atmel-samd: Pin reset improvements.

* Reset SWD lines to SWD rather than GPIO. This makes OpenOCD happier.
* Default speaker enable lines to False for CircuitPlayground to prevent
  the speaker from buzzing when no sound is playing. Fixes #126

atmel-samd/boards/circuitplayground_express/mpconfigboard.h

@@ -30,6 +30,8 @@
 #define MICROPY_PORT_A        (PORT_PA16 | PORT_PA20 | PORT_PA21 | PORT_PA24 | PORT_PA25)
 #define MICROPY_PORT_B        (PORT_PB22)
 
+#define SPEAKER_ENABLE_PIN    (&pin_PA30)
+
 #define AUTORESET_DELAY_MS 500
 
 #include "spi_flash.h"

atmel-samd/common-hal/microcontroller/Pin.c

@@ -26,6 +26,8 @@
 
 #include "shared-bindings/microcontroller/Pin.h"
 
+#include "asf/sam0/drivers/port/port.h"
+
 #include "rgb_led_status.h"
 #include "samd21_pins.h"
 
@@ -36,6 +38,47 @@ bool neopixel_in_use;
 bool apa102_sck_in_use;
 bool apa102_mosi_in_use;
 #endif
+#ifdef SPEAKER_ENABLE_PIN
+bool speaker_enable_in_use;
+#endif
+
+void reset_all_pins(void) {
+    struct system_pinmux_config config;
+    system_pinmux_get_config_defaults(&config);
+    config.powersave = true;
+
+    uint32_t pin_mask[2] = PORT_OUT_IMPLEMENTED;
+
+    // Do not full reset USB or SWD lines.
+    pin_mask[0] &= ~(PIN_PA24 | PIN_PA25 | PIN_PA30 | PIN_PA31);
+
+    system_pinmux_group_set_config(&(PORT->Group[0]), pin_mask[0] & ~MICROPY_PORT_A, &config);
+    system_pinmux_group_set_config(&(PORT->Group[1]), pin_mask[1] & ~MICROPY_PORT_B, &config);
+
+    // Configure SWD
+    system_pinmux_get_config_defaults(&config);
+    config.mux_position = 0x6;
+    system_pinmux_group_set_config(&(PORT->Group[0]), PIN_PA30 | PIN_PA31, &config);
+
+    #ifdef MICROPY_HW_NEOPIXEL
+    neopixel_in_use = false;
+    #endif
+    #ifdef MICROPY_HW_APA102_MOSI
+    apa102_sck_in_use = false;
+    apa102_mosi_in_use = false;
+    #endif
+
+    // After configuring SWD because it may be shared.
+    #ifdef SPEAKER_ENABLE_PIN
+    speaker_enable_in_use = false;
+    struct port_config pin_conf;
+    port_get_config_defaults(&pin_conf);
+
+    pin_conf.direction  = PORT_PIN_DIR_OUTPUT;
+    port_pin_set_config(SPEAKER_ENABLE_PIN->pin, &pin_conf);
+    port_pin_set_output_level(SPEAKER_ENABLE_PIN->pin, false);
+    #endif
+}
 
 void reset_pin(uint8_t pin) {
     if (pin >= PORT_BITS) {
@@ -63,8 +106,24 @@ void reset_pin(uint8_t pin) {
 
     struct system_pinmux_config config;
     system_pinmux_get_config_defaults(&config);
+    if (pin == PIN_PA30 || pin == PIN_PA31) {
+        config.mux_position = 0x6;
+    } else {
         config.powersave = true;
+    }
     system_pinmux_pin_set_config(pin, &config);
+
+    #ifdef SPEAKER_ENABLE_PIN
+    if (pin == SPEAKER_ENABLE_PIN->pin) {
+        speaker_enable_in_use = false;
+        struct port_config pin_conf;
+        port_get_config_defaults(&pin_conf);
+
+        pin_conf.direction  = PORT_PIN_DIR_OUTPUT;
+        port_pin_set_config(SPEAKER_ENABLE_PIN->pin, &pin_conf);
+        port_pin_set_output_level(SPEAKER_ENABLE_PIN->pin, false);
+    }
+    #endif
 }
 
 void claim_pin(const mcu_pin_obj_t* pin) {
@@ -81,6 +140,12 @@ void claim_pin(const mcu_pin_obj_t* pin) {
         apa102_sck_in_use = true;
     }
     #endif
+
+    #ifdef SPEAKER_ENABLE_PIN
+    if (pin == SPEAKER_ENABLE_PIN) {
+        speaker_enable_in_use = true;
+    }
+    #endif
 }
 
 bool common_hal_mcu_pin_is_free(const mcu_pin_obj_t* pin) {
@@ -98,10 +163,21 @@ bool common_hal_mcu_pin_is_free(const mcu_pin_obj_t* pin) {
     }
     #endif
 
+    #ifdef SPEAKER_ENABLE_PIN
+    if (pin == SPEAKER_ENABLE_PIN) {
+        return !speaker_enable_in_use;
+    }
+    #endif
+
     PortGroup *const port = system_pinmux_get_group_from_gpio_pin(pin->pin);
     uint32_t pin_index = (pin->pin);
-    PORT_PINCFG_Type state = port->PINCFG[pin_index];
+    volatile PORT_PINCFG_Type *state = &port->PINCFG[pin_index];
+    volatile PORT_PMUX_Type *pmux = &port->PMUX[pin_index / 2];
 
-    return state.bit.PMUXEN == 0 && state.bit.INEN == 0 &&
+    if (pin->pin == PIN_PA30 || pin->pin == PIN_PA31) {
-           state.bit.PULLEN == 0 && (port->DIR.reg & (1 << pin_index)) == 0;
+        return state->bit.PMUXEN == 1 && ((pmux->reg >> (4 * pin_index % 2)) & 0xf) == 0x6;
+    }
+
+    return state->bit.PMUXEN == 0 && state->bit.INEN == 0 &&
+           state->bit.PULLEN == 0 && (port->DIR.reg & (1 << pin_index)) == 0;
 }

atmel-samd/common-hal/microcontroller/Pin.h

@@ -78,6 +78,7 @@ extern bool apa102_sck_in_use;
 extern bool apa102_mosi_in_use;
 #endif
 
+void reset_all_pins(void);
 // reset_pin takes the pin number instead of the pointer so that objects don't
 // need to store a full pointer.
 void reset_pin(uint8_t pin);

atmel-samd/main.c

@@ -172,15 +172,7 @@ void reset_samd21(void) {
     while (DAC->STATUS.reg & DAC_STATUS_SYNCBUSY) {}
     DAC->CTRLA.reg |= DAC_CTRLA_SWRST;
 
-    // Reset pins
+    reset_all_pins();
-    struct system_pinmux_config config;
-    system_pinmux_get_config_defaults(&config);
-    config.powersave = true;
-
-    uint32_t pin_mask[2] = PORT_OUT_IMPLEMENTED;
-
-    system_pinmux_group_set_config(&(PORT->Group[0]), pin_mask[0] & ~MICROPY_PORT_A, &config);
-    system_pinmux_group_set_config(&(PORT->Group[1]), pin_mask[1] & ~MICROPY_PORT_B, &config);
 
     audioout_reset();
     pwmout_reset();