LED Control

The tutorial demonstrates controlling the LED on and off.

The tutorial only introduces the standard library project code

Hardware connection

Control principle

By controlling the PB3 pin to output high and low levels, the LED can be turned on and off.

Bit-band operation

xxxxxxxxxx
For specific implementation ideas, refer to Chapter 5 (pages 87 to 92) of <<CM3 Authoritative Guide>>

Using bit-band operation, you can read and write a single bit of the memory.

• Bit-band area: address area supporting bit-band operation

• Bit-band alias: access to alias address ultimately affects access to bit-band area

Range of two memory areas supporting bit-band operation

• SRAM bit-band area address: 0x2000 0000 - 0x200F FFFF

• Peripheral bit-band area address: 0x4000 0000 - 0x400F FFFF

Bit-band alias area

A: byte address

n: bit number (0≤n≤7)

• SRAM bit-band alias area address: 0x2200 0000 - 0x23FF FFFC

xxxxxxxxxx
AliasAddr= =0x22000000+ ((A-0x20000000)*8 +n)*4

• Peripheral bit-band alias area address: 0x4200 0000 - 0x43FF FFFC

xxxxxxxxxx
AliasAddr= =0x42000000+ ((A-0x40000000)*8 +n)*4

Advantages

You can directly control the bits of the hardware register to improve program execution efficiency!

Code

​x
// A macro that converts "bit with address + bit serial number" to an alias address
#define BITBAND(addr, bitnum) ((addr & 0xF0000000)+0x2000000+((addr &0xFFFFF)<<5)+(bitnum<<2))
// Converts an address to a pointer
#define MEM_ADDR(addr)  *((volatile unsigned long  *)(addr))
// Converts the bit-tape alias area address to a pointer
#define BIT_ADDR(addr, bitnum)   MEM_ADDR(BITBAND(addr, bitnum))

// GPIO ODR and IDR register address mapping
#define GPIOA_ODR_Addr    (GPIOA_BASE+12) //0x4001080C
#define GPIOB_ODR_Addr    (GPIOB_BASE+12) //0x40010C0C
#define GPIOC_ODR_Addr    (GPIOC_BASE+12) //0x4001100C
#define GPIOD_ODR_Addr    (GPIOD_BASE+12) //0x4001140C
#define GPIOE_ODR_Addr    (GPIOE_BASE+12) //0x4001180C
#define GPIOF_ODR_Addr    (GPIOF_BASE+12) //0x40011A0C
#define GPIOG_ODR_Addr    (GPIOG_BASE+12) //0x40011E0C

#define GPIOA_IDR_Addr    (GPIOA_BASE+8)  //0x40010808
#define GPIOB_IDR_Addr    (GPIOB_BASE+8)  //0x40010C08
#define GPIOC_IDR_Addr    (GPIOC_BASE+8)  //0x40011008
#define GPIOD_IDR_Addr    (GPIOD_BASE+8)  //0x40011408
#define GPIOE_IDR_Addr    (GPIOE_BASE+8)  //0x40011808
#define GPIOF_IDR_Addr    (GPIOF_BASE+8)  //0x40011A08
#define GPIOG_IDR_Addr    (GPIOG_BASE+8)  //0x40011E08

// Operate an I/O port of GPIO alone, n(0,1,2...) 15),n indicates the specific I/O port
#define PAout(n) BIT_ADDR(GPIOA_ODR_Addr,n) // Output
#define PAin(n) BIT_ADDR(GPIOA_IDR_Addr,n) // Enter

#define PBout(n) BIT_ADDR(GPIOB_ODR_Addr,n) // Output
#define PBin(n) BIT_ADDR(GPIOB_IDR_Addr,n) // Input

#define PCout(n) BIT_ADDR(GPIOC_ODR_Addr,n) // Output
define PCin(n) BIT_ADDR(GPIOC_IDR_Addr,n) // Enter

#define PDout(n) BIT_ADDR(GPIOD_ODR_Addr,n) // Output
#define PDin(n) BIT_ADDR(GPIOD_IDR_Addr,n) // Enter this parameter

#define PEout(n) BIT_ADDR(GPIOE_ODR_Addr,n) // Output
#define PEin(n) BIT_ADDR(GPIOE_IDR_Addr,n) // Enter a value

#define PFout(n) BIT_ADDR(GPIOF_ODR_Addr,n) // Output
#define PFin(n) BIT_ADDR(GPIOF_IDR_Addr,n) // Enter

#define PGout(n) BIT_ADDR(GPIOG_ODR_Addr,n) // Output
#define PGin(n) BIT_ADDR(GPIOG_IDR_Addr,n) // Input

Example

PB3 output low

The following code actually works the same, the bitband operation is relatively simpler and faster!

• Standard Library

xxxxxxxxxx
GPIO_ResetBits(GPIOB,GPIO_Pin_3)
GPIO_WriteBit(GPIOB, GPIO_Pin_3, Bit_RESET)

• Bit band operation

xxxxxxxxxx
PBout(3)  = 0;

Software configuration

Pin definition

Software code

Since the default function of the PB3 pin is the JTDO function, we need to disable its function and configure the PB3 as a normal IO pin function.

xxxxxxxxxx
Product supporting information source path: attachment → source summary → 1.Base_Course → 2.LED

control function

The tutorial only briefly introduces the code, the specific can open the project source code to read.

Init_Led_GPIO

xxxxxxxxxx
void Init_Led_GPIO(void)
{
    GPIO_InitTypeDef GPIO_InitStructure;
    RCC_APB2PeriphClockCmd(LED_RCC, ENABLE);
    GPIO_InitStructure.GPIO_Pin = LED_PIN;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_2MHz;
    GPIO_Init(LED_PORT, &GPIO_InitStructure);
    LED = 0;
}

Experimental phenomenon

The LEd.hex file generated by the project compilation is located in the OBJ folder of the LED project, find the corresponding LEd.hex file of the project and use FlyMcu software to download the program into the development board.

After the program is successfully downloaded, the LED switches on and off every 500ms.