drivers/tripplitesu.c: add 1s delay in command_send

NEWS.adoc

@@ -204,6 +204,10 @@ https://github.com/networkupstools/nut/milestone/12
      PR #3093]
    * Fixed default `unit_id`, apparently broken by changes in NUT v2.8.1.
      [issue #3191, PR #3192]
+
+ - `tripplitesu` driver updates:
+   * Added configurable command delay to prevent read timeouts
+     [PR #3273]
 
  - Introduced a new NUT driver named `nut-upower` which provides support
    for monitoring UPS and battery devices managed by the UPower daemon

data/driver.list.in

@@ -1569,6 +1569,7 @@
 "Tripp Lite"	"ups"	"3"	"SU3000XLCD"	"USB (protocol 4004)"	"usbhid-ups"	# http://www.tripplite.com/en/products/model.cfm?txtSeriesID=744&txtModelID=5342
 "Tripp Lite"	"ups"	"3"	"SUINT1000RTXL2UA"	"USB (protocol 4001)"	"usbhid-ups"	# http://www.tripplite.com/en/products/model.cfm?txtModelID=3983
 "Tripp Lite"	"ups"	"3"	"SUINT1500RTXL2UA"	"USB (protocol 4001)"	"usbhid-ups"	# http://www.tripplite.com/en/products/model.cfm?txtSeriesID=934&txtModelID=2720
+"Tripp Lite"	"ups"	"3"	"SUINT1500RTXL2UA"	"Serial"	"tripplitesu"	# http://www.tripplite.com/en/products/model.cfm?txtSeriesID=934&txtModelID=2720
 "Tripp Lite"	"ups"	"3"	"SUINT2200RTXL2UA"	"USB (protocol 4001)"	"usbhid-ups"	# http://www.tripplite.com/en/products/model.cfm?txtSeriesID=934&txtModelID=3970
 "Tripp Lite"	"ups"	"3"	"SUINT3000RTXL2U"	"USB (protocol 4005)"	"usbhid-ups"	# http://www.tripplite.com/en/products/model.cfm?txtModelID=4523
 

docs/man/tripplitesu.txt

@@ -33,6 +33,15 @@ Set the low battery warning threshold in percent at which shutdown is
 initiated by linkman:upsmon[8].  By default, the UPS may not report low battery
 until there are only a few seconds left.  Common values are around 25--30.
 
+*command_delay*='milliseconds'::
+Set a delay in milliseconds to be applied before each command sent to the UPS.
+The default value is 0 (disabled). If experiencing intermittent communication
+timeouts when multiple commands are sent in rapid succession, set this to
+1000 (1 second) or adjust as needed.
+
+This delay helps prevent "read timeout" errors when the hardware buffer is
+not ready to accept new commands immediately after completing the previous one.
+
 AUTHOR
 ------
 

drivers/tripplitesu.c

@@ -66,6 +66,7 @@
 
    The following parameters (ups.conf) are supported:
 	lowbatt
+	command_delay
 
    The following variables are supported (RW = read/write):
 	ambient.humidity (1)
@@ -126,7 +127,7 @@
 #include "nut_stdint.h"
 
 #define DRIVER_NAME	"Tripp Lite SmartOnline driver"
-#define DRIVER_VERSION	"0.11"
+#define DRIVER_VERSION	"0.12"
 
 /* driver description structure */
 upsdrv_info_t upsdrv_info = {
@@ -163,6 +164,8 @@ static struct {
 	unsigned long commands_available;
 } ups;
 
+static long command_delay = 0; /* delay in milliseconds before each command, 0 = no delay by default */
+
 /* bits in commands_available */
 #define WDG_AVAILABLE            (1UL <<  1)
 
@@ -224,6 +227,11 @@ static ssize_t do_command(char type, const char *command, const char *parameters
 
 	ser_flush_io(upsfd);
 
+	/* Apply configurable delay if enabled (> 0) to prevent communication timeouts */
+	if (command_delay > 0) {
+		usleep((useconds_t)command_delay*1000);
+	}
+
 	if (response) {
 		*response = '\0';
 	}
@@ -890,12 +898,35 @@ void upsdrv_tweak_prognames(void)
 void upsdrv_makevartable(void)
 {
 	addvar(VAR_VALUE, "lowbatt", "Set low battery level, in percent");
+	addvar(VAR_VALUE, "command_delay", 
+		"Delay in milliseconds before each command (default: 0 = no delay; "
+		"set to 1000ms if experiencing communication timeouts)");
 }
 
 void upsdrv_initups(void)
 {
+	const char *val;
+
 	upsfd = ser_open(device_path);
 	ser_set_speed(upsfd, device_path, B2400);
+
+	/* Initialize command_delay from configuration */
+	val = getval("command_delay");
+	if (val) {
+		long temp = atol(val);
+		/* 0 (no delay) or positive values */
+		if (temp < 0) {
+			fatalx(EXIT_FAILURE, "Invalid command_delay parameter: %s (must be >= 0)", val);
+		}
+		command_delay = temp;
+		if (command_delay == 0) {
+			upsdebugx(2, "command_delay is explicitly set to 0 (no delay)");
+		} else {
+			upsdebugx(2, "Setting command_delay to %ld milliseconds", command_delay);
+		}
+	} else {
+		upsdebugx(2, "Using default command_delay of %ld (no delay)", command_delay);
+	}
 }
 
 void upsdrv_cleanup(void)