need to enable both DAC channels at once

peripherals/dac.c

@@ -72,16 +72,23 @@ void dac_init(void) {
 #endif
 }
 
-void dac_enable(uint16_t channel) {
+void dac_enable(dac_channel_mask_t channelmask) {
 #if defined(_SAMD21_) || defined(_SAMD11_)
     (void) channel;
     // Chips with a single DAC don't need to enable individual channels
 #else // SAM L21 / SAM D51
     DAC->CTRLA.bit.ENABLE = 0;
     _dac_sync();
-    DAC->DACCTRL[channel].bit.ENABLE = 1;
-    DAC->DACCTRL[channel].bit.CCTRL = DAC_DACCTRL_CCTRL_CC1M_Val;
-    DAC->DACCTRL[channel].bit.REFRESH = 2;
+    if (channelmask & 1) {
+        DAC->DACCTRL[0].bit.ENABLE = 1;
+        DAC->DACCTRL[0].bit.CCTRL = DAC_DACCTRL_CCTRL_CC1M_Val;
+        DAC->DACCTRL[0].bit.REFRESH = 2;
+    }
+    if (channelmask & 2) {
+        DAC->DACCTRL[1].bit.ENABLE = 1;
+        DAC->DACCTRL[1].bit.CCTRL = DAC_DACCTRL_CCTRL_CC1M_Val;
+        DAC->DACCTRL[1].bit.REFRESH = 2;
+    }
 #endif
     DAC->CTRLA.bit.ENABLE = 1;
     _dac_sync();

peripherals/dac.h

@@ -31,6 +31,14 @@
 #include <stdint.h>
 #include <stdbool.h>
 
+// channel mask enum for dac_enable
+typedef enum {
+    DAC_CHANNEL_NONE = 0,
+    DAC_CHANNEL_0 = 1,
+    DAC_CHANNEL_1 = 2,
+    DAC_CHANNEL_BOTH = 3
+} dac_channel_mask_t;
+
 /**
  * @brief Initializes the DAC peripheral, but does not enable it.
  * @param channel The DAC channel to enable.
@@ -39,9 +47,12 @@
 void dac_init(void);
 
 /**
- * @brief Enables the given DAC channel.
+ * @brief Enables the DAC channels specified in the mask, and disables others.
+ * @param channelmask A bitmask of the channels to enable:
+ *        1 for channel 0, 2 for channel 1, 3 for both channels.
+ *        For MCUs with only one DAC channel, this parameter is ignored.
  */
-void dac_enable(uint16_t channel);
+void dac_enable(dac_channel_mask_t channelmask);
 
 /**
  * @brief Set the analog value of the DAC.