\n
GPIO->MODER|= (GPIO_Config->Mode<< GPIO_Config->PinNumber*2);<\/pre><\/div>\n\n\n\n
\t\tGPIO->OTYPER|= (GPIO_Config->OutputType<<GPIO_Config->PinNumber);\n\n\t\tGPIO->OSPEEDR|= (GPIO_Config->OutPutspeed<< GPIO_Config->PinNumber*2);\n\n\t\tGPIO->PUPDR|= (GPIO_Config->PullUp_PullDown<< GPIO_Config->PinNumber*2);<\/pre><\/div>\n\n\n\n
![\"\"](\"https:\/\/blog.embeddedexpert.io\/wp-content\/uploads\/2023\/07\/Screenshot-2023-07-09-at-8.17.07-AM-1024x341.png\")
<\/figure>\n\n\n\n![\"\"](\"https:\/\/blog.embeddedexpert.io\/wp-content\/uploads\/2023\/07\/Screenshot-2023-07-09-at-8.17.15-AM-1024x341.png\")
<\/figure>\n\n\n\n\t\tif (GPIO_Config->PinNumber <=pin7)\n\t\t{\n\t\t\tGPIO->AFR[0]= (GPIO_Config->AlternateType << GPIO_Config->PinNumber *4);\n\t\t}<\/pre><\/div>\n\n\n\n\t\tif (GPIO_Config->PinNumber>pin7 && GPIO_Config->PinNumber<=pin15)\n\t\t{\n\t\t\tGPIO->AFR[1]= (GPIO_Config->AlternateType << (GPIO_Config->PinNumber-8) *4);\n\t\t}<\/pre><\/div>\n\n\n\n\tif (GPIO_Config->Mode == Alternate_function)\n\t{\n\t\tGPIO->MODER &=~((0x03<<(GPIO_Config->PinNumber*2)));\n\t\tGPIO->MODER|= (GPIO_Config->Mode<< GPIO_Config->PinNumber*2);\n\n\t\tGPIO->OTYPER|= (GPIO_Config->OutputType<<GPIO_Config->PinNumber);\n\n\t\tGPIO->OSPEEDR|= (GPIO_Config->OutPutspeed<< GPIO_Config->PinNumber*2);\n\n\t\tGPIO->PUPDR|= (GPIO_Config->PullUp_PullDown<< GPIO_Config->PinNumber*2);\n\n\t\tif (GPIO_Config->PinNumber <=pin7)\n\t\t{\n\t\t\tGPIO->AFR[0]= (GPIO_Config->AlternateType << GPIO_Config->PinNumber *4);\n\t\t}\n\n\t\tif (GPIO_Config->PinNumber>pin7 && GPIO_Config->PinNumber<=pin15)\n\t\t{\n\t\t\tGPIO->AFR[1]= (GPIO_Config->AlternateType << (GPIO_Config->PinNumber-8) *4);\n\t\t}\n\n\t}<\/pre><\/div>\n\n\n\n2. Code:<\/h2>\n\n\n\n
![\"\"](\"https:\/\/blog.embeddedexpert.io\/wp-content\/uploads\/2023\/07\/Screenshot-2023-07-09-at-8.31.04-AM-923x1024.png\")
<\/figure>\n\n\n\n