codal_port/modmicrobit: Add microbit.scale function.

See issue #102.

Signed-off-by: Damien George <damien@micropython.org>

Author: dpgeorge

src/codal_port/modmicrobit.c

@@ -126,6 +126,36 @@ STATIC mp_obj_t microbit_run_every(size_t n_args, const mp_obj_t *pos_args, mp_m
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_KW(microbit_run_every_obj, 0, microbit_run_every);
 
+STATIC mp_obj_t microbit_scale(size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
+    enum { ARG_value, ARG_from_, ARG_to };
+    static const mp_arg_t allowed_args[] = {
+        { MP_QSTR_value, MP_ARG_REQUIRED | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
+        { MP_QSTR_from_, MP_ARG_REQUIRED | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
+        { MP_QSTR_to, MP_ARG_REQUIRED | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
+    };
+
+    mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
+    mp_arg_parse_all(n_args, pos_args, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
+
+    // Extract from/to min/max arrays.
+    mp_obj_t *from_items, *to_items;
+    mp_obj_get_array_fixed_n(args[ARG_from_].u_obj, 2, &from_items);
+    mp_obj_get_array_fixed_n(args[ARG_to].u_obj, 2, &to_items);
+
+    // Extract all float values.
+    mp_float_t from_value = mp_obj_get_float(args[ARG_value].u_obj);
+    mp_float_t from_min = mp_obj_get_float(from_items[0]);
+    mp_float_t from_max = mp_obj_get_float(from_items[1]);
+    mp_float_t to_min = mp_obj_get_float(to_items[0]);
+    mp_float_t to_max = mp_obj_get_float(to_items[1]);
+
+    // Compute scaled value.
+    mp_float_t to_value = (from_value - from_min) / (from_max - from_min) * (to_max - to_min) + to_min;
+
+    return mp_obj_new_float(to_value);
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_KW(microbit_scale_obj, 0, microbit_scale);
+
 STATIC const mp_rom_map_elem_t microbit_module_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR_microbit) },
 
@@ -155,6 +185,7 @@ STATIC const mp_rom_map_elem_t microbit_module_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR_ws2812_write), MP_ROM_PTR(&microbit_ws2812_write_obj) },
 
     { MP_ROM_QSTR(MP_QSTR_run_every), MP_ROM_PTR(&microbit_run_every_obj) },
+    { MP_ROM_QSTR(MP_QSTR_scale), MP_ROM_PTR(&microbit_scale_obj) },
 
     { MP_ROM_QSTR(MP_QSTR_pin0), MP_ROM_PTR(&microbit_p0_obj) },
     { MP_ROM_QSTR(MP_QSTR_pin1), MP_ROM_PTR(&microbit_p1_obj) },