526 lines
		
	
	
		
			15 KiB
		
	
	
	
		
			C
		
	
	
	
	
	
			
		
		
	
	
			526 lines
		
	
	
		
			15 KiB
		
	
	
	
		
			C
		
	
	
	
	
	
| /*
 | |
|  * The MIT License (MIT)
 | |
|  *
 | |
|  * Copyright (c) 2020 Reinhard Panhuber
 | |
|  * Copyright (c) 2022 HiFiPhile
 | |
|  *
 | |
|  * Permission is hereby granted, free of charge, to any person obtaining a copy
 | |
|  * of this software and associated documentation files (the "Software"), to deal
 | |
|  * in the Software without restriction, including without limitation the rights
 | |
|  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 | |
|  * copies of the Software, and to permit persons to whom the Software is
 | |
|  * furnished to do so, subject to the following conditions:
 | |
|  *
 | |
|  * The above copyright notice and this permission notice shall be included in
 | |
|  * all copies or substantial portions of the Software.
 | |
|  *
 | |
|  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 | |
|  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 | |
|  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 | |
|  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 | |
|  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 | |
|  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 | |
|  * THE SOFTWARE.
 | |
|  *
 | |
|  */
 | |
| 
 | |
| /* plot_audio_samples.py requires following modules:
 | |
|  * $ sudo apt install libportaudio
 | |
|  * $ pip3 install sounddevice matplotlib
 | |
|  *
 | |
|  * Then run
 | |
|  * $ python3 plot_audio_samples.py
 | |
|  */
 | |
| 
 | |
| #include <stdlib.h>
 | |
| #include <stdio.h>
 | |
| #include <string.h>
 | |
| 
 | |
| #include "bsp/board_api.h"
 | |
| #include "tusb.h"
 | |
| #include "usb_descriptors.h"
 | |
| 
 | |
| //--------------------------------------------------------------------+
 | |
| // MACRO CONSTANT TYPEDEF PROTYPES
 | |
| //--------------------------------------------------------------------+
 | |
| 
 | |
| /* Blink pattern
 | |
|  * - 250 ms  : device not mounted
 | |
|  * - 1000 ms : device mounted
 | |
|  * - 2500 ms : device is suspended
 | |
|  */
 | |
| enum  {
 | |
|   BLINK_NOT_MOUNTED = 250,
 | |
|   BLINK_MOUNTED = 1000,
 | |
|   BLINK_SUSPENDED = 2500,
 | |
| };
 | |
| 
 | |
| static uint32_t blink_interval_ms = BLINK_NOT_MOUNTED;
 | |
| 
 | |
| // Audio controls
 | |
| // Current states
 | |
| bool mute[CFG_TUD_AUDIO_FUNC_1_N_CHANNELS_TX + 1]; 				          // +1 for master channel 0
 | |
| uint16_t volume[CFG_TUD_AUDIO_FUNC_1_N_CHANNELS_TX + 1]; 					// +1 for master channel 0
 | |
| uint32_t sampFreq;
 | |
| uint8_t bytesPerSample;
 | |
| uint8_t clkValid;
 | |
| 
 | |
| // Range states
 | |
| // List of supported sample rates
 | |
| static const uint32_t sampleRatesList[] =
 | |
| {
 | |
|     32000, 48000, 96000
 | |
| };
 | |
| 
 | |
| #define N_sampleRates  TU_ARRAY_SIZE(sampleRatesList)
 | |
| 
 | |
| // Bytes per format of every Alt settings
 | |
| static const uint8_t bytesPerSampleAltList[CFG_TUD_AUDIO_FUNC_1_N_FORMATS] =
 | |
| {
 | |
|     CFG_TUD_AUDIO_FUNC_1_FORMAT_1_N_BYTES_PER_SAMPLE_TX,
 | |
|     CFG_TUD_AUDIO_FUNC_1_FORMAT_2_N_BYTES_PER_SAMPLE_TX,
 | |
| };
 | |
| 
 | |
| audio_control_range_2_n_t(1) volumeRng[CFG_TUD_AUDIO_FUNC_1_N_CHANNELS_TX+1]; 			// Volume range state
 | |
| 
 | |
| 
 | |
| // Audio test data
 | |
| CFG_TUSB_MEM_ALIGN uint8_t test_buffer_audio[CFG_TUD_AUDIO_FUNC_1_EP_IN_SZ_MAX];
 | |
| uint16_t startVal = 0;
 | |
| 
 | |
| void led_blinking_task(void);
 | |
| void audio_task(void);
 | |
| 
 | |
| /*------------- MAIN -------------*/
 | |
| int main(void)
 | |
| {
 | |
|   board_init();
 | |
| 
 | |
|   // init device stack on configured roothub port
 | |
|   tud_init(BOARD_TUD_RHPORT);
 | |
| 
 | |
|   if (board_init_after_tusb) {
 | |
|     board_init_after_tusb();
 | |
|   }
 | |
| 
 | |
|   // Init values
 | |
|   sampFreq = sampleRatesList[0];
 | |
|   clkValid = 1;
 | |
| 
 | |
|   while (1)
 | |
|   {
 | |
|     tud_task(); // tinyusb device task
 | |
|     led_blinking_task();
 | |
|     audio_task();
 | |
|   }
 | |
| 
 | |
| 
 | |
|   return 0;
 | |
| }
 | |
| 
 | |
| //--------------------------------------------------------------------+
 | |
| // Device callbacks
 | |
| //--------------------------------------------------------------------+
 | |
| 
 | |
| // Invoked when device is mounted
 | |
| void tud_mount_cb(void)
 | |
| {
 | |
|   blink_interval_ms = BLINK_MOUNTED;
 | |
| }
 | |
| 
 | |
| // Invoked when device is unmounted
 | |
| void tud_umount_cb(void)
 | |
| {
 | |
|   blink_interval_ms = BLINK_NOT_MOUNTED;
 | |
| }
 | |
| 
 | |
| // Invoked when usb bus is suspended
 | |
| // remote_wakeup_en : if host allow us  to perform remote wakeup
 | |
| // Within 7ms, device must draw an average of current less than 2.5 mA from bus
 | |
| void tud_suspend_cb(bool remote_wakeup_en)
 | |
| {
 | |
|   (void) remote_wakeup_en;
 | |
|   blink_interval_ms = BLINK_SUSPENDED;
 | |
| }
 | |
| 
 | |
| // Invoked when usb bus is resumed
 | |
| void tud_resume_cb(void)
 | |
| {
 | |
|   blink_interval_ms = tud_mounted() ? BLINK_MOUNTED : BLINK_NOT_MOUNTED;
 | |
| }
 | |
| 
 | |
| //--------------------------------------------------------------------+
 | |
| // AUDIO Task
 | |
| //--------------------------------------------------------------------+
 | |
| 
 | |
| void audio_task(void)
 | |
| {
 | |
|   // Yet to be filled - e.g. put meas data into TX FIFOs etc.
 | |
|   // asm("nop");
 | |
| }
 | |
| 
 | |
| //--------------------------------------------------------------------+
 | |
| // Application Callback API Implementations
 | |
| //--------------------------------------------------------------------+
 | |
| 
 | |
| // Invoked when set interface is called, typically on start/stop streaming or format change
 | |
| bool tud_audio_set_itf_cb(uint8_t rhport, tusb_control_request_t const * p_request)
 | |
| {
 | |
|   (void)rhport;
 | |
|   //uint8_t const itf = tu_u16_low(tu_le16toh(p_request->wIndex));
 | |
|   uint8_t const alt = tu_u16_low(tu_le16toh(p_request->wValue));
 | |
| 
 | |
|   // Clear buffer when streaming format is changed
 | |
|   if(alt != 0)
 | |
|   {
 | |
|     bytesPerSample = bytesPerSampleAltList[alt-1];
 | |
|   }
 | |
|   return true;
 | |
| }
 | |
| 
 | |
| // Invoked when audio class specific set request received for an EP
 | |
| bool tud_audio_set_req_ep_cb(uint8_t rhport, tusb_control_request_t const * p_request, uint8_t *pBuff)
 | |
| {
 | |
|   (void) rhport;
 | |
|   (void) pBuff;
 | |
| 
 | |
|   // We do not support any set range requests here, only current value requests
 | |
|   TU_VERIFY(p_request->bRequest == AUDIO_CS_REQ_CUR);
 | |
| 
 | |
|   // Page 91 in UAC2 specification
 | |
|   uint8_t channelNum = TU_U16_LOW(p_request->wValue);
 | |
|   uint8_t ctrlSel = TU_U16_HIGH(p_request->wValue);
 | |
|   uint8_t ep = TU_U16_LOW(p_request->wIndex);
 | |
| 
 | |
|   (void) channelNum; (void) ctrlSel; (void) ep;
 | |
| 
 | |
|   return false; 	// Yet not implemented
 | |
| }
 | |
| 
 | |
| // Invoked when audio class specific set request received for an interface
 | |
| bool tud_audio_set_req_itf_cb(uint8_t rhport, tusb_control_request_t const * p_request, uint8_t *pBuff)
 | |
| {
 | |
|   (void) rhport;
 | |
|   (void) pBuff;
 | |
| 
 | |
|   // We do not support any set range requests here, only current value requests
 | |
|   TU_VERIFY(p_request->bRequest == AUDIO_CS_REQ_CUR);
 | |
| 
 | |
|   // Page 91 in UAC2 specification
 | |
|   uint8_t channelNum = TU_U16_LOW(p_request->wValue);
 | |
|   uint8_t ctrlSel = TU_U16_HIGH(p_request->wValue);
 | |
|   uint8_t itf = TU_U16_LOW(p_request->wIndex);
 | |
| 
 | |
|   (void) channelNum; (void) ctrlSel; (void) itf;
 | |
| 
 | |
|   return false; 	// Yet not implemented
 | |
| }
 | |
| 
 | |
| // Invoked when audio class specific set request received for an entity
 | |
| bool tud_audio_set_req_entity_cb(uint8_t rhport, tusb_control_request_t const * p_request, uint8_t *pBuff)
 | |
| {
 | |
|   (void) rhport;
 | |
| 
 | |
|   // Page 91 in UAC2 specification
 | |
|   uint8_t channelNum = TU_U16_LOW(p_request->wValue);
 | |
|   uint8_t ctrlSel = TU_U16_HIGH(p_request->wValue);
 | |
|   uint8_t itf = TU_U16_LOW(p_request->wIndex);
 | |
|   uint8_t entityID = TU_U16_HIGH(p_request->wIndex);
 | |
| 
 | |
|   (void) itf;
 | |
| 
 | |
|   // We do not support any set range requests here, only current value requests
 | |
|   TU_VERIFY(p_request->bRequest == AUDIO_CS_REQ_CUR);
 | |
| 
 | |
|   // If request is for our feature unit
 | |
|   if ( entityID == UAC2_ENTITY_FEATURE_UNIT )
 | |
|   {
 | |
|     switch ( ctrlSel )
 | |
|     {
 | |
|       case AUDIO_FU_CTRL_MUTE:
 | |
|         // Request uses format layout 1
 | |
|         TU_VERIFY(p_request->wLength == sizeof(audio_control_cur_1_t));
 | |
| 
 | |
|         mute[channelNum] = ((audio_control_cur_1_t*) pBuff)->bCur;
 | |
| 
 | |
|         TU_LOG2("    Set Mute: %d of channel: %u\r\n", mute[channelNum], channelNum);
 | |
|       return true;
 | |
| 
 | |
|       case AUDIO_FU_CTRL_VOLUME:
 | |
|         // Request uses format layout 2
 | |
|         TU_VERIFY(p_request->wLength == sizeof(audio_control_cur_2_t));
 | |
| 
 | |
|         volume[channelNum] = (uint16_t) ((audio_control_cur_2_t*) pBuff)->bCur;
 | |
| 
 | |
|         TU_LOG2("    Set Volume: %d dB of channel: %u\r\n", volume[channelNum], channelNum);
 | |
|       return true;
 | |
| 
 | |
|         // Unknown/Unsupported control
 | |
|       default:
 | |
|         TU_BREAKPOINT();
 | |
|       return false;
 | |
|     }
 | |
|   }
 | |
| 
 | |
|   // Clock Source unit
 | |
|   if ( entityID == UAC2_ENTITY_CLOCK )
 | |
|   {
 | |
|     switch ( ctrlSel )
 | |
|     {
 | |
|       case AUDIO_CS_CTRL_SAM_FREQ:
 | |
|         TU_VERIFY(p_request->wLength == sizeof(audio_control_cur_4_t));
 | |
| 
 | |
|         sampFreq = (uint32_t)((audio_control_cur_4_t *)pBuff)->bCur;
 | |
| 
 | |
|         TU_LOG2("Clock set current freq: %lu\r\n", sampFreq);
 | |
| 
 | |
|         return true;
 | |
|       break;
 | |
| 
 | |
|       // Unknown/Unsupported control
 | |
|       default:
 | |
|         TU_BREAKPOINT();
 | |
|         return false;
 | |
|     }
 | |
|   }
 | |
| 
 | |
|   return false;    // Yet not implemented
 | |
| }
 | |
| 
 | |
| // Invoked when audio class specific get request received for an EP
 | |
| bool tud_audio_get_req_ep_cb(uint8_t rhport, tusb_control_request_t const * p_request)
 | |
| {
 | |
|   (void) rhport;
 | |
| 
 | |
|   // Page 91 in UAC2 specification
 | |
|   uint8_t channelNum = TU_U16_LOW(p_request->wValue);
 | |
|   uint8_t ctrlSel = TU_U16_HIGH(p_request->wValue);
 | |
|   uint8_t ep = TU_U16_LOW(p_request->wIndex);
 | |
| 
 | |
|   (void) channelNum; (void) ctrlSel; (void) ep;
 | |
| 
 | |
|   //	return tud_control_xfer(rhport, p_request, &tmp, 1);
 | |
| 
 | |
|   return false; 	// Yet not implemented
 | |
| }
 | |
| 
 | |
| // Invoked when audio class specific get request received for an interface
 | |
| bool tud_audio_get_req_itf_cb(uint8_t rhport, tusb_control_request_t const * p_request)
 | |
| {
 | |
|   (void) rhport;
 | |
| 
 | |
|   // Page 91 in UAC2 specification
 | |
|   uint8_t channelNum = TU_U16_LOW(p_request->wValue);
 | |
|   uint8_t ctrlSel = TU_U16_HIGH(p_request->wValue);
 | |
|   uint8_t itf = TU_U16_LOW(p_request->wIndex);
 | |
| 
 | |
|   (void) channelNum; (void) ctrlSel; (void) itf;
 | |
| 
 | |
|   return false; 	// Yet not implemented
 | |
| }
 | |
| 
 | |
| // Invoked when audio class specific get request received for an entity
 | |
| bool tud_audio_get_req_entity_cb(uint8_t rhport, tusb_control_request_t const * p_request)
 | |
| {
 | |
|   (void) rhport;
 | |
| 
 | |
|   // Page 91 in UAC2 specification
 | |
|   uint8_t channelNum = TU_U16_LOW(p_request->wValue);
 | |
|   uint8_t ctrlSel = TU_U16_HIGH(p_request->wValue);
 | |
|   // uint8_t itf = TU_U16_LOW(p_request->wIndex); 			// Since we have only one audio function implemented, we do not need the itf value
 | |
|   uint8_t entityID = TU_U16_HIGH(p_request->wIndex);
 | |
| 
 | |
|   // Input terminal (Microphone input)
 | |
|   if (entityID == UAC2_ENTITY_INPUT_TERMINAL)
 | |
|   {
 | |
|     switch ( ctrlSel )
 | |
|     {
 | |
|       case AUDIO_TE_CTRL_CONNECTOR:
 | |
|       {
 | |
|         // The terminal connector control only has a get request with only the CUR attribute.
 | |
|         audio_desc_channel_cluster_t ret;
 | |
| 
 | |
|         // Those are dummy values for now
 | |
|         ret.bNrChannels = 1;
 | |
|         ret.bmChannelConfig = 0;
 | |
|         ret.iChannelNames = 0;
 | |
| 
 | |
|         TU_LOG2("    Get terminal connector\r\n");
 | |
| 
 | |
|         return tud_audio_buffer_and_schedule_control_xfer(rhport, p_request, (void*) &ret, sizeof(ret));
 | |
|       }
 | |
|       break;
 | |
| 
 | |
|         // Unknown/Unsupported control selector
 | |
|       default:
 | |
|         TU_BREAKPOINT();
 | |
|         return false;
 | |
|     }
 | |
|   }
 | |
| 
 | |
|   // Feature unit
 | |
|   if (entityID == UAC2_ENTITY_FEATURE_UNIT)
 | |
|   {
 | |
|     switch ( ctrlSel )
 | |
|     {
 | |
|       case AUDIO_FU_CTRL_MUTE:
 | |
|         // Audio control mute cur parameter block consists of only one byte - we thus can send it right away
 | |
|         // There does not exist a range parameter block for mute
 | |
|         TU_LOG2("    Get Mute of channel: %u\r\n", channelNum);
 | |
|         return tud_control_xfer(rhport, p_request, &mute[channelNum], 1);
 | |
| 
 | |
|       case AUDIO_FU_CTRL_VOLUME:
 | |
|         switch ( p_request->bRequest )
 | |
|         {
 | |
|           case AUDIO_CS_REQ_CUR:
 | |
|             TU_LOG2("    Get Volume of channel: %u\r\n", channelNum);
 | |
|             return tud_control_xfer(rhport, p_request, &volume[channelNum], sizeof(volume[channelNum]));
 | |
| 
 | |
|           case AUDIO_CS_REQ_RANGE:
 | |
|             TU_LOG2("    Get Volume range of channel: %u\r\n", channelNum);
 | |
| 
 | |
|             // Copy values - only for testing - better is version below
 | |
|             audio_control_range_2_n_t(1)
 | |
|             ret;
 | |
| 
 | |
|             ret.wNumSubRanges = 1;
 | |
|             ret.subrange[0].bMin = -90;    // -90 dB
 | |
|             ret.subrange[0].bMax = 30;		// +30 dB
 | |
|             ret.subrange[0].bRes = 1; 		// 1 dB steps
 | |
| 
 | |
|             return tud_audio_buffer_and_schedule_control_xfer(rhport, p_request, (void*) &ret, sizeof(ret));
 | |
| 
 | |
|             // Unknown/Unsupported control
 | |
|           default:
 | |
|             TU_BREAKPOINT();
 | |
|             return false;
 | |
|         }
 | |
|       break;
 | |
| 
 | |
|         // Unknown/Unsupported control
 | |
|       default:
 | |
|         TU_BREAKPOINT();
 | |
|         return false;
 | |
|     }
 | |
|   }
 | |
| 
 | |
|   // Clock Source unit
 | |
|   if ( entityID == UAC2_ENTITY_CLOCK )
 | |
|   {
 | |
|     switch ( ctrlSel )
 | |
|     {
 | |
|       case AUDIO_CS_CTRL_SAM_FREQ:
 | |
|         // channelNum is always zero in this case
 | |
|         switch ( p_request->bRequest )
 | |
|         {
 | |
|           case AUDIO_CS_REQ_CUR:
 | |
|             TU_LOG2("    Get Sample Freq.\r\n");
 | |
|             return tud_control_xfer(rhport, p_request, &sampFreq, sizeof(sampFreq));
 | |
| 
 | |
|           case AUDIO_CS_REQ_RANGE:
 | |
|           {
 | |
|             TU_LOG2("    Get Sample Freq. range\r\n");
 | |
|             audio_control_range_4_n_t(N_sampleRates) rangef =
 | |
|             {
 | |
|                 .wNumSubRanges = tu_htole16(N_sampleRates)
 | |
|             };
 | |
|             TU_LOG1("Clock get %d freq ranges\r\n", N_sampleRates);
 | |
|             for(uint8_t i = 0; i < N_sampleRates; i++)
 | |
|             {
 | |
|                 rangef.subrange[i].bMin = (int32_t)sampleRatesList[i];
 | |
|                 rangef.subrange[i].bMax = (int32_t)sampleRatesList[i];
 | |
|                 rangef.subrange[i].bRes = 0;
 | |
|                 TU_LOG1("Range %d (%d, %d, %d)\r\n", i, (int)rangef.subrange[i].bMin, (int)rangef.subrange[i].bMax, (int)rangef.subrange[i].bRes);
 | |
|             }
 | |
|             return tud_audio_buffer_and_schedule_control_xfer(rhport, p_request, &rangef, sizeof(rangef));
 | |
|           }
 | |
|            // Unknown/Unsupported control
 | |
|           default:
 | |
|             TU_BREAKPOINT();
 | |
|             return false;
 | |
|         }
 | |
|       break;
 | |
| 
 | |
|       case AUDIO_CS_CTRL_CLK_VALID:
 | |
|         // Only cur attribute exists for this request
 | |
|         TU_LOG2("    Get Sample Freq. valid\r\n");
 | |
|         return tud_control_xfer(rhport, p_request, &clkValid, sizeof(clkValid));
 | |
| 
 | |
|       // Unknown/Unsupported control
 | |
|       default:
 | |
|         TU_BREAKPOINT();
 | |
|         return false;
 | |
|     }
 | |
|   }
 | |
| 
 | |
|   TU_LOG2("  Unsupported entity: %d\r\n", entityID);
 | |
|   return false; 	// Yet not implemented
 | |
| }
 | |
| 
 | |
| bool tud_audio_tx_done_pre_load_cb(uint8_t rhport, uint8_t itf, uint8_t ep_in, uint8_t cur_alt_setting)
 | |
| {
 | |
|   (void) rhport;
 | |
|   (void) itf;
 | |
|   (void) ep_in;
 | |
|   (void) cur_alt_setting;
 | |
| 
 | |
|   tud_audio_write((uint8_t *)test_buffer_audio, (uint16_t)(sampFreq / (TUD_OPT_HIGH_SPEED ? 8000 : 1000) * bytesPerSample));
 | |
| 
 | |
|   return true;
 | |
| }
 | |
| 
 | |
| bool tud_audio_tx_done_post_load_cb(uint8_t rhport, uint16_t n_bytes_copied, uint8_t itf, uint8_t ep_in, uint8_t cur_alt_setting)
 | |
| {
 | |
|   (void) rhport;
 | |
|   (void) n_bytes_copied;
 | |
|   (void) itf;
 | |
|   (void) ep_in;
 | |
|   (void) cur_alt_setting;
 | |
| 
 | |
|   // 16bit
 | |
|   if(bytesPerSample == 2)
 | |
|   {
 | |
|     uint16_t* pData_16 = (uint16_t*)((void*)test_buffer_audio);
 | |
|     for (size_t cnt = 0; cnt < sampFreq / (TUD_OPT_HIGH_SPEED ? 8000 : 1000); cnt++)
 | |
|     {
 | |
|       pData_16[cnt] = startVal++;
 | |
|     }
 | |
|   }
 | |
|   // 24bit in 32bit slot
 | |
|   else if(bytesPerSample == 4)
 | |
|   {
 | |
|     uint32_t* pData_32 = (uint32_t*)((void*)test_buffer_audio);
 | |
|     for (size_t cnt = 0; cnt < sampFreq / (TUD_OPT_HIGH_SPEED ? 8000 : 1000); cnt++)
 | |
|     {
 | |
|       pData_32[cnt] = (uint32_t)startVal++ << 16U;
 | |
|     }
 | |
|   }
 | |
| 
 | |
|   return true;
 | |
| }
 | |
| 
 | |
| bool tud_audio_set_itf_close_EP_cb(uint8_t rhport, tusb_control_request_t const * p_request)
 | |
| {
 | |
|   (void) rhport;
 | |
|   (void) p_request;
 | |
|   startVal = 0;
 | |
| 
 | |
|   return true;
 | |
| }
 | |
| 
 | |
| //--------------------------------------------------------------------+
 | |
| // BLINKING TASK
 | |
| //--------------------------------------------------------------------+
 | |
| void led_blinking_task(void)
 | |
| {
 | |
|   static uint32_t start_ms = 0;
 | |
|   static bool led_state = false;
 | |
| 
 | |
|   // Blink every interval ms
 | |
|   if ( board_millis() - start_ms < blink_interval_ms) return; // not enough time
 | |
|   start_ms += blink_interval_ms;
 | |
| 
 | |
|   board_led_write(led_state);
 | |
|   led_state = 1 - led_state; // toggle
 | |
| }
 | 
