Hi everyone,
I believe that the documentation has an off by 1 error.
"The MTU includes the SLIP encapsulation, which means that the maximum data size that can be sent is (MTU/2) - 2."
https://docs.nordicsemi.com/bundle/nrf5_SDK_v17.1.1/page/lib_dfu_transport_serial.html
If we plug in MTU=2051 into the equation we get 1023.5, which seemed off to me.
Since max_size during firmware image transfer is 4096, the value of 1024 seemed to be more appropriate.
After looking through the nordic device side code I found this file:
nordic\DeviceDownload\nRF5_SDK_17.1.0_ddde560\components\libraries\bootloader\serial_dfu\nrf_dfu_serial_usb.c
#define RX_BUF_SIZE (1024)
#define SLIP_MTU (2 * (RX_BUF_SIZE + 1) + 1)
Which shows us that the value is not 1023.5, but exactly 1024.
Kind regards,
Strongato
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#include <string.h>
#include "nrf_dfu_req_handler.h"
#include "nrf_dfu_transport.h"
#include "slip.h"
#include "nrf_balloc.h"
#include "nrf_drv_power.h"
#include "nrf_drv_clock.h"
#include "nrf_drv_usbd.h"
#include "nrf_dfu_serial.h"
#include "app_scheduler.h"
#include "app_usbd.h"
#include "app_usbd_cdc_acm.h"
#include "app_usbd_core.h"
#include "app_usbd_string_desc.h"
#include "app_util_platform.h"
#include "app_usbd_serial_num.h"
#define NRF_LOG_MODULE_NAME nrf_dfu_serial_usb
#include "nrf_log.h"
NRF_LOG_MODULE_REGISTER();
/**@file
*
* @defgroup nrf_dfu_serial_usb DFU Serial USB CDC ACM transport
* @ingroup nrf_dfu
* @brief Device Firmware Update (DFU) transport layer using USB CDC ACM.
*/
#define NRF_SERIAL_OPCODE_SIZE (sizeof(uint8_t))
#define NRF_USB_MAX_RESPONSE_SIZE_SLIP (2 * NRF_SERIAL_MAX_RESPONSE_SIZE + 1)
#define RX_BUF_SIZE (1024)
#define SLIP_MTU (2 * (RX_BUF_SIZE + 1) + 1)
#define OPCODE_OFFSET (sizeof(uint32_t) - NRF_SERIAL_OPCODE_SIZE)
#define DATA_OFFSET (OPCODE_OFFSET + NRF_SERIAL_OPCODE_SIZE)
#define CDC_ACM_COMM_INTERFACE 0
#define CDC_ACM_COMM_EPIN NRF_DRV_USBD_EPIN2
#define CDC_ACM_DATA_INTERFACE 1
#define CDC_ACM_DATA_EPIN NRF_DRV_USBD_EPIN1
#define CDC_ACM_DATA_EPOUT NRF_DRV_USBD_EPOUT1
/**
* @brief Enable power USB detection
*
* Configure if example supports USB port connection
*/
#ifndef USBD_POWER_DETECTION
#define USBD_POWER_DETECTION true
#endif
/**
* @brief Interfaces list passed to @ref APP_USBD_CDC_ACM_GLOBAL_DEF
* */
#define CDC_ACM_INTERFACES_CONFIG() \
APP_USBD_CDC_ACM_CONFIG(CDC_ACM_COMM_INTERFACE, \
CDC_ACM_COMM_EPIN, \
CDC_ACM_DATA_INTERFACE, \
CDC_ACM_DATA_EPIN, \
CDC_ACM_DATA_EPOUT)
/*lint -save -e26 -e64 -e505 -e651 */
static void cdc_acm_user_ev_handler(app_usbd_class_inst_t const * p_inst,
app_usbd_cdc_acm_user_event_t event);
/**@brief CDC_ACM class instance. */
APP_USBD_CDC_ACM_GLOBAL_DEF(m_app_cdc_acm,
cdc_acm_user_ev_handler,
CDC_ACM_COMM_INTERFACE,
CDC_ACM_DATA_INTERFACE,
CDC_ACM_COMM_EPIN,
CDC_ACM_DATA_EPIN,
CDC_ACM_DATA_EPOUT,
APP_USBD_CDC_COMM_PROTOCOL_NONE);
/*lint -restore */
NRF_BALLOC_DEF(m_payload_pool, (SLIP_MTU+1), NRF_DFU_SERIAL_USB_RX_BUFFERS);
static nrf_dfu_serial_t m_serial;
static slip_t m_slip;
static uint8_t m_rsp_buf[NRF_USB_MAX_RESPONSE_SIZE_SLIP];
static uint8_t m_rx_buf[NRF_DRV_USBD_EPSIZE];
static nrf_dfu_observer_t m_observer;
static uint32_t usb_dfu_transport_init(nrf_dfu_observer_t observer);
static uint32_t usb_dfu_transport_close(nrf_dfu_transport_t const * p_exception);
DFU_TRANSPORT_REGISTER(nrf_dfu_transport_t const usb_dfu_transport) =
{
.init_func = usb_dfu_transport_init,
.close_func = usb_dfu_transport_close,
};
static void payload_free(void * p_buf)
{
uint8_t * p_buf_root = ((uint8_t *)(p_buf)) - DATA_OFFSET; //pointer is shifted to point to data
nrf_balloc_free(&m_payload_pool, p_buf_root);
}
static ret_code_t rsp_send(uint8_t const * p_data, uint32_t length)
{
ASSERT(p_data);
ASSERT(length != 0);
uint32_t slip_len;
// Cannot fail if inputs are non-NULL.
(void) slip_encode(m_rsp_buf, (uint8_t *)(p_data), length, &slip_len);
return app_usbd_cdc_acm_write(&m_app_cdc_acm, m_rsp_buf, slip_len);
}
static void on_rx_complete(nrf_dfu_serial_t * p_transport, uint8_t * p_data, uint8_t len)
{
ret_code_t ret_code;
for (uint32_t i = 0; i < len; i++)
{
ret_code = slip_decode_add_byte(&m_slip, p_data[i]);
if (ret_code != NRF_SUCCESS)
{
continue;
}
nrf_dfu_serial_on_packet_received(p_transport,
(uint8_t const *)(m_slip.p_buffer),
m_slip.current_index);
uint8_t * p_rx_buf = nrf_balloc_alloc(&m_payload_pool);
if (p_rx_buf == NULL)
{
NRF_LOG_ERROR("Failed to allocate buffer!");
return;
}
NRF_LOG_DEBUG("Allocated buffer %x", p_rx_buf);
// reset the slip decoding
m_slip.p_buffer = &p_rx_buf[OPCODE_OFFSET];
m_slip.current_index = 0;
m_slip.state = SLIP_STATE_DECODING;
}
}
/**
* @brief User event handler @ref app_usbd_cdc_acm_user_ev_handler_t (headphones)
* */
static void cdc_acm_user_ev_handler(app_usbd_class_inst_t const * p_inst,
app_usbd_cdc_acm_user_event_t event)
{
ret_code_t ret_code;
switch (event)
{
case APP_USBD_CDC_ACM_USER_EVT_PORT_OPEN:
{
ret_code = app_usbd_cdc_acm_read(&m_app_cdc_acm, m_rx_buf, 1);
NRF_LOG_WARNING("Could not read from CDC. Error: 0x%x.", ret_code);
} break;
case APP_USBD_CDC_ACM_USER_EVT_RX_DONE:
{
do
{
on_rx_complete(&m_serial, m_rx_buf, 1);
ret_code = app_usbd_cdc_acm_read(&m_app_cdc_acm, m_rx_buf, 1);
} while (ret_code == NRF_SUCCESS);
} break;
default:
break;
}
}
static void usbd_dfu_transport_ev_handler(app_usbd_event_type_t event)
{
switch (event)
{
case APP_USBD_EVT_STOPPED:
app_usbd_disable();
break;
case APP_USBD_EVT_POWER_DETECTED:
NRF_LOG_INFO("USB power detected");
if (!nrf_drv_usbd_is_enabled())
{
app_usbd_enable();
}
if (m_observer)
{
m_observer(NRF_DFU_EVT_TRANSPORT_ACTIVATED);
}
break;
case APP_USBD_EVT_POWER_REMOVED:
NRF_LOG_INFO("USB power removed");
app_usbd_stop();
if (m_observer)
{
m_observer(NRF_DFU_EVT_TRANSPORT_DEACTIVATED);
}
break;
case APP_USBD_EVT_POWER_READY:
NRF_LOG_INFO("USB ready");
app_usbd_start();
break;
default:
break;
}
}
static void usbd_sched_event_handler(void * p_event_data, uint16_t event_size)
{
app_usbd_event_execute(p_event_data);
}
static void usbd_event_handler(app_usbd_internal_evt_t const * const p_event)
{
ret_code_t ret_code;
if (p_event->type == APP_USBD_EVT_DRV_SOF)
{
app_usbd_event_execute(p_event);
}
else
{
ret_code = app_sched_event_put(p_event,
sizeof(app_usbd_internal_evt_t),
usbd_sched_event_handler);
if (ret_code != NRF_SUCCESS)
{
NRF_LOG_ERROR("Could not schedule USB event!");
}
}
}
static uint32_t usb_dfu_transport_init(nrf_dfu_observer_t observer)
{
uint32_t err_code;
/* Execute event directly in interrupt handler */
static const app_usbd_config_t usbd_config =
{
.ev_handler = usbd_event_handler,
.ev_state_proc = usbd_dfu_transport_ev_handler
};
(void) nrf_balloc_init(&m_payload_pool); //Result is checked by checking result of _alloc().
m_observer = observer;
uint8_t * p_rx_buf = nrf_balloc_alloc(&m_payload_pool);
if (p_rx_buf == NULL)
{
NRF_LOG_ERROR("Could not allocate payload pool.");
return NRF_ERROR_INTERNAL;
}
m_slip.p_buffer = &p_rx_buf[OPCODE_OFFSET];
m_slip.current_index = 0;
m_slip.buffer_len = SLIP_MTU;
m_slip.state = SLIP_STATE_DECODING;
m_serial.rsp_func = rsp_send;
m_serial.payload_free_func = payload_free;
m_serial.mtu = SLIP_MTU;
m_serial.p_rsp_buf = &m_rsp_buf[NRF_USB_MAX_RESPONSE_SIZE_SLIP -
NRF_SERIAL_MAX_RESPONSE_SIZE];
m_serial.p_low_level_transport = &usb_dfu_transport;
NRF_LOG_DEBUG("Initializing drivers.");
err_code = nrf_drv_clock_init();
if (err_code != NRF_ERROR_MODULE_ALREADY_INITIALIZED)
{
VERIFY_SUCCESS(err_code);
}
err_code = nrf_drv_power_init(NULL);
VERIFY_SUCCESS(err_code);
app_usbd_serial_num_generate();
err_code = app_usbd_init(&usbd_config);
VERIFY_SUCCESS(err_code);
app_usbd_class_inst_t const * class_cdc_acm = app_usbd_cdc_acm_class_inst_get(&m_app_cdc_acm);
err_code = app_usbd_class_append(class_cdc_acm);
VERIFY_SUCCESS(err_code);
NRF_LOG_DEBUG("Starting USB");
if (USBD_POWER_DETECTION)
{
err_code = app_usbd_power_events_enable();
VERIFY_SUCCESS(err_code);
}
else
{
NRF_LOG_DEBUG("No USB power detection enabled, starting USB now");
app_usbd_enable();
app_usbd_start();
}
NRF_LOG_DEBUG("USB Transport initialized");
return err_code;
}
static uint32_t usb_dfu_transport_close(nrf_dfu_transport_t const * p_exception)
{
return NRF_SUCCESS;
}
