sys/analog_util: add DAC sine wave generation function by fabian18 · Pull Request #22624 · RIOT-OS/RIOT

fabian18 · 2026-08-26T11:28:48Z

Contribution description

With DAC and DMA implementation, it is possible to create a controlled sine wave with frequency and amplitude.
This PR adds a dedicated function to generate the samples for a sine wave.

Testing procedure

Issues/PRs references

Depends on #22261

Declaration of AI-Tools / LLMs usage:

AI-Tools / LLMs that were used are:

ChatGPT, Gemini for review.

The `dac_set()` API says > The value is always given as 16-bit value and is internally scaled to the > actual resolution that the DAC unit provides (e.g. 12-bit). We didn't do that scaling before - enable it even though it breaks existing users.

…utput

…nce" This reverts commit 5765ebb.

crasbe

Just a quick initial look.

crasbe · 2026-08-26T11:42:50Z

+ * @param   dma[in] DMA channel to release
+ * @param   ctx[in] DMA complete callback context


Suggested change

* @param dma[in] DMA channel to release

* @param ctx[in] DMA complete callback context

* @param[in] dma DMA channel to release

* @param[in] ctx DMA complete callback context

Same for the ones below.

crasbe · 2026-08-26T11:43:14Z

@@ -1179,9 +1186,18 @@ void dma_release_channel(dma_t dma);
 * @param   dma     DMA channel reference
 * @param   trigger Trigger to use for this DMA channel
 * @param   prio    Channel priority
- * @param   irq     Whether to enable the interrupt handler for this channel
+ * @param   cb      Callback to call when DMA transfer is done, may be NULL
+ * @param   ctx     Callback context


Suggested change

* @param ctx Callback context

* @param ctx Callback context, may be NULL

crasbe · 2026-08-26T11:44:24Z

+    }
+}
+
+static void play_function(uint32_t freq, uint32_t secs, sample_gen_t fun) {


Suggested change

static void play_function(uint32_t freq, uint32_t secs, sample_gen_t fun) {

static void play_function(uint32_t freq, uint32_t secs, sample_gen_t fun)

{

@benpicco some comments belong to #22261

crasbe · 2026-08-26T11:45:30Z

+ * @retval 0                  Success
+ * @retval <0                 Negative error code on failure


Suggested change

* @retval 0 Success

* @retval <0 Negative error code on failure

* @retval 0 Success

* @retval <0 Negative error code on failure

Care to list which error codes can be returned?

crasbe · 2026-08-26T11:46:12Z

+                  uint16_t dac_ref_mv,
+                  uint16_t *buf, uint32_t *buf_max);


Suggested change

uint16_t dac_ref_mv,

uint16_t *buf, uint32_t *buf_max);

uint16_t dac_ref_mv, uint16_t *buf, uint32_t *buf_max);

crasbe · 2026-08-26T11:46:34Z

+ * @param[in] dac_ref_mv    Reference voltage of the DAC in millivolts
+ * @param[out] buf          Buffer to store the generated samples
+ * @param[in,out] buf_max   On input: maximum number of samples the buffer can hold
+ *                          On output: actual number of samples generated


I think Doxygen will render this as a single line, perhapy you have to add a dedicated line break.

Haven't checked yet.

crasbe · 2026-08-26T11:47:01Z

+                  uint16_t dac_ref_mv,
+                  uint16_t *buf, uint32_t *buf_max)


Suggested change

uint16_t dac_ref_mv,

uint16_t *buf, uint32_t *buf_max)

uint16_t dac_ref_mv, uint16_t *buf, uint32_t *buf_max)

crasbe · 2026-08-26T11:47:52Z

+/* simple function to fill buffer the size of one period */
+/* Sample period may get trimmed to align with wave period */


Suggested change

/* simple function to fill buffer the size of one period */

/* Sample period may get trimmed to align with wave period */

/* Simple function to fill buffer the size of one period.

* Sample period may get trimmed to align with wave period */

crasbe · 2026-08-26T11:49:50Z

+ *
+ * Generates Sine, Square, Triangle and Sawtooth waves using a DAC.
+ * Connect a speaker or headphones to the DAC output pins of your board,
+ * you should be able to hear the generated sounds.


Suggested change

* you should be able to hear the generated sounds.

* you should be able to hear the generated sounds.

* Remember that a microcontroller has a very limited out put drive capability,

* use an amplifier for larger speakers to avoid damagine the microcontroller!

Maybe worth adding 😇

riot-ci · 2026-08-26T14:46:58Z

Murdock results

❌ FAILED

5201115 fixup! sys/analog_util: add function to create sine wave with DAC

Success	Failures	Total	Runtime
88	0	10260	01m:13s

Artifacts

benpicco · 2026-08-27T10:03:56Z

+    uint16_t dac_max_val = dac_util_map(center_mv + amplitude_mv, 0, dac_ref_mv);
+    uint16_t dac_amplitude = dac_max_val - dac_center;
+
+#if __FPU_PRESENT


This is only set on sam0, IS_USED(MODULE_CORTEXM_FPU) will cover a few more cores

benpicco and others added 16 commits May 8, 2026 18:15

boards/same54-xpro: use analogue supply voltage as DAC reference

5765ebb

cpu/sam0_common/dma: Add functions to enable / disable DMA looping

08555f4

cpu/sam0_common/dma: add DMA callback

be4697d

drivers/periph/dac: add dac_play API for multi sample output

1d483c2

cpu/sam0_common: implement periph_dac_play

23866db

tests/periph: add test app for periph_dac_play

7c0cf01

fixup! boards/same54-xpro: use analogue supply voltage as DAC reference

23af2af

fixup! cpu/sam0_common/dma: add DMA callback

03d1857

fixup! cpu/sam0_common: implement periph_dac_play

8f9e6fb

fixup! cpu/sam0_common/dma: add DMA callback

ac1c56c

fixup! drivers/periph/dac: add dac_play API for multi sample output

a521d1f

fixup! tests/periph: add test app for periph_dac_play

d94210f

fixup! fixup! drivers/periph/dac: add dac_play API for multi sample o…

5d13ad0

…utput

Revert "boards/same54-xpro: use analogue supply voltage as DAC refere…

bcdf052

…nce" This reverts commit 5765ebb.

sys/analog_util: add function to create sine wave with DAC

54b896e

fabian18 requested review from MichelRottleuthner, MrKevinWeiss, aabadie, benpicco, dylad, keestux and leandrolanzieri as code owners August 26, 2026 11:28

github-actions Bot added Platform: ARM Platform: This PR/issue effects ARM-based platforms Area: tests Area: tests and testing framework Area: build system Area: Build system Area: drivers Area: Device drivers Area: cpu Area: CPU/MCU ports Area: sys Area: System labels Aug 26, 2026

crasbe added the Type: new feature The issue requests / The PR implemements a new feature for RIOT label Aug 26, 2026

crasbe reviewed Aug 26, 2026

View reviewed changes

benpicco reviewed Aug 27, 2026

View reviewed changes

fabian18 mentioned this pull request Sep 2, 2026

drivers/periph/dac: add dac_play API for async multi sample output #22261

Open

fabian18 added 3 commits September 2, 2026 22:40

fixup! sys/analog_util: add function to create sine wave with DAC

885bc4a

fixup! sys/analog_util: add function to create sine wave with DAC

cf3e4ec

fixup! sys/analog_util: add function to create sine wave with DAC

5201115

		* @param dma[in] DMA channel to release
		* @param ctx[in] DMA complete callback context

	* @param ctx Callback context
	* @param ctx Callback context, may be NULL

	static void play_function(uint32_t freq, uint32_t secs, sample_gen_t fun) {
	static void play_function(uint32_t freq, uint32_t secs, sample_gen_t fun)
	{

		* @retval 0 Success
		* @retval <0 Negative error code on failure

	uint16_t dac_ref_mv,
	uint16_t buf, uint32_t buf_max);
	uint16_t dac_ref_mv, uint16_t buf, uint32_t buf_max);

	uint16_t dac_ref_mv,
	uint16_t buf, uint32_t buf_max)
	uint16_t dac_ref_mv, uint16_t buf, uint32_t buf_max)

		/* simple function to fill buffer the size of one period */
		/* Sample period may get trimmed to align with wave period */

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fabian18 commented Aug 26, 2026

Contribution description

Testing procedure

Issues/PRs references

Declaration of AI-Tools / LLMs usage:

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riot-ci commented Aug 26, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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riot-ci commented Aug 26, 2026 •

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