LuPPC/src/c/serial.c

#include "lupi.h"
#include <lua.h>
#include <lualib.h>
#include <lauxlib.h>
#include <stdio.h>
#include <stdlib.h>
#include <dirent.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <termios.h>
#include <sys/stat.h>

int s_listports(lua_State * L) {
	DIR * d = opendir("/sys/class/tty");
	struct dirent * ent = NULL;
	struct stat statbuf;
	char path[255];
	char linkpath[255];
	lua_newtable(L);
	size_t index = 1;
	while ((ent = readdir(d)) != NULL) {
		sprintf(path, "/sys/class/tty/%s/device", ent->d_name);
		if (stat(path, &statbuf) == 0) {
			readlink(path, linkpath, 255);
			if (strstr(linkpath, "serial8250") == NULL) {
				// We have a serial port
				lua_pushinteger(L, index);
				lua_pushstring(L, ent->d_name);
				lua_settable(L, -3);
			}
		}
	}
	return 1;
}

struct baudrate {
	uint32_t baud;
	tcflag_t flags;
};

// taken from here: https://man7.org/linux/man-pages/man3/termios.3.html
struct baudrate baudrates[] = {
	{0, B0},
	{50, B50},
	{75, B75},
	{110, B110},
	{134, B134},
	{150, B150},
	{200, B200},
	{300, B300},
	{600, B600},
	{1200, B1200},
	{1800, B1800},
	{2400, B2400},
	{4800, B4800},
	{9600, B9600},
	{19200, B19200},
	{38400, B38400},
	{57600, B57600},
	{115200, B115200},
	{230400, B230400}
};

struct baudrate * getbaud(uint32_t baud) {
	for (size_t i=0; i<sizeof(baudrates)/sizeof(struct baudrate); ++i) {
		if (baudrates[i].baud == baud) {
			return &baudrates[i];
		} else if (baudrates[i].baud > baud) {
			return &baudrates[i-1];
		}
	}
	return getbaud(230400);
}

struct sport {
	uint32_t baudrate;
	int fd;
	struct termios options;
};

int s_openport(lua_State * L) {
	char * path = luaL_checkstring(L, 1);
	struct sport * port = lua_newuserdata(L, sizeof(struct sport));
	port->baudrate = 9600;
	char rpath[255];
	sprintf(rpath, "/dev/%s", path);
	port->fd = open(rpath, O_RDWR | O_NOCTTY | O_NDELAY | O_NONBLOCK);
	if (port->fd == -1)
		luaL_error(L, "unable to open port %s: ", path, strerror(errno));
	tcgetattr(port->fd, &port->options);
	cfsetispeed(&port->options, B9600);
	cfsetospeed(&port->options, B9600);
	tcsetattr(port->fd, TCSANOW, &port->options);
	return 1;
}

int s_setbaudrate(lua_State * L) {
	struct sport * port = lua_touserdata(L, 1);
	long raw_br = luaL_checkinteger(L, 2);
	struct baudrate * br = getbaud(raw_br & 0xFFFFFFFF);
	//port->options.c_cflag &= ~(CBAUD);
	//port->options.c_cflag |= br->flags;
	cfsetispeed(&port->options, br->flags);
	cfsetospeed(&port->options, br->flags);
	port->baudrate = br->baud;
	lua_pushinteger(L, br->baud);
	port->options.c_cflag &= ~PARENB;
	port->options.c_cflag &= ~CSTOPB;
	port->options.c_cflag &= ~CSIZE;
	port->options.c_cflag |= CS8;
	tcsetattr(port->fd, TCSANOW, &port->options);
	return 1;
}

int s_getbaudrate(lua_State * L) {
	struct sport * port = lua_touserdata(L, 1);
	lua_pushinteger(L, port->baudrate);
	return 1;
}

int s_write(lua_State * L) {
	struct sport * port = lua_touserdata(L, 1);
	size_t len = 0;
	char * data = luaL_checklstring(L, 2, &len);
	size_t ioc = 0;
	if ((ioc = write(port->fd, data, len)) != len) {
		luaL_error(L, "io error! %llu != %llu", ioc, len);
	}
	return 0;
}

int s_read(lua_State * L) {
	struct sport * port = lua_touserdata(L, 1);
	char buffer[2048]; // Max packet size
	long size = luaL_checkinteger(L, 2);
	size_t ioc = read(port->fd, buffer, size);
	if (ioc != size && ioc != 0) {
		luaL_error(L, "io error! %llu != %llu or 0", ioc, size);
	} else if (ioc != 0) {
		lua_pushlstring(L, buffer, size);
		return 1;
	}
	return 0;	
}

void serial_start(lua_State * L) {
	struct luaL_Reg seriallib[] = {
		{"open", s_openport},
		{"list", s_listports},
		{"write", s_write},
		{"read", s_read},
		{"setbaud", s_setbaudrate},
		{"getbaud", s_getbaudrate},
		{NULL, NULL}
	};
	luaL_openlib(L, "serial", seriallib, 0);
}