{"id":14071,"date":"2023-02-25T10:30:19","date_gmt":"2023-02-25T05:00:19","guid":{"rendered":"https:\/\/fastbitlab.com\/?p=14071"},"modified":"2023-09-16T12:25:27","modified_gmt":"2023-09-16T06:55:27","slug":"microcontroller-embedded-c-programming-lecture-184-modifying-led-toggle-exercise-with-macros","status":"publish","type":"post","link":"https:\/\/fastbitlab.com\/blog\/microcontroller-embedded-c-programming-lecture-184-modifying-led-toggle-exercise-with-macros\/","title":{"rendered":"Microcontroller Embedded C Programming Lecture 184| Modifying led toggle exercise with macros"},"content":{"rendered":"
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Modifying led toggle exercise with macros<\/span><\/strong><\/h1>\n
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In C, macros are used to define reusable pieces of code or constants that are substituted directly into the code during preprocessing. Macros are preprocessor directives and are typically defined using the #define<\/strong><\/span> directive. <\/span><\/p>\n

In this article, we will enhance our previous program, led_toggle_bitfields, by incorporating macros to make the code more organized and readable.  Macros are a powerful tool for simplifying code and abstracting away complex values or addresses.<\/span><\/p>\n

Let\u2019s modify the below code and let’s see where and all we can make use of macros here. <\/span><\/p>\n

#include<\/span> \"main.h\"\r\n\r\nint<\/span> main(void<\/span>)\r\n{\r\n   RCC_AHB1ENR_t<\/span> volatile<\/span> *const<\/span> pClkCtrlReg = (RCC_AHB1ENR_t<\/span>*) 0x40023830;\r\n   GPIOx_MODE_t<\/span> volatile<\/span> *const<\/span> pPortDModeReg = (GPIOx_MODE_t<\/span>*) 0x40020C00;\r\n   GPIOx_ODR_t<\/span> volatile<\/span> *const<\/span> pPortDOutReg = (GPIOx_ODR_t<\/span>*) 0x40020C14;\r\n\r\n   \/\/1. enable the clock for GPOID peripheral in the AHB1ENR (SET the 3rd bit position)<\/span>\r\n   pClkCtrlReg->gpiod_en = 1;\r\n\r\n   \/\/2. configure the mode of the IO pin as output<\/span>\r\n   pPortDModeReg->pin_12 = 1;\r\n\r\n   while<\/span>(1)\r\n   {\r\n      \/\/Set 12th bit of the output data register to make I\/O pin-12 as HIGH<\/span>\r\n      pPortDOutReg->pin_12 = 1;\r\n\r\n      \/\/introduce small human observable delay<\/span>\r\n     \/\/This loop executes for 300K times<\/span>\r\n     for<\/span>(uint32<\/span>_t i=0 ; i < 300000 ; i++ );\r\n\r\n     \/\/Reset 12th bit of the output data register to make I\/O pin-12 as LOW<\/span>\r\n     pPortDOutReg->pin_12 = 0;\r\n\r\n    for<\/span>(uint32_t<\/span> i=0 ; i < 300000 ; i++ );\r\n   }\r\n\r\n   for<\/span>(;;);\r\n}<\/pre>\n
led_toggle_bitfields program code<\/span><\/p>\n
Define a Macro:<\/strong><\/span><\/p>\n
To define a macro, use the #define<\/code> directive followed by the macro name and its replacement value.<\/span><\/p>\n
The defined macros are shown in Figure 1 and the Modified code is below code snippet. <\/span><\/p>\n
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Here, there is an address represented as (RCC_AHB1ENR_t*) 0x40023830. To hide this number, a macro can be used. This can be achieved by creating macros in main.h.<\/span><\/p>\n
The number 0x40023830 is the register address of the AHB1_ENR register. A macro named ADDR_REG_AHB1ENR can be created with the value ((RCC_AHB1ENR_t*) 0x40023830) to represent this address. <\/span><\/p>\n
#define ADDR_REG_AHB1ENR    (   (RCC_AHB1ENR_t*)    0x40023830)<\/b><\/span><\/p>\n
Similar to ADDR_REG_AHB1ENR, two more macros can be created for GPIOD_MODE and GPIOD_OD, named ADDR_REG_GPIOD_MODE and ADDR_REG_GPIOD_OD respectively with their corresponding values.<\/span><\/p>\n
#define ADDR_REG_GPIOD_MODE   (  (GPIOx_MODE_t*)   0x40020C00)<\/b><\/span><\/p>\n
#define ADDR_REG_GPIOD_OD          (  (GPIOx_ODR_t*)      0x40020C14) <\/b><\/span><\/p>\n
According to our guideline for writing macros, a macro value must be inside parentheses. That’s why let’s use the parentheses here. <\/span><\/p>\n
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Figure 1. Some macros in main.h<\/span><\/figcaption><\/figure>\n
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#include<\/span> \"main.h\"\r\n\r\nint<\/span> main(void<\/span>)\r\n{\r\n   RCC_AHB1ENR_t<\/span> volatile<\/span> *const<\/span> pClkCtrlReg   = ADDR_REG_AHB1ENR;;\r\n   GPIOx_MODE_t<\/span>  volatile<\/span> *const<\/span> pPortDModeReg = ADDR_REG_GPIOD_MODE; \r\n   GPIOx_ODR_t<\/span>   volatile<\/span> *const<\/span> pPortDOutReg  = ADDR_REG_GPIOD_OD;\r\n\r\n   \/\/1. enable the clock for GPOID peripheral in the AHB1ENR (SET the 3rd bit position)<\/span>\r\n   pClkCtrlReg->gpiod_en = CLOCK_ENABLE;\r\n\r\n   \/\/2. configure the mode of the IO pin as output<\/span>\r\n   pPortDModeReg->pin_12 = MODE_CONF_OUTPUT; \r\n\r\n  while<\/span>(1)\r\n  {\r\n  \/\/Set 12th bit of the output data register to make I\/O pin-12 as HIGH<\/span>\r\n  pPortDOutReg->pin_12 = PIN_STATE_HIGH;\r\n\r\n  \/\/introduce small human observable delay<\/span>\r\n  \/\/This loop executes for 300K times<\/span>\r\n  for<\/span>(uint32<\/span>_t i=0 ; i < DELAY_COUNT ; i++ );\r\n\r\n  \/\/Reset 12th bit of the output data register to make I\/O pin-12 as LOW<\/span>\r\n  pPortDOutReg->pin_12 = PIN_STATE_LOW;\r\n\r\n  for<\/span>(uint32_t<\/span> i=0 ; i < DELAY_COUNT ; i++ );\r\n  }\r\n\r\n for<\/span>(;;);\r\n}<\/pre>\n
Modified code in main.c<\/span><\/p>\n
1. Enable the clock for the GPIOD peripheral in the AHB1ENR(SET the 3rd-bit position)<\/span><\/p>\n
pClkCtrlReg-> gpiod_en = 1;<\/b><\/span><\/p>\n
Here, 1 means enable. We can create a meaningful macro named CLOCK_ENABLE for 1. <\/span><\/p>\n
pClkCtrlReg -> gpiod_en = CLOCK_ENABLE; <\/b><\/span><\/span><\/p>\n
And define it as <\/span>#define CLOCK_ENABLE (1)<\/b><\/span>;<\/span> <\/span><\/span><\/p>\n
When someone sees this code, then it is very clear to them that you are doing some ClOCK_ENABLE thing here.<\/span><\/p>\n
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2. Configure the mode of the IO pin as output<\/span><\/p>\n
Similarly, we can create a macro named MODE_CONF_OUTPUT for configuring the mode of the IO pin as output <\/span><\/p>\n
pPortDMODEReg -> pin_12 = MODE_CONF_OUTPUT;<\/span><\/b><\/span><\/p>\n
And define it as <\/span>#define MODE_CONF_OUTPUT (1)<\/b><\/span>  <\/span><\/span><\/p>\n
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