[英]Neat/compact C code for working with multiple GPIO ports on a microcontroller
I'm writing a program where I need to control many output pins on my Atmega4809.我正在编写一个程序,我需要在我的 Atmega4809 上控制许多 output 引脚。 How can I work with these without having to write duplicate code (using loops and arrays for example)?我如何在不必编写重复代码的情况下使用这些代码(例如使用循环和 arrays)?
Instead of doing this...而不是这样做......
PORTA.OUT |= (1 << PIN2);
PORTB.OUT |= (1 << PIN4);
PORTC.OUT |= (1 << PIN1);
PORTD.OUT |= (1 << PIN3);
.. I want to do something like this ..我想做这样的事情
for (int i = 0; i < 4; i++) {
myPorts[i].OUT |= (1 << myPins[i];
}
I tried to #define
all the ports and pins, and putting them in arrays like this: (for context the output pins are connected to rows and columns of an LED_matrix)我试图#define
所有端口和引脚,并将它们放在 arrays 中,如下所示:(对于上下文,output 引脚连接到 LED_matrix 的行和列)
#define COL0_PORT PORTF
#define COL1_PORT PORTD
#define COL2_PORT PORTA
#define COL3_PORT PORTB
PORT_t col_ports[] = {COL0_PORT, COL1_PORT, COL2_PORT, COL3_PORT};
When building, I get "initializer element is not constant".构建时,我得到“初始化器元素不是常量”。
Assuming that variables like PORTA
have type PORT_t
, then you can store pointers to them in an array using this syntax:假设PORTA
等变量的类型为PORT_t
,那么您可以使用以下语法将指向它们的指针存储在数组中:
PORT_t * col_ports[] = { &PORTA, &PORTA, &PORTF, &PORTB };
You might try putting the const
keyword right before col_ports
as well;您也可以尝试将const
关键字放在col_ports
之前; that might move the array to flash, thus saving you some RAM space.这可能会将数组移动到 flash,从而为您节省一些 RAM 空间。
Assuming 8 bit MCU with 16 bit register map, then your ports will be defined in a register map along the lines of this:假设 8 位 MCU 具有 16 位寄存器 map,那么您的端口将在寄存器 map 中定义,如下所示:
#define PORTA (*(volatile uint8_t*)0x1234u)
Why is explained here: How to access a hardware register from firmware?为什么在这里解释: How to access a hardware register from firmware?
You will want an array of volatile uint8_t*
pointers: volatile uint8_t* col_ports[]
.您将需要一个volatile uint8_t*
指针数组: volatile uint8_t* col_ports[]
。 However, you most likely also want this array to be allocated in flash not RAM, therefore add const
after the *
, to make the array itself read-only:但是,您很可能还希望将此数组分配到 flash 而不是 RAM,因此在*
之后添加const
以使数组本身成为只读的:
volatile uint8_t* const col_ports[] =
{
&PORTA,
&PORTB,
&PORTC
};
There might also be various memory mapping hiccups related to the old AVR Harvard architecture, so you might have to add PROGMEM
after the const
, or similar compiler-specific non-standard keywords.可能还存在与旧 AVR Harvard 架构相关的各种 memory 映射问题,因此您可能必须在const
或类似的特定于编译器的非标准关键字之后添加PROGMEM
。
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