stmhal: Add I2C.scan method, to scan all devices on the bus.

Simple way to find the address of an attached I2C device.

stmhal/i2c.c

@@ -98,14 +98,13 @@ STATIC mp_obj_t pyb_i2c_make_new(mp_obj_t type_in, uint n_args, uint n_kw, const
     return (mp_obj_t)i2c_obj;
 }
 
+// Check if an I2C device responds to the given address.
 STATIC mp_obj_t pyb_i2c_is_ready(mp_obj_t self_in, mp_obj_t i2c_addr_o) {
     pyb_i2c_obj_t *self = self_in;
     machine_uint_t i2c_addr = mp_obj_get_int(i2c_addr_o) << 1;
 
-    //printf("IsDeviceReady\n");
     for (int i = 0; i < 10; i++) {
         HAL_StatusTypeDef status = HAL_I2C_IsDeviceReady(self->i2c_handle, i2c_addr, 10, 200);
-        //printf("  got %d\n", status);
         if (status == HAL_OK) {
             return mp_const_true;
         }
@@ -116,6 +115,27 @@ STATIC mp_obj_t pyb_i2c_is_ready(mp_obj_t self_in, mp_obj_t i2c_addr_o) {
 
 STATIC MP_DEFINE_CONST_FUN_OBJ_2(pyb_i2c_is_ready_obj, pyb_i2c_is_ready);
 
+// Scan all I2C addresses from 0x01 to 0x7f and return a list of those that respond.
+STATIC mp_obj_t pyb_i2c_scan(mp_obj_t self_in) {
+    pyb_i2c_obj_t *self = self_in;
+
+    mp_obj_t list = mp_obj_new_list(0, NULL);
+
+    for (uint addr = 1; addr <= 127; addr++) {
+        for (int i = 0; i < 10; i++) {
+            HAL_StatusTypeDef status = HAL_I2C_IsDeviceReady(self->i2c_handle, addr << 1, 10, 200);
+            if (status == HAL_OK) {
+                mp_obj_list_append(list, mp_obj_new_int(addr));
+                break;
+            }
+        }
+    }
+
+    return list;
+}
+
+STATIC MP_DEFINE_CONST_FUN_OBJ_1(pyb_i2c_scan_obj, pyb_i2c_scan);
+
 STATIC mp_obj_t pyb_i2c_mem_read(uint n_args, const mp_obj_t *args) {
     pyb_i2c_obj_t *self = args[0];
     machine_uint_t i2c_addr = mp_obj_get_int(args[1]) << 1;
@@ -166,6 +186,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(pyb_i2c_mem_write_obj, 4, 4, pyb_i2c_
 
 STATIC const mp_map_elem_t pyb_i2c_locals_dict_table[] = {
     { MP_OBJ_NEW_QSTR(MP_QSTR_is_ready), (mp_obj_t)&pyb_i2c_is_ready_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_scan), (mp_obj_t)&pyb_i2c_scan_obj },
     { MP_OBJ_NEW_QSTR(MP_QSTR_mem_read), (mp_obj_t)&pyb_i2c_mem_read_obj },
     { MP_OBJ_NEW_QSTR(MP_QSTR_mem_write), (mp_obj_t)&pyb_i2c_mem_write_obj },
 };

stmhal/qstrdefsport.h

@@ -82,6 +82,7 @@ Q(MODE_EVT_RISING_FALLING)
 // for I2C object
 Q(I2C)
 Q(is_ready)
+Q(scan)
 Q(mem_read)
 Q(mem_write)