diff --git a/include/libopencm3/stm32/common/dac_common_all.h b/include/libopencm3/stm32/common/dac_common_all.h
index c93b9dbc..069d6a65 100644
--- a/include/libopencm3/stm32/common/dac_common_all.h
+++ b/include/libopencm3/stm32/common/dac_common_all.h
@@ -100,7 +100,7 @@ specific memorymap.h header before including this header file.*/
 /** DMAEN2: DAC channel2 DMA enable */
 #define DAC_CR_DMAEN2			(1 << 28)
 
-/** MAMP2[3:0]: DAC channel2 mask/amplitude selector */
+/** MAMP2[3:0]: DAC channel2 mask/amplitude selector field position */
 #define DAC_CR_MAMP2_SHIFT		24
 
 /** WAVE2[1:0]: DAC channel2 noise/triangle wave generation enable */
@@ -118,8 +118,10 @@ specific memorymap.h header before including this header file.*/
 /** DMAEN1: DAC channel1 DMA enable */
 #define DAC_CR_DMAEN1			(1 << 12)
 
-/** MAMP1[3:0]: DAC channel1 mask/amplitude selector */
+/** MAMP1[3:0]: DAC channel1 mask/amplitude selector field position */
 #define DAC_CR_MAMP1_SHIFT		8
+/** MAMP Mask/Amplitude selector field size */
+#define DAC_CR_MAMPx_MASK		0xf
 
 /** WAVEn[1:0]: DAC channel1 noise/triangle wave generation enable */
 #define DAC_CR_WAVE1_SHIFT		6
@@ -257,7 +259,7 @@ void dac_trigger_disable(uint32_t dac, int channel);
 void dac_set_trigger_source(uint32_t dac, uint32_t source);
 void dac_set_waveform_generation(uint32_t dac, enum dac_wave wave);
 void dac_disable_waveform_generation(uint32_t dac, int channel);
-void dac_set_waveform_characteristics(uint32_t dac, uint8_t mamp);
+void dac_set_waveform_characteristics(uint32_t dac, int channel, int mamp);
 void dac_load_data_buffer_single(uint32_t dac, uint16_t data,
                                  enum dac_align align, int channel);
 void dac_load_data_buffer_dual(uint32_t dac, uint16_t data1, uint16_t data2,
diff --git a/lib/stm32/common/dac_common_all.c b/lib/stm32/common/dac_common_all.c
index bc26ef74..6b88d10a 100644
--- a/lib/stm32/common/dac_common_all.c
+++ b/lib/stm32/common/dac_common_all.c
@@ -347,12 +347,31 @@ become read-only.
 @note The DAC trigger must be enabled for this to work.
 
 @param[in] dac the base address of the DAC. @ref dac_reg_base
-@param[in] mamp uint8_t. Taken from @ref dac_mamp2 or @ref dac_mamp1 or a
-logical OR of one of each of these to set both channels simultaneously.
+@param[in] channel one or both, select from @ref dac_channel_id
+@param[in] mamp amplitude of mixed waveform, bit width @ref DAC_CR_MAMPx_MASK
 */
-void dac_set_waveform_characteristics(uint32_t dac, uint8_t mamp)
+void dac_set_waveform_characteristics(uint32_t dac, int channel, int mamp)
 {
-	DAC_CR(dac) |= mamp;
+	uint32_t reg = DAC_CR(dac);
+	switch(channel) {
+	case DAC_CHANNEL1:
+		reg &= ~(DAC_CR_MAMPx_MASK << DAC_CR_MAMP1_SHIFT);
+		reg |= mamp << DAC_CR_MAMP1_SHIFT;
+		break;
+	case DAC_CHANNEL2:
+		reg &= ~(DAC_CR_MAMPx_MASK << DAC_CR_MAMP2_SHIFT);
+		reg |= mamp << DAC_CR_MAMP2_SHIFT;
+		break;
+	case DAC_CHANNEL_BOTH:
+		reg &= ~(DAC_CR_MAMPx_MASK << DAC_CR_MAMP1_SHIFT)
+			| ~(DAC_CR_MAMPx_MASK << DAC_CR_MAMP2_SHIFT);
+		reg |= mamp << DAC_CR_MAMP1_SHIFT;
+		reg |= mamp << DAC_CR_MAMP2_SHIFT;
+		break;
+	default:
+		break;
+	}
+	DAC_CR(dac) = reg;
 }
 
 /** @brief Load DAC Data Register.