Turn on touchio for M0 boards. M4 will come later once its supported

by FreeTouch.

Fixes #670

ports/atmel-samd/Makefile

@@ -274,7 +274,7 @@ SRC_C = \
 	lib/libc/string0.c \
 	lib/mp-readline/readline.c \
 	$(BUILD)/autogen_usb_descriptor.c \
-	# freetouch/adafruit_ptc.c
+	freetouch/adafruit_ptc.c
 
 # Choose which flash filesystem impl to use.
 # (Right now INTERNAL_FLASH_FILESYSTEM and SPI_FLASH_FILESYSTEM are mutually exclusive.
@@ -321,7 +321,7 @@ SRC_COMMON_HAL = \
 	usb_hid/Device.c \
 	audioio/__init__.c \
 	audioio/AudioOut.c \
-#	touchio/__init__.c \
+	touchio/__init__.c \
 	touchio/TouchIn.c \
 
 ifeq ($(INTERNAL_LIBM),1)

ports/atmel-samd/common-hal/touchio/TouchIn.c

@@ -33,11 +33,18 @@
 #include "py/mphal.h"
 #include "shared-bindings/touchio/TouchIn.h"
 
+#ifdef SAMD21
+#include "hpl/pm/hpl_pm_base.h"
+#endif
+
+#include "clocks.h"
 #include "samd21_pins.h"
 #include "tick.h"
 
 #include "adafruit_ptc.h"
 
+bool touch_enabled = false;
+
 static uint16_t get_raw_reading(touchio_touchin_obj_t *self) {
     adafruit_ptc_start_conversion(PTC, &self->config);
 
@@ -58,13 +65,21 @@ void common_hal_touchio_touchin_construct(touchio_touchin_obj_t* self,
     }
     claim_pin(pin);
 
-    /* Setup and enable generic clock source for PTC module. */
-    struct system_gclk_chan_config gclk_chan_conf;
-    system_gclk_chan_get_config_defaults(&gclk_chan_conf);
-    gclk_chan_conf.source_generator = GCLK_GENERATOR_3;
-    system_gclk_chan_set_config(PTC_GCLK_ID, &gclk_chan_conf);
-    system_gclk_chan_enable(PTC_GCLK_ID);
-    system_apb_clock_set_mask(SYSTEM_CLOCK_APB_APBC, PM_APBCMASK_PTC);
+    // Turn on the PTC if its not in use. We won't turn it off until reset.
+    #ifdef SAMD21
+    if ((( Ptc *) PTC)->CTRLA.bit.ENABLE == 0) {
+        // We run the PTC at 8mhz so divide the 48mhz clock by 6.
+        uint8_t gclk = find_free_gclk(6);
+        if (gclk > GCLK_GEN_NUM) {
+            mp_raise_RuntimeError("No free GCLKs");
+        }
+        enable_clock_generator(self->gclk, CLOCK_48MHZ, 6);
+
+        /* Setup and enable generic clock source for PTC module. */
+        connect_gclk_to_peripheral(self->gclk, PTC_GCLK_ID);
+
+        _pm_enable_bus_clock(PM_BUS_APBC, PTC);
+    }
 
     adafruit_ptc_get_config_default(&self->config);
     self->config.pin = pin->pin;
@@ -80,6 +95,7 @@ void common_hal_touchio_touchin_construct(touchio_touchin_obj_t* self,
     // but for touches using fruit or other objects, the difference is much less.
 
     self->threshold = get_raw_reading(self) + 100;
+    #endif
 }
 
 bool common_hal_touchio_touchin_deinited(touchio_touchin_obj_t* self) {
@@ -91,6 +107,8 @@ void common_hal_touchio_touchin_deinit(touchio_touchin_obj_t* self) {
     if (common_hal_touchio_touchin_deinited(self)) {
         return;
     }
+    // We leave the clocks running because they may be in use by others.s
+
     reset_pin(self->config.pin);
     self->config.pin = NO_PIN;
 }

ports/atmel-samd/common-hal/touchio/TouchIn.h

@@ -38,6 +38,7 @@ typedef struct {
     mp_obj_base_t base;
     struct adafruit_ptc_config config;
     uint16_t threshold;
+    uint8_t gclk;
 } touchio_touchin_obj_t;
 
 void touchin_reset(void);

ports/atmel-samd/freetouch

@@ -1 +1 @@
-Subproject commit c3deba11eb4be397ec719cfbfba1abcaecda2c08
+Subproject commit 5d8c33e084996d48134eaf7d4b200d1a806cb9ee

ports/atmel-samd/mpconfigport.h

@@ -238,9 +238,14 @@ extern const struct _mp_obj_module_t usb_hid_module;
 #endif
 
 // Disabled for now.
-// { MP_OBJ_NEW_QSTR(MP_QSTR_touchio), (mp_obj_t)&touchio_module },
 //    { MP_OBJ_NEW_QSTR(MP_QSTR__stage), (mp_obj_t)&stage_module },
 
+#ifdef SAMD21
+#define TOUCHIO_MODULE { MP_OBJ_NEW_QSTR(MP_QSTR_touchio), (mp_obj_t)&touchio_module },
+#endif
+#ifdef SAMD51
+#define TOUCHIO_MODULE
+#endif
 
 #define MICROPY_PORT_BUILTIN_MODULES \
     { MP_OBJ_NEW_QSTR(MP_QSTR_analogio), (mp_obj_t)&analogio_module }, \
@@ -260,6 +265,7 @@ extern const struct _mp_obj_module_t usb_hid_module;
     { MP_OBJ_NEW_QSTR(MP_QSTR_math), (mp_obj_t)&math_module }, \
     { MP_OBJ_NEW_QSTR(MP_QSTR_time), (mp_obj_t)&time_module }, \
     { MP_OBJ_NEW_QSTR(MP_QSTR_usb_hid),(mp_obj_t)&usb_hid_module }, \
+    TOUCHIO_MODULE \
     EXTRA_BUILTIN_MODULES
 
 #define MICROPY_PORT_BUILTIN_DEBUG_MODULES \