added a help section about GPIO API, update DE translations

lang/de.php

@@ -266,13 +266,13 @@ return [
 		',
 	'hwtuning.overclock' => 'Auf 160MHz übertakten',
 
-	'gpio2_config' => 'GPIO2 function', // TODO translate
-	'gpio4_config' => 'GPIO4 function',
-	'gpio5_config' => 'GPIO5 function',
-	'gpio_config.off' => 'Disabled',
-	'gpio_config.off_2' => 'Debug UART Tx',
-	'gpio_config.out_initial0' => 'Output (initial 0)',
-	'gpio_config.out_initial1' => 'Output (initial 1)',
+	'gpio2_config' => 'GPIO2 Funktion',
+	'gpio4_config' => 'GPIO4 Funktion',
+	'gpio5_config' => 'GPIO5 Funktion',
+	'gpio_config.off' => 'Deaktiviert',
+	'gpio_config.off_2' => 'UART Tx Debuggen',
+	'gpio_config.out_initial0' => 'Output (Anfangslevel 0)',
+	'gpio_config.out_initial1' => 'Output (Anfangslevel 1)',
 	'gpio_config.in_pull' => 'Input (pull-up)',
 	'gpio_config.in_nopull' => 'Input (floating)',
 

pages/help.php

@@ -18,6 +18,7 @@
 <?php require __DIR__ . "/help/cmd_screen.php"; ?>
 <?php require __DIR__ . "/help/cmd_d2d.php"; ?>
 <?php require __DIR__ . "/help/cmd_system.php"; ?>
+<?php require __DIR__ . "/help/iocontrol.php"; ?>
 
 <script>
 	function hpfold(yes) {

pages/help/iocontrol.php

@@ -0,0 +1,39 @@
+<div class="Box fold">
+	<h2>Remote GPIO Control</h2>
+
+	<div class="Row v">
+		<p>
+			ESPTerm provides a simple API to remotely control and read GPIO pins GPIO2, GPIO4, and GPIO5.
+			The main use of this API is to remotely reset a device that communicates with ESPTerm
+			through the UART.
+		</p>
+		
+		<p>
+			GPIO2 is normally used for debug UART, so when used as GPIO, debug logging is disabled. You
+			can configure the pin functions in <a href="<?= url('cfg_system') ?>">System Settings</a>.
+    </p>
+
+		<p>
+			The GPIO control endpoint is `/api/v1/gpio`, with optional GET arguments:
+		</p>
+
+		<ul>
+			<li>`do2=<i>x</i>` - set GPIO2 level. <i>x</i> can be `0`, `1`, or `t` to toggle the pin.
+			<li>`do4=<i>x</i>` - set GPIO4 level
+			<li>`do5=<i>x</i>` - set GPIO5 level
+			<li>`pulse=<i>ms</i>` - the command starts a pulse. After the given amount of time 
+			  (milliseconds) has elapsed, the pins are set to the opposite levels than what was specified 
+			  (in the case of toggle, the original pin state)
+		</ul>
+
+		<p>
+		  A quick example: <a href="/api/v1/gpio?do4=1&amp;pulse=500">`/api/v1/gpio?do4=1&amp;pulse=500`</a>
+		  sends a 500ms long positive pulse on GPIO4.
+		</p>
+
+		<p>
+			The GPIO endpoint always returns a JSON object like this: `{"io2":0,"io4":1,"io5":0}`, showing
+			the current input levels. Input reading works always, regardless of the GPIO settings.
+		</p>
+	</div>
+</div>