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usb iap: correct sample rate descriptors and packet cadence

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Advertise only the implemented 32, 44.1 and 48 kHz stereo formats. Add
128-byte packets at 32 kHz and wrap the 44.1 kHz cadence at ten packets;
a uint8_t wrap at 256 otherwise emits extra samples every cycle.

Use the serialized UAC header length (including baInterfaceNr), maintain
the active alternate setting, accept alt 0 on non-streaming interfaces,
and retain the last valid sample rate when a SET_CUR request is rejected.

Change-Id: I41dab55fc0c7d2e6474492f97062e9838bc3aebf
This commit is contained in:
Paul Sauro 2026-09-20 15:22:15 +02:00
parent e2ee665cce
commit 3bd18f5a44
2 changed files with 19 additions and 14 deletions
Download patch file Download diff file Expand all files Collapse all files

8
firmware/usbstack/iap/audio.c
View file

@ -33,6 +33,7 @@
static const unsigned long samprs[] = {
SAMPR_48,
SAMPR_44,
SAMPR_32,
};
struct StagingBuffer {
@ -83,6 +84,9 @@ static size_t calc_packet_size(uint8_t cur_sampr, uint8_t packet_count) {
if(cur_sampr == 0) {
/*48k*/
return 192;
} else if(cur_sampr == 2) {
/*32k*/
return 128;
} else {
/*44.1k*/
return packet_count % 10 == 0 ? 180 : 176;
@ -100,7 +104,7 @@ start:
if(exhausted || cur_freq != set_freq) {
*ptr = zero_buffer.buf.ptr;
*len = packet_size;
packet_count += 1;
packet_count = (packet_count + 1) % 10;
return;
}
@ -134,7 +138,7 @@ start:
*len = stage->cursor;
stage->cursor = 0;
staging_buffer_index = (staging_buffer_index + 1) % USB_BATCH_SLOTS;
packet_count += 1;
packet_count = (packet_count + 1) % 10;
#if AUDIO_STAT == 1
sample += packet_size / 4;
if(current_tick >= last_hz + HZ) {

25
firmware/usbstack/usb_iap.c
View file

@ -119,23 +119,16 @@ static struct usb_as_interface ipod_audio_stream_1_uac_header = {
.wFormatTag = USB_AS_FORMAT_TYPE_I_PCM,
};
/* TODO: remove unsupported freqs */
static struct usb_as_format_type_i_discrete ipod_audio_stream_1_uac_discrete = {
.bLength = USB_AS_SIZEOF_FORMAT_TYPE_I_DISCRETE(9),
.bLength = USB_AS_SIZEOF_FORMAT_TYPE_I_DISCRETE(3),
.bDescriptorType = USB_DT_CS_INTERFACE,
.bDescriptorSubType = USB_AS_FORMAT_TYPE,
.bFormatType = USB_AS_FORMAT_TYPE_I,
.bNrChannels = 2,
.bSubframeSize = 2, /* bBitResolution / 8 */
.bBitResolution = 16,
.bSamFreqType = 9,
.bSamFreqType = 3,
.tSamFreq = {
{0x40, 0x1F, 0x00}, /* 8000 */
{0x11, 0x2B, 0x00}, /* 11025 */
{0xE0, 0x2E, 0x00}, /* 12000 */
{0x80, 0x3E, 0x00}, /* 16000 */
{0x22, 0x56, 0x00}, /* 22050 */
{0xC0, 0x5D, 0x00}, /* 24000 */
{0x00, 0x7D, 0x00}, /* 32000 */
{0x44, 0xAC, 0x00}, /* 44100 */
{0x80, 0xBB, 0x00}, /* 48000 */
@ -339,7 +332,8 @@ static int usb_iap_get_config_descriptor(unsigned char* dest, int max_packet_siz
PACK_DESC(ipod_audio_control_desc);
ipod_audio_control_uac_header.baInterfaceNr[0] = stream.interface;
ipod_audio_control_uac_header.wTotalLength =
sizeof(ipod_audio_control_uac_header) +
/* sizeof omits the flexible baInterfaceNr array. */
ipod_audio_control_uac_header.bLength +
sizeof(ipod_audio_control_uac_input_terminal) +
sizeof(ipod_audio_control_uac_output_terminal);
PACK_DESC(ipod_audio_control_uac_header);
@ -375,6 +369,7 @@ static int usb_iap_get_config_descriptor(unsigned char* dest, int max_packet_siz
static int usb_iap_init_connection(void) {
stream.sample_rate = 48000;
stream.alt = 0;
last_charge_state = -1;
last_minute = -1;
last_hold_switch_state = -1;
@ -424,6 +419,8 @@ cleanup_audio:
static int usb_iap_set_interface(int intf, int alt) {
LOG("set interface interface=%d alt=%d", intf, alt);
if(intf == ctrl.interface || intf == hid.interface)
return alt == 0 ? 0 : -1;
check_act(intf == stream.interface, return -1);
if(alt == 0) {
check_act(iap_audio_disable(), return -1);
@ -433,11 +430,14 @@ static int usb_iap_set_interface(int intf, int alt) {
ERROR("invalid alt %d", alt);
return -1;
}
stream.alt = alt;
return 0;
}
static int usb_iap_get_interface(int intf) {
LOG("get interface interface=%d", intf);
if(intf == ctrl.interface || intf == hid.interface)
return 0;
check_act(intf == stream.interface, return -1);
return stream.alt;
}
@ -572,9 +572,10 @@ static bool control_request_if_endpoint(struct usb_ctrlrequest* req, uint8_t* re
switch(control_selector) {
case USB_AS_EP_CS_SAMPLING_FREQ_CTL:
check_act(req->wLength == 3, goto stall);
stream.sample_rate = reqdata[0] | (reqdata[1] << 8) | (reqdata[2] << 16);
uint32_t sample_rate = reqdata[0] | (reqdata[1] << 8) | (reqdata[2] << 16);
check_act(iap_audio_set_sampr(sample_rate), goto stall);
stream.sample_rate = sample_rate;
LOG("audio stream sampling rate %lu", stream.sample_rate);
check_act(iap_audio_set_sampr(stream.sample_rate), goto stall);
break;
}
usb_core_control_response(USB_CONTROL_ACK, NULL, 0);