Improve Skydimo SK0L32 serial device support

Controllers/SkydimoSerialController/RGBController_SkydimoSerial.cpp

@@ -11,6 +11,11 @@
 
 #include "RGBController_SkydimoSerial.h"
 
+using namespace std::chrono_literals;
+
+#define SKYDIMO_SERIAL_SLEEP_THRESHOLD 100ms
+#define SKYDIMO_SERIAL_KEEPALIVE_PERIOD 1500ms
+
 /**------------------------------------------------------------------*\
     @name Skydimo Serial
     @category LEDStrip
@@ -41,12 +46,19 @@ RGBController_SkydimoSerial::RGBController_SkydimoSerial(SkydimoSerialController
     modes.push_back(direct_mode);
 
     SetupZones();
+
+    last_update_time    = std::chrono::steady_clock::now();
+    keepalive_thread_run = true;
+    keepalive_thread    = std::thread(&RGBController_SkydimoSerial::KeepaliveThreadFunction, this);
 }
 
 RGBController_SkydimoSerial::~RGBController_SkydimoSerial()
 {
     Shutdown();
 
+    keepalive_thread_run = false;
+    keepalive_thread.join();
+
     controller->SetBlack();
     delete controller;
 }
@@ -129,6 +141,8 @@ void RGBController_SkydimoSerial::DeviceConfigureZone(int zone_idx)
 
 void RGBController_SkydimoSerial::DeviceUpdateLEDs()
 {
+    last_update_time = std::chrono::steady_clock::now();
+
     controller->SetLEDs(colors);
 }
 
@@ -145,3 +159,29 @@ void RGBController_SkydimoSerial::DeviceUpdateSingleLED(int)
 void RGBController_SkydimoSerial::DeviceUpdateMode()
 {
 }
+
+void RGBController_SkydimoSerial::KeepaliveThreadFunction()
+{
+    std::chrono::nanoseconds sleep_time;
+
+    while(keepalive_thread_run.load())
+    {
+        sleep_time = SKYDIMO_SERIAL_KEEPALIVE_PERIOD
+                   - (std::chrono::steady_clock::now() - last_update_time);
+
+        if(sleep_time <= SKYDIMO_SERIAL_SLEEP_THRESHOLD)
+        {
+            /*-----------------------------------------------------*\
+            | SK0L32 turns its output off when it does not receive  |
+            | a frame for a short period. Repeat the current frame  |
+            | while the device is connected, like the vendor app.  |
+            \*-----------------------------------------------------*/
+            UpdateLEDsInternal();   // Already protected through the device update thread
+            std::this_thread::sleep_for(SKYDIMO_SERIAL_KEEPALIVE_PERIOD);
+        }
+        else
+        {
+            std::this_thread::sleep_for(sleep_time);
+        }
+    }
+}

Controllers/SkydimoSerialController/RGBController_SkydimoSerial.h

@@ -11,6 +11,8 @@
 
 #pragma once
 
+#include <chrono>
+#include <thread>
 #include "RGBController.h"
 #include "SkydimoSerialController.h"
 
@@ -28,6 +30,11 @@ public:
     void        DeviceUpdateSingleLED(int led);
     void        DeviceUpdateMode();
 
+    void        KeepaliveThreadFunction();
+
 private:
-    SkydimoSerialController* controller;
+    SkydimoSerialController*                                  controller;
+    std::chrono::time_point<std::chrono::steady_clock>         last_update_time;
+    std::atomic<bool>                                          keepalive_thread_run;
+    std::thread                                                keepalive_thread;
 };

Controllers/SkydimoSerialController/SkydimoSerialController.cpp

@@ -436,8 +436,15 @@ bool SkydimoSerialController::WriteFrame(const std::vector<RGBColor>& colors, un
         packet.push_back(skydimo_serial_frame_header[header_idx]);
     }
 
-    packet.push_back((unsigned char)((count >> 8) & 0xFF));
-    packet.push_back((unsigned char)(count & 0xFF));
+    /*-----------------------------------------------------*\
+    | Skydimo uses the Adalight length convention: the      |
+    | 16-bit field contains the last LED index, not the     |
+    | number of LEDs.                                       |
+    \*-----------------------------------------------------*/
+    unsigned int frame_length = count > 0 ? count - 1 : 0;
+
+    packet.push_back((unsigned char)((frame_length >> 8) & 0xFF));
+    packet.push_back((unsigned char)(frame_length & 0xFF));
 
     for(unsigned int led_idx = 0; led_idx < count; led_idx++)
     {