Make KeyMatrix row output switch faster

dhalbert · dhalbert · commit f1d2eee58f16 · 2021-07-21T09:08:32.000-04:00
diff --git a/shared-module/keypad/KeyMatrix.c b/shared-module/keypad/KeyMatrix.c
@@ -153,8 +153,9 @@ void keypad_keymatrix_scan(keypad_keymatrix_obj_t *self) {
     for (size_t row = 0; row < common_hal_keypad_keymatrix_get_row_count(self); row++) {
         // Switch this row to an output and set level appropriately
         // Set low if columns_to_anodes is true, else set high.
+        digitalio_digitalinout_obj_t *row_dio = self->row_digitalinouts->items[row];
         common_hal_digitalio_digitalinout_switch_to_output(
-            self->row_digitalinouts->items[row], !self->columns_to_anodes, DRIVE_MODE_PUSH_PULL);
+            row_dio, !self->columns_to_anodes, DRIVE_MODE_PUSH_PULL);
 
         for (size_t column = 0; column < common_hal_keypad_keymatrix_get_column_count(self); column++) {
             mp_uint_t key_number = row_column_to_key_number(self, row, column);
@@ -175,8 +176,12 @@ void keypad_keymatrix_scan(keypad_keymatrix_obj_t *self) {
             }
         }
 
+        // Done with this row. Set its pin to its resting pull value briefly to shorten the time it takes
+        // to switch values. Just switching to an input with a (relatively weak) pullup/pulldown
+        // causes a slight delay in the output changing, which can cause false readings.
+        common_hal_digitalio_digitalinout_set_value(row_dio, self->columns_to_anodes);
         // Switch the row back to an input, pulled appropriately
         common_hal_digitalio_digitalinout_switch_to_input(
-            self->row_digitalinouts->items[row], self->columns_to_anodes ? PULL_UP : PULL_DOWN);
+            row_dio, self->columns_to_anodes ? PULL_UP : PULL_DOWN);
     }
 }

Original file line number	Diff line number	Diff line change
`@@ -153,8 +153,9 @@ void keypad_keymatrix_scan(keypad_keymatrix_obj_t *self) {`
`153`	`153`	`for (size_t row = 0; row < common_hal_keypad_keymatrix_get_row_count(self); row++) {`
`154`	`154`	`// Switch this row to an output and set level appropriately`
`155`	`155`	`// Set low if columns_to_anodes is true, else set high.`
	`156`	`+ digitalio_digitalinout_obj_t *row_dio = self->row_digitalinouts->items[row];`
`156`	`157`	`common_hal_digitalio_digitalinout_switch_to_output(`
`157`		`- self->row_digitalinouts->items[row], !self->columns_to_anodes, DRIVE_MODE_PUSH_PULL);`
	`158`	`+ row_dio, !self->columns_to_anodes, DRIVE_MODE_PUSH_PULL);`
`158`	`159`
`159`	`160`	`for (size_t column = 0; column < common_hal_keypad_keymatrix_get_column_count(self); column++) {`
`160`	`161`	`mp_uint_t key_number = row_column_to_key_number(self, row, column);`
`@@ -175,8 +176,12 @@ void keypad_keymatrix_scan(keypad_keymatrix_obj_t *self) {`
`175`	`176`	`}`
`176`	`177`	`}`
`177`	`178`
	`179`	`+ // Done with this row. Set its pin to its resting pull value briefly to shorten the time it takes`
	`180`	`+ // to switch values. Just switching to an input with a (relatively weak) pullup/pulldown`
	`181`	`+ // causes a slight delay in the output changing, which can cause false readings.`
	`182`	`+ common_hal_digitalio_digitalinout_set_value(row_dio, self->columns_to_anodes);`
`178`	`183`	`// Switch the row back to an input, pulled appropriately`
`179`	`184`	`common_hal_digitalio_digitalinout_switch_to_input(`
`180`		`- self->row_digitalinouts->items[row], self->columns_to_anodes ? PULL_UP : PULL_DOWN);`
	`185`	`+ row_dio, self->columns_to_anodes ? PULL_UP : PULL_DOWN);`
`181`	`186`	`}`
`182`	`187`	`}`