Experimental: send interrupt to host on control change.

Currently crashes if volume is changed via encoder and then adjusted from the system.
pimoroni · Mar 12, 2024 · 84c127f · 84c127f
1 parent 492de18
commit 84c127f
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diff --git a/src/main.c b/src/main.c
@@ -151,6 +151,12 @@ int main(void)
 // Device callbacks
 //--------------------------------------------------------------------+
 
+bool tud_audio_int_ctr_done_cb(uint8_t rhport, uint16_t n_bytes_copied)
+{
+  system_led(128, 128, 0);
+  return true;
+}
+
 // Invoked when device is mounted
 void tud_mount_cb(void)
 {
@@ -425,6 +431,54 @@ bool tud_audio_tx_done_pre_load_cb(uint8_t rhport, uint8_t itf, uint8_t ep_in, u
 // AUDIO Task
 //--------------------------------------------------------------------+
 
+#define STATUS_INTERRUPT_INFO_ORIGIN_INTERFACE 0x00
+#define STATUS_INTERRUPT_CONTROL_MASTER 0x00
+
+// Cribbed from https://github.com/hathach/tinyusb/pull/1702
+// UAC2 §6.1 "interrupt data message"
+typedef struct TU_ATTR_PACKED
+{
+  uint8_t bInfo;
+  uint8_t bAttribute;
+  union TU_ATTR_PACKED
+  {
+    uint16_t wValue;
+    struct TU_ATTR_PACKED
+    {
+      uint8_t wValue_cn_or_mcn;
+      uint8_t wValue_cs;
+    };
+  };
+  union TU_ATTR_PACKED
+  {
+    uint16_t wIndex;
+    struct TU_ATTR_PACKED
+    {
+      uint8_t wIndex_ep_or_int;
+      uint8_t wIndex_entity_id;
+    };
+  };
+} audio_status_update_t;
+
+static const audio_status_update_t status_message_queue[2] = {
+	{
+		.bInfo = STATUS_INTERRUPT_INFO_ORIGIN_INTERFACE,
+		.bAttribute = AUDIO_CS_REQ_CUR,
+		.wValue_cn_or_mcn = STATUS_INTERRUPT_CONTROL_MASTER,
+		.wValue_cs = AUDIO_FU_CTRL_VOLUME,
+		.wIndex_ep_or_int = ITF_NUM_AUDIO_CONTROL,
+		.wIndex_entity_id = UAC2_ENTITY_SPK_INPUT_TERMINAL,
+	},
+	{
+		.bInfo = STATUS_INTERRUPT_INFO_ORIGIN_INTERFACE,
+		.bAttribute = AUDIO_CS_REQ_CUR,
+		.wValue_cn_or_mcn = STATUS_INTERRUPT_CONTROL_MASTER,
+		.wValue_cs = AUDIO_FU_CTRL_MUTE,
+		.wIndex_ep_or_int = ITF_NUM_AUDIO_CONTROL,
+		.wIndex_entity_id = UAC2_ENTITY_SPK_INPUT_TERMINAL,
+	},
+};
+
 void audio_task(void)
 {
   static uint32_t start_ms = 0;
@@ -456,6 +510,9 @@ void audio_task(void)
 
       volume[0] = system_volume * 100;
       volume[1] = system_volume * 100;
+
+      const uint8_t *buf = (const uint8_t *)&status_message_queue[0];
+      tud_audio_int_ctr_n_write(0, buf, 6);
     }
 
     start_ms += volume_interval_ms;

diff --git a/src/tusb_config.h b/src/tusb_config.h
@@ -93,6 +93,8 @@ extern "C" {
 #define CFG_TUD_ENDPOINT0_SIZE    64
 #endif
 
+#define CFG_TUD_AUDIO_INT_CTR_EPSIZE_IN 6
+
 //------------- CLASS -------------//
 #define CFG_TUD_CDC               0
 #define CFG_TUD_MSC               0

diff --git a/src/usb_descriptors.h b/src/usb_descriptors.h
@@ -42,7 +42,17 @@ enum
   ITF_NUM_TOTAL
 };
 
+#define TUD_AUDIO_DESC_AC_INT_LEN 7 
+#define TUD_AUDIO_DESC_AC_INT(ep) \
+  TUD_AUDIO_DESC_AC_INT_LEN /* Bytes */, \
+  TUSB_DESC_ENDPOINT, \
+	ep /* Endpoint */, \
+	TUSB_XFER_INTERRUPT /* Interrupt type */, \
+	U16_TO_U8S_LE(6) /* Buffer size as per standard */, \
+	10
+
 #define TUD_AUDIO_HEADSET_STEREO_DESC_LEN (TUD_AUDIO_DESC_IAD_LEN\
+    + TUD_AUDIO_DESC_AC_INT_LEN\
     + TUD_AUDIO_DESC_STD_AC_LEN\
     + TUD_AUDIO_DESC_CS_AC_LEN\
     + TUD_AUDIO_DESC_CLK_SRC_LEN\
@@ -81,6 +91,7 @@ enum
     /* Output Terminal Descriptor(4.7.2.5) */\
     TUD_AUDIO_DESC_OUTPUT_TERM(/*_termid*/ UAC2_ENTITY_SPK_OUTPUT_TERMINAL, /*_termtype*/ AUDIO_TERM_TYPE_OUT_GENERIC_SPEAKER, /*_assocTerm*/ 0x00, /*_srcid*/ UAC2_ENTITY_SPK_FEATURE_UNIT, /*_clkid*/ UAC2_ENTITY_CLOCK, /*_ctrl*/ 0x0000, /*_stridx*/ 0x00),\
     /* Standard AS Interface Descriptor(4.9.1) */\
+    TUD_AUDIO_DESC_AC_INT(_epin),\
     /* Interface 1, Alternate 0 - default alternate setting with 0 bandwidth */\
     TUD_AUDIO_DESC_STD_AS_INT(/*_itfnum*/ (uint8_t)(ITF_NUM_AUDIO_STREAMING_SPK), /*_altset*/ 0x00, /*_nEPs*/ 0x00, /*_stridx*/ 0x05),\
     /* Standard AS Interface Descriptor(4.9.1) */\