Graphics, sound and multimedia • Re: Midi, I2C, Pi 5 RP1 chip, which gpio lib???

Code:

#include <stdio.h>#include <stdarg.h>#include <string.h>#include <errno.h>#include <fcntl.h>#include <asm/termios.h>#include <unistd.h>typedef unsigned char u8;// Global variable for holding file descriptor to talk to UART0 for MIDI communications:int uart0_fd = -1;// Default UART0 device name on Raspberry Pi Model B:const char *midi_fname = "/dev/ttyAMA0";// Open UART0 device for MIDI communications and set baud rate to 31250 per MIDI standard:int midi_init(void) {    struct termios2 tio;    uart0_fd = open(midi_fname, O_RDWR | O_NOCTTY | O_NONBLOCK);    if (uart0_fd == -1) {        char err[100];        sprintf(err, "open('%s')", midi_fname);        perror(err);        return -1;    }    // Requirements:    //   * UART0 is enabled    //   * UART0 is unused by the system for any ttys (remove mention of ttyAMA0 from `/etc/inittab`)    //   * UART0 clock rate is set to default of 3MHz in /boot/config.txt    //     * `init_uart_clock=3000000`    //   * UART0 clock rate for Linux is set to default of 3MHz in /boot/cmdline.txt    //     * `bcm2708.uart_clock=3000000`    //    // NOTE: Any hacks to change the default UART clock speed of the RPi B to adjust the    // standard baud rates of 38400 to actually be ~31250 DO NOT WORK on latest Raspbian    // kernels. I'm using `Linux 4.1.18 armv6l` as of 2017-02-20.    //    // The only thing that DOES work on latest Raspbian kernels is the code below which uses    // termios2 to set a custom baud rate of 31250 which is the MIDI standard.        // Set baud rate to 31250 for MIDI:    ioctl(uart0_fd, TCGETS2, &tio);    tio.c_cflag &= ~CBAUD;    tio.c_cflag |= BOTHER;    tio.c_ispeed = 31250;    tio.c_ospeed = 31250;    ioctl(uart0_fd, TCSETS2, &tio);    return uart0_fd;}void midi_send_cmd1_impl(u8 cmd_byte, u8 data1) {    int count;    u8 buf[2];    buf[0] = cmd_byte;    buf[1] = data1;    count = write(uart0_fd, buf, 2);    if (count != 2) {        perror("Error sending MIDI bytes");        return;    }    printf("MIDI: %02X %02X\n", cmd_byte, data1);}void midi_send_cmd2_impl(u8 cmd_byte, u8 data1, u8 data2) {    int count;    u8 buf[3];    buf[0] = cmd_byte;    buf[1] = data1;    buf[2] = data2;    count = write(uart0_fd, buf, 3);    if (count != 3) {        perror("Error sending MIDI bytes");        return;    }    printf("MIDI: %02X %02X %02X\n", cmd_byte, data1, data2);}// 256 byte buffer for batching up SysEx data to send in one write() call:u8 sysex[256];size_t sysex_p = 0;// Buffer up SysEx data until terminating F7 byte is encountered:void midi_send_sysex(u8 byte) {    //printf("MIDI: %02X\n", byte);    if (sysex_p >= 256) {        fprintf(stderr, "MIDI SysEx data too large (>= 256 bytes)\n");        return;    }    // Buffer data:    sysex[sysex_p++] = byte;    if (byte == 0xF7) {        size_t i;        size_t write_count = sysex_p;        sysex_p = 0;        printf("MIDI SysEx:");        for (i = 0; i < write_count; i++) {            printf(" %02X", sysex[i]);        }        printf("\n");        ssize_t count = write(uart0_fd, sysex, write_count);        if (count < 0) {            perror("write in midi_send_sysex");            return;        }        if (count != write_count) {            fprintf(stderr, "midi_send_sysex write didnt write enough bytes\n");            return;        }    }}