Add experimental RS-485 support

Many modern RS-485 serial devices such as the ones from FTDI already
operate in RS-485 mode by default and will work with tio out of the box.
However, there are some RS-232/485 devices which need to be switched
from e.g. RS-232 to RS-485 mode to operate accordingly on the physical
level.

This commit implements the switching mechanism and interface required to
enable RS-485 mode. It only works on Linux and with serial devices which
use device drivers that support the Linux RS-485 control interface.

The RS-485 feature is detailed via the following options:

 --rs-485                           Enable RS-485 mode
 --rs-485-config <config>           Set RS-485 configuration

Set the RS-485 configuration using the following key or key value pair
format in the configuration field:

 RTS_ON_SEND=value             Set logical level (0 or 1) for RTS pin when sending
 RTS_AFTER_SEND=value          Set logical level (0 or 1) for RTS pin after sending
 RTS_DELAY_BEFORE_SEND=value   Set RTS delay (ms) before sending
 RTS_DELAY_AFTER_SEND=value    Set RTS delay (ms) after sending
 RX_DURING_TX                  Receive data even while sending data

If defining more than one key or key value pair, they must be comma
separated.

Example use:

 $ tio /dev/ttyUSB0 --rs-485 --rs-r485-config=RTS_DELAY_AFTER_SEND=50,RX_DURING_TX

TODO

@@ -29,13 +29,3 @@
     $ tio --socket ws:1234
 
    Use libwesockets to implement feature.
-
- * RS-485 support
-
-   Many modern RS-485 devices such as the ones from FTDI already operate in
-   RS-485 mode by default and will work with tio out of the box. However, there
-   are still some RS-232/485 devices which need to be switched from e.g. RS-232 to
-   RS-485 mode to operate accordingly on the physical level.
-
-   To enable RS-485 mode on such serial devices the idea is to add a --rs-485
-   option.

example/tiorc

@@ -44,3 +44,9 @@ color = 11
 pattern = usb([0-9]*)
 tty = /dev/ttyUSB%s
 color = 12
+
+[rs-485-device]
+tty = /dev/ttyUSB0
+rs-485 = enable
+rs-485-config = RTS_ON_SEND=1,RTS_AFTER_SEND=1,RTS_DELAY_BEFORE_SEND=60,RTS_DELAY_AFTER_SEND=80,RX_DURING_TX
+color = 13

man/tio.1.in

@@ -229,6 +229,33 @@ response mode to make it easy to parse the response.
 
 Set timeout [ms] of line response (default: 100).
 
+.TP
+.BR "    \-\-rs\-485"
+
+Enable RS-485 mode.
+
+.TP
+.BR "    \-\-rs\-485\-config " \fI<config>
+
+Set the RS-485 configuration using the following key or key value pair format in
+the configuration field:
+
+.RS
+.TP 30n
+.IP \fBRTS_ON_SEND=value
+Set logical level (0 or 1) for RTS pin when sending
+.IP \fBRTS_AFTER_SEND=value
+Set logical level (0 or 1) for RTS pin after sending
+.IP \fBRTS_DELAY_BEFORE_SEND=value
+Set RTS delay (ms) before sending
+.IP \fBRTS_DELAY_AFTER_SEND=value
+Set RTS delay (ms) after sending
+.IP \fBRX_DURING_TX
+Receive data even while sending data
+.P
+If defining more than one key or key value pair, they must be comma separated.
+.RE
+
 .TP
 .BR \-v ", " \-\-version
 
@@ -358,6 +385,10 @@ Set prefix ctrl key (a..z, default: t)
 Enable wait for line response
 .IP "\fBresponse-timeout"
 Set line response timeout
+.IP "\fBrs-485"
+Enable RS-485 mode
+.IP "\fBrs-485-config"
+Set RS-485 configuration
 
 .SH "CONFIGURATION FILE EXAMPLES"
 
@@ -507,6 +538,11 @@ Likewise, to pipe data from file to the serial device:
 
 $ cat data.bin | tio /dev/serial/by\-id/usb\-FTDI_TTL232R-3V3_FTGQVXBL\-if00\-port0
 
+.TP
+Enable RS-485 mode:
+
+$ tio --rs-485 --rs-485-config=RTS_ON_SEND=1,RX_DURING_TX /dev/ttyUSB0
+
 .SH "WEBSITE"
 .PP
 Visit https://tio.github.io

meson.build

@@ -71,5 +71,12 @@ foreach rate : test_baudrates
   endif
 endforeach
 
+# Test for RS-485 support on Linux
+if host_machine.system() == 'linux'
+  if compiler.check_header('linux/serial.h')
+    enable_rs485 = compiler.has_header_symbol('sys/ioctl.h', 'TIOCSRS485')
+  endif
+endif
+
 subdir('src')
 subdir('man')

src/bash-completion/tio.in

@@ -31,6 +31,8 @@ _tio()
           -S --socket \
           -r --response-wait \
              --response-timeout \
+             --rs-485 \
+             --rs-485-config \
           -x --hexadecimal \
           -v --version \
           -h --help"
@@ -122,6 +124,14 @@ _tio()
             COMPREPLY=( $(compgen -W "1 10 100" -- ${cur}) )
             return 0
             ;;
+        --rs-485)
+            COMPREPLY=( $(compgen -W "${opts}" -- ${cur}) )
+            return 0
+            ;;
+        --rs-485-config)
+            COMPREPLY=( $(compgen -W "RTS_ON_SEND RTS_AFTER_SEND RTS_DELAY_BEFORE_SEND RTS_DELAY_AFTER_SEND RX_DURING_TX"  -- ${cur}) )
+            return 0
+            ;;
         -x | --hexadecimal)
             COMPREPLY=( $(compgen -W "${opts}" -- ${cur}) )
             return 0

src/configfile.c

@@ -42,6 +42,7 @@
 #include "options.h"
 #include "error.h"
 #include "print.h"
+#include "rs485.h"
 
 static struct config_t *c;
 
@@ -264,6 +265,22 @@ static int data_handler(void *user, const char *section, const char *name,
         {
             option.response_timeout = atoi(value);
         }
+        else if (!strcmp(name, "rs-485"))
+        {
+            if (!strcmp(value, "enable"))
+            {
+                option.rs485 = true;
+            }
+            else if (!strcmp(value, "disable"))
+            {
+                option.rs485 = false;
+            }
+        }
+        else if (!strcmp(name, "rs-485-config"))
+        {
+            rs485_parse_config(value);
+        }
+
     }
     return 0;
 }

src/meson.build

@@ -14,7 +14,8 @@ tio_sources = [
   'configfile.c',
   'signals.c',
   'socket.c',
-  'setspeed.c'
+  'setspeed.c',
+  'rs485.c'
 ]
 
 tio_dep = dependency('inih', required: true,
@@ -31,6 +32,10 @@ if enable_iossiospeed
   tio_c_args += '-DHAVE_IOSSIOSPEED'
 endif
 
+if enable_rs485
+  tio_c_args += '-DHAVE_RS485'
+endif
+
 executable('tio',
   tio_sources,
   c_args: tio_c_args,

src/options.c

@@ -35,6 +35,7 @@
 #include "misc.h"
 #include "print.h"
 #include "tty.h"
+#include "rs485.h"
 
 enum opt_t
 {
@@ -44,6 +45,8 @@ enum opt_t
     OPT_LOG_STRIP,
     OPT_LINE_PULSE_DURATION,
     OPT_RESPONSE_TIMEOUT,
+    OPT_RS485,
+    OPT_RS485_CONFIG,
 };
 
 /* Default options */
@@ -78,6 +81,10 @@ struct option_t option =
     .response_wait = false,
     .response_timeout = 100,
     .mute = false,
+    .rs485 = false,
+    .rs485_config_flags = 0,
+    .rs485_delay_rts_before_send = -1,
+    .rs485_delay_rts_after_send = -1,
 };
 
 void print_help(char *argv[])
@@ -109,6 +116,8 @@ void print_help(char *argv[])
     printf("  -x, --hexadecimal                      Enable hexadecimal mode\n");
     printf("  -r, --response-wait                    Wait for line response then quit\n");
     printf("      --response-timeout <ms>            Response timeout (default: 100)\n");
+    printf("      --rs-485                           Enable RS-485 mode\n");
+    printf("      --rs-485-config <config>           Set RS-485 configuration\n");
     printf("  -v, --version                          Display version\n");
     printf("  -h, --help                             Display help\n");
     printf("\n");
@@ -295,6 +304,8 @@ void options_parse(int argc, char *argv[])
             {"hexadecimal",         no_argument,       0, 'x'                    },
             {"response-wait",       no_argument,       0, 'r'                    },
             {"response-timeout",    required_argument, 0, OPT_RESPONSE_TIMEOUT   },
+            {"rs-485",              no_argument,       0, OPT_RS485              },
+            {"rs-485-config",       required_argument, 0, OPT_RS485_CONFIG       },
             {"version",             no_argument,       0, 'v'                    },
             {"help",                no_argument,       0, 'h'                    },
             {0,                     0,                 0,  0                     }
@@ -437,6 +448,14 @@ void options_parse(int argc, char *argv[])
                 option.response_timeout = string_to_long(optarg);
                 break;
 
+            case OPT_RS485:
+                option.rs485 = true;
+                break;
+
+            case OPT_RS485_CONFIG:
+                rs485_parse_config(optarg);
+                break;
+
             case 'v':
                 printf("tio v%s\n", VERSION);
                 exit(EXIT_SUCCESS);

src/options.h

@@ -21,6 +21,7 @@
 
 #pragma once
 
+#include <stdint.h>
 #include <stdbool.h>
 #include <limits.h>
 #include <termios.h>
@@ -70,6 +71,10 @@ struct option_t
     bool response_wait;
     int response_timeout;
     bool mute;
+    bool rs485;
+    uint32_t rs485_config_flags;
+    int32_t rs485_delay_rts_before_send;
+    int32_t rs485_delay_rts_after_send;
 };
 
 extern struct option_t option;

src/print.h

@@ -21,6 +21,7 @@
 
 #pragma once
 
+#include <stdio.h>
 #include <stdbool.h>
 #include "misc.h"
 #include "error.h"