Fix axis char printing

Marlin/src/core/serial.h

 typedef struct SerialChar { char c; SerialChar(char n) : c(n) { } } serial_char_t;
 inline void SERIAL_ECHO(serial_char_t x) { SERIAL_IMPL.write(x.c); }
 #define AS_CHAR(C) serial_char_t(C)
+#define AS_DIGIT(C) AS_CHAR('0' + (C))
 
 // SERIAL_ECHO_F prints a floating point value with optional precision
 inline void SERIAL_ECHO_F(EnsureDouble x, int digit=2) { SERIAL_IMPL.print(x, digit); }

Marlin/src/feature/fwretract.cpp

 
   /* // debugging
     SERIAL_ECHOLNPAIR(
-      "retracting ", retracting,
+      "retracting ", AS_DIGIT(retracting),
       " swapping ", swapping,
       " active extruder ", active_extruder
     );
     LOOP_L_N(i, EXTRUDERS) {
-      SERIAL_ECHOLNPAIR("retracted[", i, "] ", retracted[i]);
+      SERIAL_ECHOLNPAIR("retracted[", i, "] ", AS_DIGIT(retracted[i]));
       #if HAS_MULTI_EXTRUDER
-        SERIAL_ECHOLNPAIR("retracted_swap[", i, "] ", retracted_swap[i]);
+        SERIAL_ECHOLNPAIR("retracted_swap[", i, "] ", AS_DIGIT(retracted_swap[i]));
       #endif
     }
     SERIAL_ECHOLNPAIR("current_position.z ", current_position.z);
   #endif
 
   /* // debugging
-    SERIAL_ECHOLNPAIR("retracting ", retracting);
-    SERIAL_ECHOLNPAIR("swapping ", swapping);
+    SERIAL_ECHOLNPAIR("retracting ", AS_DIGIT(retracting));
+    SERIAL_ECHOLNPAIR("swapping ", AS_DIGIT(swapping));
     SERIAL_ECHOLNPAIR("active_extruder ", active_extruder);
     LOOP_L_N(i, EXTRUDERS) {
-      SERIAL_ECHOLNPAIR("retracted[", i, "] ", retracted[i]);
+      SERIAL_ECHOLNPAIR("retracted[", i, "] ", AS_DIGIT(retracted[i]));
       #if HAS_MULTI_EXTRUDER
-        SERIAL_ECHOLNPAIR("retracted_swap[", i, "] ", retracted_swap[i]);
+        SERIAL_ECHOLNPAIR("retracted_swap[", i, "] ", AS_DIGIT(retracted_swap[i]));
       #endif
     }
     SERIAL_ECHOLNPAIR("current_position.z ", current_position.z);
 
   void FWRetract::M209_report(const bool forReplay/*=false*/) {
     if (!forReplay) { SERIAL_ECHO_MSG("; Auto-Retract: S=0 to disable, 1 to interpret E-only moves as retract/recover"); SERIAL_ECHO_START(); }
-    SERIAL_ECHOLNPAIR("  M209 S", autoretract_enabled);
+    SERIAL_ECHOLNPAIR("  M209 S", AS_DIGIT(autoretract_enabled));
   }
 
 #endif // FWRETRACT_AUTORETRACT

Marlin/src/feature/powerloss.cpp

         DEBUG_ECHOLNPAIR("sd_filename: ", info.sd_filename);
         DEBUG_ECHOLNPAIR("sdpos: ", info.sdpos);
         DEBUG_ECHOLNPAIR("print_job_elapsed: ", info.print_job_elapsed);
-        DEBUG_ECHOLNPAIR("dryrun: ", info.flag.dryrun);
+        DEBUG_ECHOLNPAIR("dryrun: ", AS_DIGIT(info.flag.dryrun));
         DEBUG_ECHOLNPAIR("allow_cold_extrusion: ", info.flag.allow_cold_extrusion);
       }
       else

Marlin/src/gcode/calibrate/M666.cpp

       if (parser.seen(XYZ_CHAR(i))) {
         const float v = parser.value_linear_units();
         if (v * Z_HOME_DIR <= 0) delta_endstop_adj[i] = v;
-        if (DEBUGGING(LEVELING)) DEBUG_ECHOLNPAIR("delta_endstop_adj[", XYZ_CHAR(i), "] = ", delta_endstop_adj[i]);
+        if (DEBUGGING(LEVELING)) DEBUG_ECHOLNPAIR("delta_endstop_adj[", AS_CHAR(XYZ_CHAR(i)), "] = ", delta_endstop_adj[i]);
       }
     }
   }

Marlin/src/gcode/control/M605.cpp

 
         HOTEND_LOOP() {
           DEBUG_ECHOPAIR_P(SP_T_STR, e);
-          LOOP_XYZ(a) DEBUG_ECHOPAIR("  hotend_offset[", e, "].", XYZ_CHAR(a) | 0x20, "=", hotend_offset[e][a]);
+          LOOP_XYZ(a) DEBUG_ECHOPAIR("  hotend_offset[", e, "].", AS_CHAR(XYZ_CHAR(a) | 0x20), "=", hotend_offset[e][a]);
           DEBUG_EOL();
         }
         DEBUG_EOL();

Marlin/src/gcode/parser.cpp

 
       #if ENABLED(DEBUG_GCODE_PARSER)
         if (debug) {
-          SERIAL_ECHOPAIR("Got param ", param, " at index ", p - command_ptr - 1);
+          SERIAL_ECHOPAIR("Got param ", AS_CHAR(param), " at index ", p - command_ptr - 1);
           if (has_val) SERIAL_ECHOPGM(" (has_val)");
         }
       #endif

Marlin/src/lcd/extui/lib/anycubic_chiron/chiron_tft.cpp

           float newposition = atof(&panel_command[6]);
 
           #if ACDEBUG(AC_ACTION)
-            SERIAL_ECHOLNPAIR("Nudge ", panel_command[4], " axis ", newposition);
+            SERIAL_ECHOLNPAIR("Nudge ", AS_CHAR(panel_command[4]), " axis ", newposition);
           #endif
 
           switch (panel_command[4]) {

Marlin/src/lcd/extui/lib/dgus/fysetc/DGUSScreenHandler.cpp

 
   if (!movevalue) {
     // homing
-    DEBUG_ECHOPAIR(" homing ", axiscode);
+    DEBUG_ECHOPAIR(" homing ", AS_CHAR(axiscode));
     char buf[6] = "G28 X";
     buf[4] = axiscode;
     //DEBUG_ECHOPAIR(" ", buf);
   }
   else {
     // movement
-    DEBUG_ECHOPAIR(" move ", axiscode);
+    DEBUG_ECHOPAIR(" move ", AS_CHAR(axiscode));
     bool old_relative_mode = relative_mode;
     if (!relative_mode) {
       //DEBUG_ECHOPGM(" G91");
   return;
 
   cannotmove:
-    DEBUG_ECHOLNPAIR(" cannot move ", axiscode);
+    DEBUG_ECHOLNPAIR(" cannot move ", AS_CHAR(axiscode));
     return;
 }
 

Marlin/src/lcd/extui/lib/dgus/hiprecy/DGUSScreenHandler.cpp

 
   if (!movevalue) {
     // homing
-    DEBUG_ECHOPAIR(" homing ", axiscode);
+    DEBUG_ECHOPAIR(" homing ", AS_CHAR(axiscode));
     char buf[6] = "G28 X";
     buf[4] = axiscode;
     //DEBUG_ECHOPAIR(" ", buf);
   }
   else {
     // movement
-    DEBUG_ECHOPAIR(" move ", axiscode);
+    DEBUG_ECHOPAIR(" move ", AS_CHAR(axiscode));
     bool old_relative_mode = relative_mode;
     if (!relative_mode) {
       //DEBUG_ECHOPGM(" G91");
   return;
 
   cannotmove:
-    DEBUG_ECHOLNPAIR(" cannot move ", axiscode);
+    DEBUG_ECHOLNPAIR(" cannot move ", AS_CHAR(axiscode));
     return;
 }
 

Marlin/src/lcd/extui/lib/dgus/mks/DGUSScreenHandler.cpp

 
   if (!movevalue) {
     // homing
-    DEBUG_ECHOPAIR(" homing ", axiscode);
+    DEBUG_ECHOPAIR(" homing ", AS_CHAR(axiscode));
     // char buf[6] = "G28 X";
     // buf[4] = axiscode;
 
   else if (movevalue == 5) {
     DEBUG_ECHOPAIR("send M84");
     char buf[6];
-    snprintf_P(buf,6,PSTR("M84 %c"),axiscode);
+    snprintf_P(buf,6,PSTR("M84 %c"), axiscode);
     queue.enqueue_one_now(buf);
     ForceCompleteUpdate();
     return;
   }
   else {
     // movement
-    DEBUG_ECHOPAIR(" move ", axiscode);
+    DEBUG_ECHOPAIR(" move ", AS_CHAR(axiscode));
     bool old_relative_mode = relative_mode;
 
     if (!relative_mode) {
   return;
 
   cannotmove:
-    DEBUG_ECHOLNPAIR(" cannot move ", axiscode);
+    DEBUG_ECHOLNPAIR(" cannot move ", AS_CHAR(axiscode));
     return;
 }
 

Marlin/src/lcd/extui/lib/dgus/origin/DGUSScreenHandler.cpp

 
   if (!movevalue) {
     // homing
-    DEBUG_ECHOPAIR(" homing ", axiscode);
+    DEBUG_ECHOPAIR(" homing ", AS_CHAR(axiscode));
     char buf[6] = "G28 X";
     buf[4] = axiscode;
     //DEBUG_ECHOPAIR(" ", buf);
   }
   else {
     // movement
-    DEBUG_ECHOPAIR(" move ", axiscode);
+    DEBUG_ECHOPAIR(" move ", AS_CHAR(axiscode));
     bool old_relative_mode = relative_mode;
     if (!relative_mode) {
       //DEBUG_ECHOPGM(" G91");
   return;
 
   cannotmove:
-    DEBUG_ECHOLNPAIR(" cannot move ", axiscode);
+    DEBUG_ECHOLNPAIR(" cannot move ", AS_CHAR(axiscode));
     return;
 }
 

Marlin/src/lcd/extui/lib/nextion/nextion_tft.cpp

     #if NEXDEBUG(N_SOME)
       uint8_t req = atoi(&nextion_command[1]);
       if (req > 7 && req != 20)
-        DEBUG_ECHOLNPAIR(  "> ", nextion_command[0],
-                         "\n> ", nextion_command[1],
-                         "\n> ", nextion_command[2],
-                         "\n> ", nextion_command[3],
+        DEBUG_ECHOLNPAIR(  "> ", AS_CHAR(nextion_command[0]),
+                         "\n> ", AS_CHAR(nextion_command[1]),
+                         "\n> ", AS_CHAR(nextion_command[2]),
+                         "\n> ", AS_CHAR(nextion_command[3]),
                          "\nprinter_state:", printer_state);
     #endif
   }

Marlin/src/lcd/marlinui.cpp

         // For Cartesian / Core motion simply move to the current_position
         planner.buffer_line(current_position, fr_mm_s, axis == E_AXIS ? e_index : active_extruder);
 
-        //SERIAL_ECHOLNPAIR("Add planner.move with Axis ", axis, " at FR ", fr_mm_s);
+        //SERIAL_ECHOLNPAIR("Add planner.move with Axis ", AS_CHAR(axis_codes[axis]), " at FR ", fr_mm_s);
 
         axis = NO_AXIS;
 
     #endif
     start_time = millis() + (menu_scale < 0.99f ? 0UL : 250UL); // delay for bigger moves
     axis = move_axis;
-    //SERIAL_ECHOLNPAIR("Post Move with Axis ", axis, " soon.");
+    //SERIAL_ECHOLNPAIR("Post Move with Axis ", AS_CHAR(axis_codes[axis]), " soon.");
   }
 
   #if ENABLED(AUTO_BED_LEVELING_UBL)

Marlin/src/module/motion.cpp

     #endif
 
     if (DEBUGGING(LEVELING))
-      SERIAL_ECHOLNPAIR("Axis ", XYZ_CHAR(axis), " min:", soft_endstop.min[axis], " max:", soft_endstop.max[axis]);
+      SERIAL_ECHOLNPAIR("Axis ", AS_CHAR(XYZ_CHAR(axis)), " min:", soft_endstop.min[axis], " max:", soft_endstop.max[axis]);
   }
 
   /**
    * "trusted" position).
    */
   void set_axis_never_homed(const AxisEnum axis) {
-    if (DEBUGGING(LEVELING)) DEBUG_ECHOLNPAIR(">>> set_axis_never_homed(", axis_codes[axis], ")");
+    if (DEBUGGING(LEVELING)) DEBUG_ECHOLNPAIR(">>> set_axis_never_homed(", AS_CHAR(axis_codes[axis]), ")");
 
     set_axis_untrusted(axis);
     set_axis_unhomed(axis);
 
-    if (DEBUGGING(LEVELING)) DEBUG_ECHOLNPAIR("<<< set_axis_never_homed(", axis_codes[axis], ")");
+    if (DEBUGGING(LEVELING)) DEBUG_ECHOLNPAIR("<<< set_axis_never_homed(", AS_CHAR(axis_codes[axis]), ")");
 
     TERN_(I2C_POSITION_ENCODERS, I2CPEM.unhomed(axis));
   }
       if (ABS(phaseDelta) * planner.steps_to_mm[axis] / phasePerUStep < 0.05f)
         SERIAL_ECHOLNPAIR("Selected home phase ", home_phase[axis],
                          " too close to endstop trigger phase ", phaseCurrent,
-                         ". Pick a different phase for ", axis_codes[axis]);
+                         ". Pick a different phase for ", AS_CHAR(axis_codes[axis]));
 
       // Skip to next if target position is behind current. So it only moves away from endstop.
       if (phaseDelta < 0) phaseDelta += 1024;
       // Optional debug messages
       if (DEBUGGING(LEVELING)) {
         DEBUG_ECHOLNPAIR(
-          "Endstop ", axis_codes[axis], " hit at Phase:", phaseCurrent,
+          "Endstop ", AS_CHAR(axis_codes[axis]), " hit at Phase:", phaseCurrent,
           " Delta:", phaseDelta, " Distance:", mmDelta
         );
       }
       if (!_CAN_HOME(X) && !_CAN_HOME(Y) && !_CAN_HOME(Z)) return;
     #endif
 
-    if (DEBUGGING(LEVELING)) DEBUG_ECHOLNPAIR(">>> homeaxis(", axis_codes[axis], ")");
+    if (DEBUGGING(LEVELING)) DEBUG_ECHOLNPAIR(">>> homeaxis(", AS_CHAR(axis_codes[axis]), ")");
 
     const int axis_home_dir = TERN0(DUAL_X_CARRIAGE, axis == X_AXIS)
                 ? x_home_dir(active_extruder) : home_dir(axis);
           case Z_AXIS: es = Z_ENDSTOP; break;
         }
         if (TEST(endstops.state(), es)) {
-          SERIAL_ECHO_MSG("Bad ", axis_codes[axis], " Endstop?");
+          SERIAL_ECHO_MSG("Bad ", AS_CHAR(axis_codes[axis]), " Endstop?");
           kill(GET_TEXT(MSG_KILL_HOMING_FAILED));
         }
       #endif
       if (axis == Z_AXIS) fwretract.current_hop = 0.0;
     #endif
 
-    if (DEBUGGING(LEVELING)) DEBUG_ECHOLNPAIR("<<< homeaxis(", axis_codes[axis], ")");
+    if (DEBUGGING(LEVELING)) DEBUG_ECHOLNPAIR("<<< homeaxis(", AS_CHAR(axis_codes[axis]), ")");
 
   } // homeaxis()
 
       DEBUG_ECHOLNPAIR("> home_offset[", AS_CHAR(axis_codes[axis]), "] = ", home_offset[axis]);
     #endif
     DEBUG_POS("", current_position);
-    DEBUG_ECHOLNPAIR("<<< set_axis_is_at_home(", axis_codes[axis], ")");
+    DEBUG_ECHOLNPAIR("<<< set_axis_is_at_home(", AS_CHAR(axis_codes[axis]), ")");
   }
 }
 
 #if HAS_WORKSPACE_OFFSET
   void update_workspace_offset(const AxisEnum axis) {
     workspace_offset[axis] = home_offset[axis] + position_shift[axis];
-    if (DEBUGGING(LEVELING)) DEBUG_ECHOLNPAIR("Axis ", XYZ_CHAR(axis), " home_offset = ", home_offset[axis], " position_shift = ", position_shift[axis]);
+    if (DEBUGGING(LEVELING)) DEBUG_ECHOLNPAIR("Axis ", AS_CHAR(XYZ_CHAR(axis)), " home_offset = ", home_offset[axis], " position_shift = ", position_shift[axis]);
   }
 #endif