mimxrt/machine_encoder: Emulate the phases argument.

robert-hh · robert-hh · commit b6eb32caa36d · 2025-08-05T13:17:54.000+02:00
By dividing the internal counter by 1, 2 or 4. The default is 4,
matching the hardware.

Signed-off-by: robert-hh &lt;robert@hammelrath.com&gt;
diff --git a/docs/library/mimxrt.Encoder.rst b/docs/library/mimxrt.Encoder.rst
@@ -27,7 +27,7 @@ Example usage::
 Constructors
 ------------
 
-.. class:: Encoder(id, phase_a, phase_b, *, home, match_pin, filter_ns, cpc, signed, index)
+.. class:: Encoder(id, phase_a, phase_b, *, home, match_pin, filter_ns, cpc, signed, index, phases)
    :no-index:
 
     Construct and return a new quadrature encoder object using the following parameters:
@@ -72,6 +72,10 @@ Constructors
       - *index*\=value. A Pin specifier telling to which pin the index pulse is connected.
         At a rising slope of the index pulse the position counter is set to the init value
         and the cycles counter is increased by one. A *value* of *None* disables the index input.
+      - *phases* specifies the number of signal edges to count and thus the
+        granularity of the decoding. e.g. 4 phases corresponds to "4x quadrature
+        decoding", and will result in four counts per pulse. Ports may support
+        either 1, 2, or 4 phases and the default is 4 phase. *(Supported on MIMXRT)*
 
 The arguments phase_a, phase_b and filter_ns are generic across ports, all other arguments are port-specific.
 
diff --git a/ports/mimxrt/machine_encoder.c b/ports/mimxrt/machine_encoder.c
@@ -49,6 +49,7 @@ typedef struct _machine_encoder_obj_t {
     uint8_t mode;
     bool is_signed;
     uint8_t match_pin;
+    uint8_t phases;
     uint32_t cpc;
     uint32_t filter;
     uint16_t status;
@@ -403,7 +404,7 @@ static void mp_machine_encoder_init_helper_common(machine_encoder_obj_t *self,
 static void mp_machine_encoder_init_helper(machine_encoder_obj_t *self,
     size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
     enum { ARG_phase_a, ARG_phase_b, ARG_home,
-           ARG_match_pin, ARG_filter_ns, ARG_cpc, ARG_signed, ARG_index};
+           ARG_match_pin, ARG_filter_ns, ARG_cpc, ARG_signed, ARG_index, ARG_phases};
 
     static const mp_arg_t allowed_args[] = {
         { MP_QSTR_phase_a, MP_ARG_OBJ, {.u_rom_obj = mp_const_none} },
@@ -414,6 +415,7 @@ static void mp_machine_encoder_init_helper(machine_encoder_obj_t *self,
         { MP_QSTR_cpc, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = mp_const_none} },
         { MP_QSTR_signed, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = -1} },
         { MP_QSTR_index, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_INT(-1)} },
+        { MP_QSTR_phases, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 4} },
     };
     mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
     mp_arg_parse_all(n_args, pos_args, kw_args,
@@ -442,6 +444,12 @@ static void mp_machine_encoder_init_helper(machine_encoder_obj_t *self,
         }
     }
 
+    // Get the Phases argument
+    if ((args[ARG_phases].u_int != 1) && (args[ARG_phases].u_int != 2) && (args[ARG_phases].u_int != 4)) {
+        mp_raise_ValueError(MP_ERROR_TEXT("invalid value for phases"));
+    }
+    self->phases = 4 / args[ARG_phases].u_int;
+
     // Set the common options
     mp_machine_encoder_init_helper_common(self, args + ARG_match_pin, &self->enc_config);
 
@@ -552,7 +560,7 @@ static mp_obj_t machine_encoder_value(size_t n_args, const mp_obj_t *args) {
     uint32_t actual_value = ENC_GetPositionValue(self->instance);
     if (n_args > 1) {
         // Set the encoder position value and clear the rev counter.
-        uint32_t value = mp_obj_int_get_truncated(args[1]);
+        uint32_t value = mp_obj_int_get_truncated(args[1]) * (4 / self->phases);
         clear_encoder_registers(self);
         // Set the position and rev register
         ENC_SetInitialPositionValue(self->instance, value);
@@ -562,9 +570,13 @@ static mp_obj_t machine_encoder_value(size_t n_args, const mp_obj_t *args) {
     }
     // Get the position as signed or unsigned 32 bit value.
     if (self->is_signed) {
-        return mp_obj_new_int((int32_t)actual_value);
+        int32_t value = (int32_t)actual_value;
+        if (value < 0) {
+            value -= (self->phases - 1);
+        }
+        return mp_obj_new_int(value / self->phases);
     } else {
-        return mp_obj_new_int_from_uint(actual_value);
+        return mp_obj_new_int_from_uint(actual_value / self->phases);
     }
 }
 static MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(machine_encoder_value_obj, 1, 2, machine_encoder_value);
@@ -776,9 +788,36 @@ static mp_obj_t machine_counter_init(size_t n_args, const mp_obj_t *args, mp_map
 }
 MP_DEFINE_CONST_FUN_OBJ_KW(machine_counter_init_obj, 1, machine_counter_init);
 
+
+// counter.value([value])
+static mp_obj_t machine_counter_value(size_t n_args, const mp_obj_t *args) {
+    machine_encoder_obj_t *self = MP_OBJ_TO_PTR(args[0]);
+    if (!self->active) {
+        mp_raise_ValueError(MP_ERROR_TEXT("device stopped"));
+    }
+    uint32_t actual_value = ENC_GetPositionValue(self->instance);
+    if (n_args > 1) {
+        // Set the encoder position value and clear the rev counter.
+        uint32_t value = mp_obj_int_get_truncated(args[1]);
+        clear_encoder_registers(self);
+        // Set the position and rev register
+        ENC_SetInitialPositionValue(self->instance, value);
+        ENC_DoSoftwareLoadInitialPositionValue(self->instance);
+        // Reset the INIT Value
+        ENC_SetInitialPositionValue(self->instance, 0);
+    }
+    // Get the position as signed or unsigned 32 bit value.
+    if (self->is_signed) {
+        return mp_obj_new_int((int32_t)actual_value);
+    } else {
+        return mp_obj_new_int_from_uint(actual_value);
+    }
+}
+static MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(machine_counter_value_obj, 1, 2, machine_counter_value);
+
 static const mp_rom_map_elem_t machine_counter_locals_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_deinit), MP_ROM_PTR(&machine_encoder_deinit_obj) },
-    { MP_ROM_QSTR(MP_QSTR_value), MP_ROM_PTR(&machine_encoder_value_obj) },
+    { MP_ROM_QSTR(MP_QSTR_value), MP_ROM_PTR(&machine_counter_value_obj) },
     { MP_ROM_QSTR(MP_QSTR_cycles), MP_ROM_PTR(&machine_encoder_cycles_obj) },
     { MP_ROM_QSTR(MP_QSTR_init), MP_ROM_PTR(&machine_counter_init_obj) },
     { MP_ROM_QSTR(MP_QSTR_irq), MP_ROM_PTR(&machine_encoder_irq_obj) },
diff --git a/tests/extmod_hardware/machine_encoder.py b/tests/extmod_hardware/machine_encoder.py
@@ -45,7 +45,6 @@ def setUp(self):
         out0_pin(0)
         out1_pin(0)
         self.enc = Encoder(id, in0_pin, in1_pin, phases=1)
-        self.pulses = 0  # track the expected encoder position in software
         self.pulses = start_value  # track the expected encoder position in software
 
     def tearDown(self):
