AnalogOut / AudioOut: Copy settings from Arduino

Make changes in asf4_conf even though I think in these cases the
"peripherals" submodule is running the show.

Arduino clocks the DAC at 12MHz but uses the CCTRL setting for
clocking < 1.2MHz (100kSPS).

A fresh clock (6) is allocated for the new 12MHz clock.  This matches
the Arduino value, though not the GCLK index.

Modify other settings to more closely resemble Arduino.

In AudioOut, actually clock the waveform data from the timer we set up
for this purpose.

This gives good waveforms when setting AnalogOut full-scale in a loop,
but the rise/fall of waveforms that come from AudioOut are still erratic.
Weirdly, if AudioOut limits its range even slightly (e.g., to 1000..64000)
then the erratic

Note that this will require adafruit/samd-peripherals#26
to be accepted for the submodule update here to work.

ports/atmel-samd/asf4_conf/samd51/hpl_dac_config.h

@@ -51,7 +51,7 @@
 // <i> This defines the current in output buffer according to conversion rate
 // <id> dac0_arch_cctrl
 #ifndef CONF_DAC0_CCTRL
-#define CONF_DAC0_CCTRL 1
+#define CONF_DAC0_CCTRL 0
 #endif
 
 // <q> Run in standby
@@ -90,7 +90,7 @@
 // <i> This defines the current in output buffer according to conversion rate
 // <id> dac1_arch_cctrl
 #ifndef CONF_DAC1_CCTRL
-#define CONF_DAC1_CCTRL 1
+#define CONF_DAC1_CCTRL 0
 #endif
 
 // <q> Run in standby

ports/atmel-samd/asf4_conf/samd51/hpl_gclk_config.h

@@ -1,8 +1,9 @@
 // Circuit Python SAMD51 clock tree:
-// DFLL48M (with USBCRM on to sync with external USB ref) -> GCLK1, GCLK5
+// DFLL48M (with USBCRM on to sync with external USB ref) -> GCLK1, GCLK5, GCLK6
 //   GCLK1 (48MHz) -> 48 MHz peripherals
-//   GCLK5 (48 MHz divided down to 2 MHz) -> DPLL0, DAC peripherals
+//   GCLK5 (48 MHz divided down to 2 MHz) -> DPLL0
 //     DPLL0 (multiplied up to 120 MHz) -> GCLK0, GCLK4 (output for monitoring)
+//   GCLK6 (48 MHz divided down to 12 MHz) -> DAC
 
 // We'd like to use XOSC32K as a ref for DFLL48M on boards with a 32kHz crystal,
 // but haven't figured that out yet.
@@ -472,7 +473,7 @@
 // <i> Indicates whether generic clock 6 configuration is enabled or not
 // <id> enable_gclk_gen_6
 #ifndef CONF_GCLK_GENERATOR_6_CONFIG
-#define CONF_GCLK_GENERATOR_6_CONFIG 0
+#define CONF_GCLK_GENERATOR_6_CONFIG 1
 #endif
 
 // <h> Generic Clock Generator Control
@@ -488,7 +489,7 @@
 // <i> This defines the clock source for generic clock generator 6
 // <id> gclk_gen_6_oscillator
 #ifndef CONF_GCLK_GEN_6_SOURCE
-#define CONF_GCLK_GEN_6_SOURCE GCLK_GENCTRL_SRC_XOSC1
+#define CONF_GCLK_GEN_6_SOURCE GCLK_GENCTRL_SRC_DFLL
 #endif
 
 // <q> Run in Standby
@@ -523,22 +524,22 @@
 // <i> Indicates whether Improve Duty Cycle is enabled or not
 // <id> gclk_arch_gen_6_idc
 #ifndef CONF_GCLK_GEN_6_IDC
-#define CONF_GCLK_GEN_6_IDC 0
+#define CONF_GCLK_GEN_6_IDC 1
 #endif
 
 // <q> Generic Clock Generator Enable
 // <i> Indicates whether Generic Clock Generator Enable is enabled or not
 // <id> gclk_arch_gen_6_enable
 #ifndef CONF_GCLK_GEN_6_GENEN
-#define CONF_GCLK_GEN_6_GENEN 0
+#define CONF_GCLK_GEN_6_GENEN 1
 #endif
 // </h>
 
 //<h> Generic Clock Generator Division
 //<o> Generic clock generator 6 division <0x0000-0xFFFF>
 // <id> gclk_gen_6_div
 #ifndef CONF_GCLK_GEN_6_DIV
-#define CONF_GCLK_GEN_6_DIV 1
+#define CONF_GCLK_GEN_6_DIV 4
 #endif
 // </h>
 // </e>

ports/atmel-samd/asf4_conf/samd51/peripheral_clk_config.h

@@ -73,7 +73,7 @@
 // <id> dac_gclk_selection
 // <i> Select the clock source for DAC.
 #ifndef CONF_GCLK_DAC_SRC
-#define CONF_GCLK_DAC_SRC GCLK_PCHCTRL_GEN_GCLK5_Val
+#define CONF_GCLK_DAC_SRC GCLK_PCHCTRL_GEN_GCLK6_Val
 #endif
 
 /**

ports/atmel-samd/common-hal/audioio/AudioOut.c

@@ -198,7 +198,7 @@ void common_hal_audioio_audioout_construct(audioio_audioout_obj_t* self,
         #endif
         #ifdef SAMD51
         DAC->EVCTRL.reg |= DAC_EVCTRL_STARTEI0;
-        DAC->DACCTRL[0].reg = DAC_DACCTRL_CCTRL_CC1M |
+        DAC->DACCTRL[0].reg = DAC_DACCTRL_CCTRL_CC100K |
                               DAC_DACCTRL_ENABLE |
                               DAC_DACCTRL_LEFTADJ;
         DAC->CTRLB.reg = DAC_CTRLB_REFSEL_VREFPU;
@@ -207,7 +207,7 @@ void common_hal_audioio_audioout_construct(audioio_audioout_obj_t* self,
     #ifdef SAMD51
     if (channel1_enabled) {
         DAC->EVCTRL.reg |= DAC_EVCTRL_STARTEI1;
-        DAC->DACCTRL[1].reg = DAC_DACCTRL_CCTRL_CC1M |
+        DAC->DACCTRL[1].reg = DAC_DACCTRL_CCTRL_CC100K |
                               DAC_DACCTRL_ENABLE |
                               DAC_DACCTRL_LEFTADJ;
         DAC->CTRLB.reg = DAC_CTRLB_REFSEL_VREFPU;
@@ -385,19 +385,17 @@ void common_hal_audioio_audioout_play(audioio_audioout_obj_t* self,
 
     #ifdef SAMD51
     uint32_t left_channel_reg = (uint32_t) &DAC->DATABUF[0].reg;
-    uint8_t left_channel_trigger = DAC_DMAC_ID_EMPTY_0;
+    uint8_t tc_trig_id = TC0_DMAC_ID_OVF + 3 * self->tc_index;
+    uint8_t left_channel_trigger = tc_trig_id;
     uint32_t right_channel_reg = 0;
-    uint8_t right_channel_trigger = 0;
+    uint8_t right_channel_trigger = tc_trig_id;
     if (self->left_channel == &pin_PA05) {
         left_channel_reg = (uint32_t) &DAC->DATABUF[1].reg;
-        left_channel_trigger = DAC_DMAC_ID_EMPTY_1;
     } else if (self->right_channel == &pin_PA05) {
         right_channel_reg = (uint32_t) &DAC->DATABUF[1].reg;
-        right_channel_trigger = DAC_DMAC_ID_EMPTY_1;
     }
     if (self->right_channel == &pin_PA02) {
         right_channel_reg = (uint32_t) &DAC->DATABUF[0].reg;
-        right_channel_trigger = DAC_DMAC_ID_EMPTY_0;
     }
     result = audio_dma_setup_playback(&self->left_dma, sample, loop, true, 0,
                                       false /* output unsigned */,