Address 3 different start scenarios 1st lay cal + MMU

This PR tries to address the 3 different startup scenarios for 1st layer calibration with the MMU:

- 1st lay cal started with correct filament already loaded in the nozzle - we should continue, but skip the first 58mm (first 2 g-codes in the hard coded sequence) of purge line extrusion
- 1st lay cal started with other filament already loaded in the nozzle - we should unload and then issue a toolchange with no extra unload
- 1st lay cal started without loaded filament - we should just do a toolchange with no extra unload

PFW-1457

Firmware/first_lay_cal.cpp

@@ -32,21 +32,39 @@ void lay1cal_wait_preheat()
 //! @brief Load filament
 //! @param cmd_buffer character buffer needed to format gcodes
 //! @param filament filament to use (applies for MMU only)
-void lay1cal_load_filament(char *cmd_buffer, uint8_t filament)
+//! @returns true if extra purge distance is needed in case of MMU prints (after a toolchange), otherwise false
+bool lay1cal_load_filament(char *cmd_buffer, uint8_t filament)
 {
     if (MMU2::mmu2.Enabled())
     {
         enquecommand_P(PSTR("M83"));
         enquecommand_P(PSTR("G1 Y-3.0 F1000.0"));
         enquecommand_P(PSTR("G1 Z0.4 F1000.0"));
-        sprintf_P(cmd_buffer, PSTR("T%d"), filament);
-        enquecommand(cmd_buffer);
-    }
 
+        uint8_t currentTool = MMU2::mmu2.get_current_tool();
+        if(currentTool == filament ){
+            // already have the correct tool loaded - do nothing
+            return false;
+        } else if( currentTool != (uint8_t)MMU2::FILAMENT_UNKNOWN){
+            // some other slot is loaded, perform an unload first
+            enquecommand_P(PSTR("M702"));
+        }
+        // perform a toolchange
+        // sprintf_P(cmd_buffer, PSTR("T%d"), filament);
+        // rewriting the trivial T<filament> g-code command saves 30B:
+        cmd_buffer[0] = 'T';
+        cmd_buffer[1] = filament + '0';
+        cmd_buffer[2] = 0;
+
+        enquecommand(cmd_buffer);
+        return true;
+    }
+    return false;
 }
 
 //! @brief Print intro line
-void lay1cal_intro_line()
+//! @param extraPurgeNeeded false if the first MMU-related "G1 E29" have to be skipped because the nozzle is already full of filament
+void lay1cal_intro_line(bool extraPurgeNeeded)
 {
     static const char cmd_intro_mmu_3[] PROGMEM = "G1 X55.0 E29.0 F1073.0";
     static const char cmd_intro_mmu_4[] PROGMEM = "G1 X5.0 E29.0 F1800.0";
@@ -61,8 +79,10 @@ void lay1cal_intro_line()
 
     static const char * const intro_mmu_cmd[] PROGMEM =
     {
+        // first 2 items are only relevant if filament was not loaded - i.e. extraPurgeNeeded == true
         cmd_intro_mmu_3,
         cmd_intro_mmu_4,
+
         cmd_intro_mmu_5,
         cmd_intro_mmu_6,
         cmd_intro_mmu_7,
@@ -75,7 +95,7 @@ void lay1cal_intro_line()
 
     if (MMU2::mmu2.Enabled())
     {
-        for (uint8_t i = 0; i < (sizeof(intro_mmu_cmd)/sizeof(intro_mmu_cmd[0])); ++i)
+        for (uint8_t i = (extraPurgeNeeded ? 0 : 2); i < (sizeof(intro_mmu_cmd)/sizeof(intro_mmu_cmd[0])); ++i)
         {
             enquecommand_P(static_cast<char*>(pgm_read_ptr(&intro_mmu_cmd[i])));
         }

Firmware/first_lay_cal.h

@@ -7,8 +7,8 @@
 #include <stdint.h>
 
 void lay1cal_wait_preheat();
-void lay1cal_load_filament(char *cmd_buffer, uint8_t filament);
-void lay1cal_intro_line();
+[[nodiscard]] bool lay1cal_load_filament(char *cmd_buffer, uint8_t filament);
+void lay1cal_intro_line(bool skipExtraPurge);
 void lay1cal_before_meander();
 void lay1cal_meander(char *cmd_buffer);
 void lay1cal_square(char *cmd_buffer, uint8_t i);

Firmware/mmu2.cpp

@@ -7,6 +7,7 @@
 #include "mmu2_progress_converter.h"
 #include "mmu2_reporting.h"
 
+#include "cardreader.h" // for IS_SD_PRINTING
 #include "Marlin.h"
 #include "language.h"
 #include "messages.h"
@@ -334,7 +335,10 @@ bool MMU2::tool_change(uint8_t slot) {
         return false;
 
     if (slot != extruder) {
-        if (FindaDetectsFilament()) {
+        if (/*FindaDetectsFilament()*/
+            /*!IS_SD_PRINTING && !usb_timer.running()*/
+            ! printer_active()
+            ) {
             // If Tcodes are used manually through the serial
             // we need to unload manually as well -- but only if FINDA detects filament
             unload();
@@ -385,7 +389,7 @@ void MMU2::get_statistics() {
     logic.Statistics();
 }
 
-uint8_t MMU2::get_current_tool() const {
+uint8_t __attribute__((noinline)) MMU2::get_current_tool() const {
     return extruder == MMU2_NO_TOOL ? (uint8_t)FILAMENT_UNKNOWN : extruder;
 }
 

Firmware/ultralcd.cpp

@@ -68,6 +68,7 @@ int8_t FSensorStateMenu = 1;
 
 LcdCommands lcd_commands_type = LcdCommands::Idle;
 static uint8_t lcd_commands_step = 0;
+static bool extraPurgeNeeded = false; ///< lcd_commands - detect if extra purge after MMU-toolchange is necessary or not
 
 CustomMsg custom_message_type = CustomMsg::Status;
 uint8_t custom_message_state = 0;
@@ -874,14 +875,14 @@ void lcd_commands()
                 lcd_commands_step = 10;
                 break;
             case 10:
-                lay1cal_load_filament(cmd1, lay1cal_filament);
+                extraPurgeNeeded = lay1cal_load_filament(cmd1, lay1cal_filament);
                 lcd_commands_step = 9;
                 break;
             case 9:
                 lcd_clear();
                 menu_depth = 0;
                 menu_submenu(lcd_babystep_z);
-                lay1cal_intro_line();
+                lay1cal_intro_line(extraPurgeNeeded);
                 lcd_commands_step = 8;
                 break;
             case 8: