gadget-tester/uart.c

/* 
 * (c) danielinux 2019
 *
 *      GPLv.2
 *
 * See LICENSE for details
 */
#include <stdint.h>
#include <stdio.h>
#include "uart.h"
#include "system.h"

#define UART2 (0x40004400)

#define UART2_SR       (*(volatile uint32_t *)(UART2))
#define UART2_DR       (*(volatile uint32_t *)(UART2 + 0x04))
#define UART2_BRR      (*(volatile uint32_t *)(UART2 + 0x08))
#define UART2_CR1      (*(volatile uint32_t *)(UART2 + 0x0c))
#define UART2_CR2      (*(volatile uint32_t *)(UART2 + 0x10))

#define UART_CR1_UART_ENABLE    (1 << 13)
#define UART_CR1_SYMBOL_LEN     (1 << 12)
#define UART_CR1_PARITY_ENABLED (1 << 10)
#define UART_CR1_PARITY_ODD     (1 << 9)
#define UART_CR1_TX_ENABLE      (1 << 3)
#define UART_CR1_RX_ENABLE      (1 << 2)
#define UART_CR2_STOPBITS       (3 << 12)
#define UART_SR_TX_EMPTY        (1 << 7)
#define UART_SR_RX_NOTEMPTY     (1 << 5)



#define APB1_CLOCK_ER           (*(volatile uint32_t *)(0x40023840))
#define UART2_APB1_CLOCK_ER_VAL 	(1 << 17)

#define AHB1_CLOCK_ER (*(volatile uint32_t *)(0x40023830))
#define GPIO_MODE_AF (2)
#define UART2_PIN_AF 7
#define UART2_RX_PIN 2
#define UART2_TX_PIN 3

static void uart2_pins_setup(void)
{
    uint32_t reg;
    AHB1_CLOCK_ER |= GPIOA_AHB1_CLOCK_ER;
    /* Set mode = AF */
    reg = GPIOA_MODE & ~ (0x03 << (UART2_RX_PIN * 2));
    GPIOA_MODE = reg | (2 << (UART2_RX_PIN * 2));
    reg = GPIOA_MODE & ~ (0x03 << (UART2_TX_PIN * 2));
    GPIOA_MODE = reg | (2 << (UART2_TX_PIN * 2));

    /* Alternate function: use low pins */
    reg = GPIOA_AFL & ~(0xf << ((UART2_TX_PIN) * 4));
    GPIOA_AFL = reg | (UART2_PIN_AF << ((UART2_TX_PIN) * 4));
    reg = GPIOA_AFL & ~(0xf << ((UART2_RX_PIN) * 4));
    GPIOA_AFL = reg | (UART2_PIN_AF << ((UART2_RX_PIN) * 4));
}

int uart2_setup(uint32_t bitrate, uint8_t data, char parity, uint8_t stop)
{
    uint32_t reg;
    int pin_rx, pin_tx, pin_af;
    /* Enable pins and configure for AF7 */
    uart2_pins_setup();
    /* Turn on the device */
    APB1_CLOCK_ER |= UART2_APB1_CLOCK_ER_VAL;

    /* Configure for TX */
    UART2_CR1 |= UART_CR1_TX_ENABLE;

    /* Configure clock */
    UART2_BRR =  cpu_freq / bitrate;

    /* Configure data bits */
    if (data == 8)
        UART2_CR1 &= ~UART_CR1_SYMBOL_LEN;
    else
        UART2_CR1 |= UART_CR1_SYMBOL_LEN;

    /* Configure parity */
    switch (parity) {
        case 'O':
            UART2_CR1 |= UART_CR1_PARITY_ODD;
            /* fall through to enable parity */
        case 'E':
            UART2_CR1 |= UART_CR1_PARITY_ENABLED;
            break;
        default:
            UART2_CR1 &= ~(UART_CR1_PARITY_ENABLED | UART_CR1_PARITY_ODD);
    }
    /* Set stop bits */
    reg = UART2_CR2 & ~UART_CR2_STOPBITS;
    if (stop > 1)
        UART2_CR2 = reg & (2 << 12);
    else
        UART2_CR2 = reg;

    /* Turn on uart */
    UART2_CR1 |= UART_CR1_UART_ENABLE;

    return 0;
}

int _write(void *r, uint8_t *text, int len)
{
    char *p = (char *)text;
    int i;
    volatile uint32_t reg;
    text[len - 1] = 0;
    while(*p) {
        do {
            reg = UART2_SR;
        } while ((reg & UART_SR_TX_EMPTY) == 0);
        UART2_DR = *p;
        p++;
    }
    return len;
}

/* commodity to print binary buffers */

void printbin(const uint8_t *buf, int len)
{
    int i;
    for (i = 0; i < len; i++) {
        if ((i % 16) == 0)
            printf("\r\n%08x: ", i);
        printf("%02x ", buf[i]);
    }
    printf("\r\n");
}