Reduce memory use

* Command definition now uses char * instead of String
 * registered_commands is now an array of pointers to Commands,
   previously this was an array of Command and was allocated to
   MAX_COMMANDS entries which were then overwritten with the module
   provided Commands, so every Command used twice as much memory. This
   saves ~200bytes
 * Several (u)ints are now (u)int8_t

On the nano with all modules included this reduces global RAM use from
1676 bytes to 1237 bytes (from 81.8% to 60.4%).

src/main.cpp

@@ -36,10 +36,10 @@
 #include "modules/light_sensor/light_sensor.h"
 #endif
 
-Command registered_commands[MAX_COMMANDS];
+const Command * registered_commands[MAX_COMMANDS];
 void (*registered_loop_functions[MAX_MODULES])(void);
 
-uint16_t registered_commands_count = 0;
+uint8_t registered_commands_count = 0;
 uint8_t registered_loop_fn_count = 0;
 
 const Command core_commands[] = {
@@ -50,7 +50,7 @@ const Command core_commands[] = {
 void register_module(const Command commands[], void (*loop_fn)(void))
 {
     for (int i = 0; CHECK_END_COMMAND(commands[i]); i++)
-        registered_commands[registered_commands_count++] = commands[i];
+        registered_commands[registered_commands_count++] = &commands[i];
 
     if (loop_fn)
         registered_loop_functions[registered_loop_fn_count++] = loop_fn;
@@ -58,10 +58,10 @@ void register_module(const Command commands[], void (*loop_fn)(void))
 
 void handle_command(String received_command)
 {
-    for (int i = 0; CHECK_END_COMMAND(registered_commands[i]); i++)
+    for (int i = 0; CHECK_END_COMMAND(*registered_commands[i]); i++)
     {
-        if (received_command.startsWith(registered_commands[i].command))
-            return registered_commands[i].run(received_command.substring(registered_commands[i].command.length()));
+        if (received_command.startsWith(registered_commands[i]->command))
+            return registered_commands[i]->run(received_command.substring(strlen(registered_commands[i]->command)));
     }
 
 #ifdef HELP
@@ -151,7 +151,7 @@ void setup()
     endstops_setup();
 #endif
 
-    registered_commands[registered_commands_count] = END_COMMAND;
+    registered_commands[registered_commands_count] = &end_command;
     Serial.println(F(VERSION_STRING));
 }
 

src/main.h

@@ -11,14 +11,18 @@
     {               \
         "", NULL    \
     }
-#define CHECK_END_COMMAND(C) C.command.length() > 0
+#define CHECK_END_COMMAND(C) check_end_command(C)
 
 struct Command
 {
-    String command;
+    const char * command;
     void (*run)(String);
 };
 
+inline bool check_end_command(Command c) { return strlen(c.command) > 0; }
+inline bool check_end_command(Command * c) {return strlen(c->command) > 0; }
+
+const Command end_command = END_COMMAND;
 uint8_t parse_arguments(char ** arguments, String, uint8_t);
 extern void register_module(const Command commands[], void (*loop_fn)(void));
 

src/modules/endstops/endstops.cpp

@@ -11,12 +11,12 @@
 unsigned long retreat_steps = 5000;
 unsigned long home_move_steps = 100000;
 unsigned long axis_max[STAGE_N_MOTORS];
-const int axis_max_eeprom = sizeof(long)*(STAGE_N_MOTORS+2);
+const uint8_t axis_max_eeprom = sizeof(long)*(STAGE_N_MOTORS+2);
 #ifdef ENDSTOPS_MIN
-const int endstops_min_pins[] = WIRING_ENDSTOPS_MIN;
+const uint8_t endstops_min_pins[] = WIRING_ENDSTOPS_MIN;
 #endif
 #ifdef ENDSTOPS_MAX
-const int endstops_max_pins[] = WIRING_ENDSTOPS_MAX;
+const uint8_t endstops_max_pins[] = WIRING_ENDSTOPS_MAX;
 #endif
 bool endstops_enabled = true;
 

src/modules/stage/stage.cpp

@@ -10,13 +10,13 @@
 #include "main.h"
 
 // The array below has 3 stepper objects, for X,Y,Z respectively
-const int n_motors = 3;
+const uint8_t n_motors = 3;
 long min_step_delay;
-const int min_step_delay_eeprom = sizeof(long) * n_motors;
+const uint8_t min_step_delay_eeprom = sizeof(long) * n_motors;
 long ramp_time;
-const int ramp_time_eeprom = sizeof(long) * (n_motors + 1);
-const int axis_max_eeprom = sizeof(long) * (n_motors + 2);
-const int non_blocking_moves_eeprom = sizeof(long) * (n_motors + 3);
+const uint8_t ramp_time_eeprom = sizeof(long) * (n_motors + 1);
+const uint8_t axis_max_eeprom = sizeof(long) * (n_motors + 2);
+const uint8_t non_blocking_moves_eeprom = sizeof(long) * (n_motors + 3);
 Stepper *motors[n_motors];
 signed long current_pos[n_motors];
 long steps_remaining[n_motors];
@@ -93,7 +93,7 @@ void start_move(long displ[n_motors])
 {
     // move all the axes in a nice move
     // split displacements into magnitude and direction, and find max. travel
-    unsigned long max_steps = 0;
+    long max_steps = 0;
     EACH_MOTOR
     {
         move_directions[i] = displ[i] > 0 ? 1 : -1;
@@ -103,7 +103,9 @@ void start_move(long displ[n_motors])
     }
     // scale the step delays so the move goes in a straight line, with >=1 motor
     // running at max. speed.
-    EACH_MOTOR {if (displacement[i] > 0)
+    EACH_MOTOR
+    {
+        if (displacement[i] > 0)
         {
             step_delay[i] = float(max_steps) / float(displacement[i]) * float(min_step_delay);
         }