GPIO of Arm
We take the GPIO information from Broadcast Arm cpu booklet in gpio chapters
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#pragma once
#include "peripherals/gpio.h"
typedef enum _GpioFunc {
GFInput = 0,
GFOutput = 1,
GFAlt0 = 4,
GFAlt1 = 5,
GFAlt2 = 6,
GFAlt3 = 7,
GFAlt4 = 3,
GFAlt5 = 2
} GpioFunc;
void gpio_pin_set_func(u8 pinNumber, GpioFunc func);
void gpio_pin_enable(u8 pinNumber);
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Now we can write gpio.c file. we first locate bits with and gate then set them with or gate.
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#include "gpio.h"
#include "utils.h"
void gpio_pin_set_func(u8 pinNumber, GpioFunc func) {
u8 bitStart = (pinNumber * 3) % 30;
u8 reg = pinNumber / 10;
u32 selector = REGS_GPIO->func_select[reg];
selector &= ~(7 << bitStart);
selector |= (func << bitStart);
REGS_GPIO->func_select[reg] = selector;
}
void gpio_pin_enable(u8 pinNumber) {
REGS_GPIO->pupd_enable = 0;
delay(150);
REGS_GPIO->pupd_enable_clocks[pinNumber / 32] = 1 << (pinNumber % 32);
delay(150);
REGS_GPIO->pupd_enable = 0;
REGS_GPIO->pupd_enable_clocks[pinNumber / 32] = 0;
}
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Mini uart connection
First define all the function to send the data
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#pragma once
void uart_init();
char uart_recv();
void uart_send(char c);
void uart_send_string(char *str);
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Then the implementation of the functions in order to enable gpio pins and send string via uart
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#include "gpio.h"
#include "utils.h"
#include "peripherals/aux.h"
#include "mini_uart.h"
#define TXD 14
#define RXD 15
void uart_init() {
gpio_pin_set_func(TXD, GFAlt5);
gpio_pin_set_func(RXD, GFAlt5);
gpio_pin_enable(TXD);
gpio_pin_enable(RXD);
REGS_AUX->enables = 1;
REGS_AUX->mu_control = 0;
REGS_AUX->mu_ier = 0;
REGS_AUX->mu_lcr = 3;
REGS_AUX->mu_mcr = 0;
#if RPI_VERSION == 3
REGS_AUX->mu_baud_rate = 270; // = 115200 @ 250 Mhz
#endif
#if RPI_VERSION == 4
REGS_AUX->mu_baud_rate = 541; // = 115200 @ 500 Mhz
#endif
REGS_AUX->mu_control = 3;
uart_send('\r');
uart_send('\n');
uart_send('\n');
}
void uart_send(char c) {
while(!(REGS_AUX->mu_lsr & 0x20));
REGS_AUX->mu_io = c;
}
char uart_recv() {
while(!(REGS_AUX->mu_lsr & 1));
return REGS_AUX->mu_io & 0xFF;
}
void uart_send_string(char *str) {
while(*str) {
if (*str == '\n') {
uart_send('\r');
}
uart_send(*str);
str++;
}
}
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