Tinyusb v2.0.0 USB CDC not receiving data (IEC-396)

[Rotario]

Answers checklist.

• I have read the component documentation ESP-IDF Components and the issue is not addressed there.
• I am using target and esp-idf version as defined in component's idf_component.yml
• I have searched the issue tracker for a similar issue and not found any related issue.

Which component are you using? If you choose Other, provide details in More Information.

device/esp_tinyusb

ESP-IDF version.

v5.5.1

Development Kit.

ESP32S3 Custom board

Used Component version.

v2.0.0

More Information.

I downgraded back to v1.7.6 and the data buffer is filling up

[github-actions]

Hi @Rotario! Please be aware that the following suggestions are generated by a bot and haven't been fact-checked by Espressif Systems. We hope that this message will help you until an Espressif Engineer looks at your issue.

---

Thank you for providing detailed information about your setup and the issue. Based on the knowledge sources, here are some key points and suggestions regarding the esp_tinyusb v2.0.0 USB CDC not receiving data:

Key Changes in esp_tinyusb v2.0.0

• Breaking Changes: v2.0.0 introduced several breaking changes, including updates to the CDC-ACM public API and configuration. Specifically, the migration guide for the CDC-ACM class is referenced for details on these changes. It is important to review the CDC-ACM Class Migration guide v2 to ensure your application is updated according to the new API and configuration requirements.
• Endpoint DMA Buffer: v2.0.0 added a configurable parameter for the endpoint DMA buffer in CDC-ACM. If this is not configured correctly, it may affect data reception.
• External PHY Initialization: External PHY is no longer initialized automatically. If your hardware requires an external PHY, you must explicitly initialize it with the configuration parameter phy.skip_setup = true in your code.
• Event Handling: The USB Device event callback mechanism has changed. Make sure you are handling USB Device events as required by the new API, as described in the migration guide and README for esp_tinyusb v2.0.0.

Recommendations

1. Review Migration Guides: Please review the migration guides linked in the esp_tinyusb v2.0.0 release notes, especially for CDC-ACM, to ensure your code is compatible with the new version and that all required configuration changes have been made.
   Espressif's Additions to TinyUSB v2.0.0

2. Check DMA Buffer Configuration: Ensure that the endpoint DMA buffer is configured as required for your application. This is a new configurable parameter in v2.0.0.

3. PHY Initialization: If your board uses an external PHY, make sure you are explicitly initializing it, as it is no longer done automatically.

4. Event Callbacks: Verify that your application is registering and handling the necessary USB Device event callbacks, as the event handling mechanism has changed.

5. Compare with v1.7.6: Since downgrading to v1.7.6 resolves the issue, compare your initialization and configuration code between the two versions, focusing on the changes mentioned above.

If after following the migration guides and updating your configuration the issue persists, please provide a minimal code example that reproduces the problem, along with your CDC-ACM configuration, so further assistance can be provided.

References:

• esp_tinyusb v2.0.0 breaking changes and migration guides
• CDC-ACM configuration and migration

If you need more specific guidance, please share your CDC-ACM initialization code and configuration.

[Rotario]

here's the code

/*

 * SPDX-FileCopyrightText: 2022 Espressif Systems (Shanghai) CO LTD
 *
 * SPDX-License-Identifier: Unlicense OR CC0-1.0
 */

#include <stdint.h>
#include "esp_log.h"
#include "freertos/FreeRTOS.h"
#include "freertos/event_groups.h"
#include "freertos/portmacro.h"
#include "freertos/task.h"

#include "tinyusb.h"

// Define this to use TinyUSB v2.0.0+ API
// Comment out for v1.7.6 and earlier
// #define TINYUSB_V2_API

#ifdef TINYUSB_V2_API
#include "tinyusb_default_config.h"
#else
#include "tusb_cdc_acm.h"
#endif

#include "sdkconfig.h"

#include "config.h"
#include "wifi_connect.h"
 
#define SOH                     (0x01)  /* start of 128-byte data packet */
#define STX                     (0x02)  /* start of 1024-byte data packet */
#define EOT                     (0x04)  /* end of transmission */
#define ACK                     (0x06)  /* acknowledge */
#define NAK                     (0x15)  /* negative acknowledge */
#define CA                      (0x18)  /* two of these in succession aborts transfer */
#define CRC16                   (0x43)  /* 'C' == 0x43, request 16-bit CRC */
#define LF                      (0x0A)  /* LF, bash sends this if echo doesn't have -n flag */
 
#define COMMAND                 (0x10)
static const unsigned char EOL = '\n';
static const char *OK = "OK";
static const char *TAG = "USB";
static uint8_t buf[CONFIG_TINYUSB_CDC_RX_BUFSIZE + 1];
 
static char last_control_char;
static char header[50];
static uint32_t header_counter;
static char packet[2000];
static uint32_t packet_counter;
 
static void reset_uart_state_machine(){
  last_control_char = 0;
  header_counter = 0;
  packet_counter = 0;
}
 
static void send_bytes(int itf, const unsigned char *bytes, size_t bytes_len){
  tinyusb_cdcacm_write_queue(itf, bytes, bytes_len);
  tinyusb_cdcacm_write_queue(itf, &EOL, 1);
  tinyusb_cdcacm_write_flush(itf, 0);
}

#ifdef TINYUSB_V2_API
static void device_event_handler(tinyusb_event_t *event, void *arg)
{
    switch (event->id) {
    case TINYUSB_EVENT_ATTACHED:
        // Device has been attached to the USB Host and configured
        break;
    case TINYUSB_EVENT_DETACHED:
        // Device has been detached from the USB Host
        break;
    default:
        break;
    }
}
#endif
 
 
void tinyusb_cdc_rx_callback(int itf, cdcacm_event_t *event)
{
  /* initialization */
  size_t rx_size = 0;
 
  /* read */
  esp_err_t ret = tinyusb_cdcacm_read(itf, buf, CONFIG_TINYUSB_CDC_RX_BUFSIZE, &rx_size);
  if (ret == ESP_OK) {
    ESP_LOGI(TAG, "Data from channel %d:", itf);
    ESP_LOG_BUFFER_HEXDUMP(TAG, buf, rx_size, ESP_LOG_INFO);
    serial_state_machine(itf, buf, rx_size); // not shared
  } else {
    ESP_LOGE(TAG, "Read error");
  }
}

 
/* void tinyusb_cdc_line_state_changed_callback(int itf, cdcacm_event_t *event) */
/* { */
/*     int dtr = event->line_state_changed_data.dtr; */
/*     int rts = event->line_state_changed_data.rts; */
/*     ESP_LOGI(TAG, "Line state changed on channel %d: DTR:%d, RTS:%d", itf, dtr, rts); */
/* } */
 
static void initialise_usb_cdc_acm(void)
{
  ESP_LOGI(TAG, "USB initialization");

  char const *string_desc_arr[] = {
    (const char[]) { 0x09, 0x04 },  // 0: is supported language is English (0x0409)
    "TrackMyMachines",                      // 1: Manufacturer
    "DataSource v3",               // 2: Product
    Config_get_mac_address(),                       // 3: Serials
    "",                  // 4. MSC
  };

#ifdef TINYUSB_V2_API
  // TinyUSB v2.0.0+ API
  tinyusb_config_t tusb_cfg = TINYUSB_DEFAULT_CONFIG(device_event_handler);
  tusb_cfg.descriptor.string = string_desc_arr;
  tusb_cfg.descriptor.device = NULL;
  tusb_cfg.phy.skip_setup = true;
#else
  // TinyUSB v1.7.6 and earlier API
  const tinyusb_config_t tusb_cfg = {
    .device_descriptor = NULL,
    .string_descriptor = string_desc_arr,
    .external_phy = false,
    .configuration_descriptor = NULL,
  };
#endif

  ESP_ERROR_CHECK(tinyusb_driver_install(&tusb_cfg));

#ifdef TINYUSB_V2_API
  // TinyUSB v2.0.0+ API
  tinyusb_config_cdcacm_t acm_cfg = {
    .cdc_port = TINYUSB_CDC_ACM_0,
    .callback_rx = &tinyusb_cdc_rx_callback,
    .callback_rx_wanted_char = NULL,
    .callback_line_state_changed = NULL,
    .callback_line_coding_changed = NULL
  };
  ESP_ERROR_CHECK(tinyusb_cdcacm_init(&acm_cfg));
#else
  // TinyUSB v1.7.6 and earlier API
  tinyusb_config_cdcacm_t acm_cfg = {
    .usb_dev = TINYUSB_USBDEV_0,
    .cdc_port = TINYUSB_CDC_ACM_0,
    .rx_unread_buf_sz = 64,
    .callback_rx = &tinyusb_cdc_rx_callback,
    .callback_rx_wanted_char = NULL,
    .callback_line_state_changed = NULL,
    .callback_line_coding_changed = NULL
  };
  ESP_ERROR_CHECK(tusb_cdc_acm_init(&acm_cfg));
#endif

  ESP_LOGI(TAG, "USB initialization DONE");
}

void USB_CDC_initialise(void){
  EventBits_t uxBits;
  uxBits = xEventGroupGetBits(Config_event_bits);
  if (uxBits & USB_VCP_BIT){
    ESP_LOGI(TAG, "USB VCP already initialised, can't start CDC");
    return;
  }

#ifdef TINYUSB_V2_API
  if (!tinyusb_cdcacm_initialized(TINYUSB_CDC_ACM_0)){
    initialise_usb_cdc_acm();
  }
#else
  if (!tusb_cdc_acm_initialized(TINYUSB_CDC_ACM_0)){
    initialise_usb_cdc_acm();
  }
#endif
  xEventGroupSetBits(Config_event_bits, USB_CDC_BIT);
}

 
 

[roma-jam]

Hi @Rotario,

in the TinyUSB configuration for v2.0.0 you skip the PHY setup: tusb_cfg.phy.skip_setup = true;

In the configuration for v1.7.6 the PHY in configured internally (because .external_phy = false)

Could you change it to tusb_cfg.phy.skip_setup = false and try again?

[Rotario]

Let me sort that and get back to you - I'm pretty sure I actually fixed that, any other ideas to debug log whilst I do that?

[roma-jam]

@Rotario ,

any other ideas to debug log whilst I do that?

not needed as the CDC driver remains the same.

BTW, if you do not need to configure the device in some specific way, you can just use the default configuration. All the values are handled there already, so you don't need to assign them to NULL explicitly.

[tore-espressif]

@Rotario Is the issue resolved or are there any other questions?

[Rotario]

Hi sorry been crazy will get chance to test this in next couple of days

…

On Tue, 14 Oct 2025, 13:51 Tomas Rezucha, ***@***.***> wrote: *tore-espressif* left a comment (espressif/esp-usb#283) <#283 (comment)> @Rotario <https://github.com/Rotario> Is the issue resolved or are there any other questions? — Reply to this email directly, view it on GitHub <#283 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AHA6QA2CJKOF4B77NBEQMMT3XTWWTAVCNFSM6AAAAACITLAPAKVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZTIMBRGY2TKMZQHA> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[rbliznets]

Perhaps for data size = n*64 callback_rx does not work

[tore-espressif]

Closing due to lack of feedback and inability to reproduce the issue. Feel free to reopen if there are more questions