recipes-extended/multitech: add set-rs485

Add simple utility to enable RS-485 half-duplex mode for a given tty device

2 files changed, 99 insertions, 0 deletions

diff --git a/recipes-extended/multitech/set-rs485/set-rs485.c b/recipes-extended/multitech/set-rs485/set-rs485.c
new file mode 100644
index 0000000..1e53092
--- /dev/null
+++ b/recipes-extended/multitech/set-rs485/set-rs485.c
@@ -0,0 +1,81 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <termios.h>
+#include <unistd.h>
+#include <sys/ioctl.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <linux/serial.h>
+
+int openserial(char *devicename)
+{
+    int fd;
+
+    if ((fd = open(devicename, O_RDWR)) == -1) {
+        perror("openserial(): open()");
+        return 0;
+    }
+
+    return fd;
+}
+
+int setRS485(int fd, int state)
+{
+    struct serial_rs485 rs485;
+
+    if (ioctl(fd, TIOCGRS485, &rs485) == -1) {
+        perror("TIOCGRS485");
+        return 0;
+    }
+
+    //printf("Old RS485 flags %x\n", rs485.flags);
+
+    if (state)
+        rs485.flags |= SER_RS485_ENABLED;
+    else
+        rs485.flags &= ~SER_RS485_ENABLED;
+
+    if (ioctl(fd, TIOCSRS485, &rs485) == -1) {
+        perror("TIOCSRS485");
+        return 0;
+    }
+
+    //printf("New RS485 flags %x\n", rs485.flags);
+
+    return 1;
+}
+
+int main(int argc, char *argv[])
+{
+    int fd;
+
+    if (argc != 3) {
+        printf("Usage: set_rs485hd tty 0|1\n");
+        return 1;
+    }
+
+    char *serialdev = argv[1];
+    char *state_str = argv[2];
+
+    int state = atoi(state_str);
+
+    fd = openserial(serialdev);
+    if (!fd) {
+        fprintf(stderr, "Error while initializing %s.\n", serialdev);
+        return 1;
+    }
+
+    printf("%s: setting RS485 to ", serialdev);
+
+    if (state)
+        printf("%s\n", "enabled");
+    else
+        printf("%s\n", "disabled");
+
+    if (setRS485(fd, state))
+        return 0;
+    else
+        return 1;
+}
+
diff --git a/recipes-extended/multitech/set-rs485_0.1.bb b/recipes-extended/multitech/set-rs485_0.1.bb
new file mode 100644
index 0000000..09fe9f9
--- /dev/null
+++ b/recipes-extended/multitech/set-rs485_0.1.bb
@@ -0,0 +1,18 @@
+DESCRIPTION = "Enables RS485 mode for a serial tty device"
+HOMEPAGE = "http://www.multitech.net/"
+PRIORITY = "optional"
+LICENSE = "GPLv2+"
+LIC_FILES_CHKSUM = "file://${COMMON_LICENSE_DIR}/GPL-2.0;md5=801f80980d171dd6425610833a22dbe6"
+PR = "r0"
+
+SRC_URI = "file://set-rs485.c"
+S = "${WORKDIR}"
+
+do_compile() {
+	${CC} ${CFLAGS} ${LDFLAGS} -o set-rs485 set-rs485.c
+}
+
+do_install() {
+	install -d ${D}${bindir}
+	install -m 0755 set-rs485 ${D}${bindir}/
+}