Spyros Papanastasiou / Mbed 2 deprecated Write_to_port_directly__LED

Example program for Port access. Blink the LED using the registers.

Dependencies:   mbed

main.cpp@1:65c259961c26, 2019-07-22 (annotated)

Committer:
Ladon
Date:
Mon Jul 22 12:32:29 2019 +0000
Revision:
1:65c259961c26
Parent:
0:e637d54ba0a3
Child:
2:f72c56822d58
Added a book reference.

Who changed what in which revision?

UserRevisionLine numberNew contents of line
Ladon 0:e637d54ba0a3 1 #include <mbed.h>
Ladon 0:e637d54ba0a3 2
Ladon 1:65c259961c26 3 // Board: NUCLEO-F303RE (STM32F303RE).
Ladon 0:e637d54ba0a3 4 // -
Ladon 0:e637d54ba0a3 5
Ladon 0:e637d54ba0a3 6 // We shall write to PA5 where the LED is..
Ladon 0:e637d54ba0a3 7 // Info: LEDs:
Ladon 0:e637d54ba0a3 8 // https://www.st.com/resource/en/user_manual/dm00105823.pdf (UM1724: STM32 Nucleo-64 boards (MB1136))
Ladon 1:65c259961c26 9 //
Ladon 0:e637d54ba0a3 10 // Info: Talking to ports:
Ladon 0:e637d54ba0a3 11 // https://developer.arm.com/tools-and-software/embedded/legacy-tools/ds-5-development-studio/resources/tutorials/accessing-memory-mapped-peripherals
Ladon 1:65c259961c26 12 // More info: Chapter 25.4.1 from "2014 Programming Principles and Practice Using C++"
Ladon 1:65c259961c26 13 /// (https://archive.org/details/2014ProgrammingPrinciplesAndPracticeUsingCPlusPlus/page/n636)
Ladon 1:65c259961c26 14 //
Ladon 0:e637d54ba0a3 15 // Info: #defines :
Ladon 0:e637d54ba0a3 16 // https://raw.githubusercontent.com/ARMmbed/mbed-os/master/targets/TARGET_STM/TARGET_STM32F3/TARGET_STM32F303xE/device/stm32f303xe.h
Ladon 1:65c259961c26 17 //
Ladon 0:e637d54ba0a3 18 // Reference manual:
Ladon 0:e637d54ba0a3 19 // https://www.st.com/resource/en/reference_manual/dm00043574.pdf
Ladon 0:e637d54ba0a3 20 // -
Ladon 0:e637d54ba0a3 21 // We 'll need the MODER (port mode) register (see ^reference manual) and the ODR (output data register).
Ladon 0:e637d54ba0a3 22 // Register addresses are calculated taking the GPIOA base address (found in the reference manual) and adding the appropriate register's offset to it.
Ladon 0:e637d54ba0a3 23 // -
Ladon 0:e637d54ba0a3 24 // Note:
Ladon 0:e637d54ba0a3 25 // I was unsuccessfull in the following:
Ladon 0:e637d54ba0a3 26 //
Ladon 0:e637d54ba0a3 27 // #define ODR ((volatile unsigned short*) (GPIOA + 0x14)
Ladon 0:e637d54ba0a3 28 // -
Ladon 0:e637d54ba0a3 29
Ladon 0:e637d54ba0a3 30 #define MODER ((volatile unsigned int*) 0x48000000)
Ladon 0:e637d54ba0a3 31 // 32 bits.
Ladon 0:e637d54ba0a3 32 // We 'll set pins 11,10 set to 0,1.
Ladon 0:e637d54ba0a3 33 // -
Ladon 0:e637d54ba0a3 34
Ladon 0:e637d54ba0a3 35 #define ODR ((volatile unsigned short*) 0x48000014)
Ladon 0:e637d54ba0a3 36 // 16 bits.
Ladon 0:e637d54ba0a3 37 // We 'll write at pin 5.
Ladon 0:e637d54ba0a3 38 // -
Ladon 0:e637d54ba0a3 39
Ladon 0:e637d54ba0a3 40 // More FUN (dwarf fortress reference).
Ladon 0:e637d54ba0a3 41 // -
Ladon 0:e637d54ba0a3 42 #define OTYPER ((volatile unsigned short*) (0x48000004))
Ladon 0:e637d54ba0a3 43 #define PUPDR ((volatile unsigned int*) (0x4800000C))
Ladon 0:e637d54ba0a3 44 #define BSRR ((volatile unsigned int*) (0x48000018))
Ladon 0:e637d54ba0a3 45 #define LCKR ((volatile unsigned int*) (0x4800001C))
Ladon 0:e637d54ba0a3 46 #define AFRL ((volatile unsigned int*) (0x48000020))
Ladon 0:e637d54ba0a3 47
Ladon 0:e637d54ba0a3 48 void set_bit_as_output ()
Ladon 0:e637d54ba0a3 49 {
Ladon 0:e637d54ba0a3 50 // Set to output.
Ladon 0:e637d54ba0a3 51 // -
Ladon 0:e637d54ba0a3 52 unsigned int moder = *MODER;
Ladon 0:e637d54ba0a3 53 moder |= 0x00000400U;
Ladon 0:e637d54ba0a3 54 moder &= 0xFFFFF7FFU;
Ladon 0:e637d54ba0a3 55 // ^ Write 0,1 to bits 11,10.
Ladon 0:e637d54ba0a3 56 // -
Ladon 0:e637d54ba0a3 57 *MODER = moder;
Ladon 0:e637d54ba0a3 58 }
Ladon 0:e637d54ba0a3 59
Ladon 0:e637d54ba0a3 60 void toggle_bit ()
Ladon 0:e637d54ba0a3 61 {
Ladon 0:e637d54ba0a3 62 ///*
Ladon 0:e637d54ba0a3 63 static unsigned short state = 0;
Ladon 0:e637d54ba0a3 64 state ^= 0x20;
Ladon 0:e637d54ba0a3 65 *ODR = state;
Ladon 0:e637d54ba0a3 66 //*/
Ladon 0:e637d54ba0a3 67 /*
Ladon 0:e637d54ba0a3 68 static bool state = false;
Ladon 0:e637d54ba0a3 69 if (state)
Ladon 0:e637d54ba0a3 70 {
Ladon 0:e637d54ba0a3 71 *BSRR = 0x00200000U;
Ladon 0:e637d54ba0a3 72 }
Ladon 0:e637d54ba0a3 73 else
Ladon 0:e637d54ba0a3 74 {
Ladon 0:e637d54ba0a3 75 *BSRR = 0x00000020U;
Ladon 0:e637d54ba0a3 76 }
Ladon 0:e637d54ba0a3 77 state = !state;
Ladon 0:e637d54ba0a3 78 */
Ladon 0:e637d54ba0a3 79 }
Ladon 0:e637d54ba0a3 80
Ladon 0:e637d54ba0a3 81 int main ()
Ladon 0:e637d54ba0a3 82 {
Ladon 0:e637d54ba0a3 83 set_bit_as_output();
Ladon 0:e637d54ba0a3 84 while (true)
Ladon 0:e637d54ba0a3 85 {
Ladon 0:e637d54ba0a3 86 toggle_bit();
Ladon 0:e637d54ba0a3 87 /*
Ladon 0:e637d54ba0a3 88 printf("MODER = 0x%X\n", *MODER);
Ladon 0:e637d54ba0a3 89 printf("OTYPER = 0x%X\n", *OTYPER);
Ladon 0:e637d54ba0a3 90 printf("PUPDR = 0x%X\n", *PUPDR);
Ladon 0:e637d54ba0a3 91 printf("ODR = 0x%hX\n", *ODR);
Ladon 0:e637d54ba0a3 92 printf("LCKR = 0x%X\n", *LCKR);
Ladon 0:e637d54ba0a3 93 printf("AFRL = 0x%X\n", *AFRL);
Ladon 0:e637d54ba0a3 94 printf("\n");
Ladon 0:e637d54ba0a3 95 */
Ladon 0:e637d54ba0a3 96 wait(0.65);
Ladon 0:e637d54ba0a3 97 // ^ : https://os.mbed.com/docs/mbed-os/v5.13/apis/wait.html
Ladon 0:e637d54ba0a3 98 // -
Ladon 0:e637d54ba0a3 99 }
Ladon 0:e637d54ba0a3 100 }