Need help finding documentation or tutorial that explains USB CDC ACM.

[Jerry Easley]

I want to create a virtual com port on my pc from my nRF52840 dongle program. And direct the output of printx statements to it so I can monitor it with putty.

I have tried very diligently to search for this information on your website; I get covered up with hits, all, seemingly irrelevant. For the life of me I don't understand how anyone ever finds anything in your documentation.  I can search on terms like "nRF52 USB CDC ACM tutorial" and your search engine ignores the quotes and I get over 700 hits.

I have also tried to search your examples for this information with no success.  Why is it so dang hard to find information here?

Jerry

[Jerry Easley]

The following is a program from the BLE tutorial; I post it here because it does what I want to in that it causes the device driver on my PC to create a virtual com port, COM10, and directs the output of the printk statements to it.  I have carefully gone through the code but I can't figure out how it works, can someone explain how this works?

/*
* Copyright (c) 2023 Nordic Semiconductor ASA
*
* SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
*/

#include <zephyr/kernel.h>
#include <zephyr/logging/log.h>
#include <zephyr/bluetooth/bluetooth.h>
#include <zephyr/bluetooth/gap.h>
#include <dk_buttons_and_leds.h>

/* STEP 2.1 - Declare the Company identifier (Company ID) */
#define COMPANY_ID_CODE 0x0059

/* STEP 2.2 - Declare the structure for your custom data */
typedef struct adv_mfg_data {
uint16_t company_code; /* Company Identifier Code. */
uint16_t number_press; /* Number of times Button 1 is pressed*/
} adv_mfg_data_type;

#define USER_BUTTON DK_BTN1_MSK

/* STEP 1 - Create an LE Advertising Parameters variable */
static struct bt_le_adv_param *adv_param = BT_LE_ADV_PARAM(BT_LE_ADV_OPT_NONE, /* No options spesified*/
800, /*Min Advertising Interval 500ms (800*0.625ms) */
801, /*Max Advertising Interval 500.625ms (801*0.625ms)*/
NULL); /* Set to NULL for undirected advertising*/

/* STEP 2.3 - Define and initialize a variable of type adv_mfg_data_type */
static adv_mfg_data_type adv_mfg_data = {COMPANY_ID_CODE,0x00};

static unsigned char url_data[] ={0x17,'/','/','a','c','a','d','e','m','y','.','n','o','r','d','i','c','s'
LOG_MODULE_REGISTER(Lesson2_Exercise2, LOG_LEVEL_INF);

#define DEVICE_NAME CONFIG_BT_DEVICE_NAME
#define DEVICE_NAME_LEN (sizeof(DEVICE_NAME) - 1)

#define RUN_STATUS_LED DK_LED1
#define RUN_LED_BLINK_INTERVAL 1000

static const struct bt_data ad[] = {
BT_DATA_BYTES(BT_DATA_FLAGS, BT_LE_AD_NO_BREDR),
BT_DATA(BT_DATA_NAME_COMPLETE, DEVICE_NAME, DEVICE_NAME_LEN),
/* STEP 3 - Include the Manufacturer Specific Data in the advertising packet. */
BT_DATA(BT_DATA_MANUFACTURER_DATA,(unsigned char *)&adv_mfg_data, sizeof(adv_mfg_data)),
};

static const struct bt_data sd[] = {
BT_DATA(BT_DATA_URI, url_data,sizeof(url_data)),
};
/* STEP 5 - Add the definition of callback function and update the advertising data dynamically */
static void button_changed(uint32_t button_state, uint32_t has_changed)
{
printk("Button Pressed, button_state = %d, has_changed = %d USER_BUTTON = %d, adv_mfg_data.number_pres
if (has_changed & button_state & USER_BUTTON) {
adv_mfg_data.number_press += 1;
bt_le_adv_update_data(ad, ARRAY_SIZE(ad),
sd, ARRAY_SIZE(sd));
}
}
/* STEP 4.1 - Define the initialization function of the buttons and setup interrupt. */
static int init_button(void)
{
int err;

err = dk_buttons_init(button_changed);
if (err) {
printk("Cannot init buttons (err: %d)\n", err);
}

return err;
}

void main(void)
{
int blink_status = 0;
int err;

LOG_INF("Starting Lesson 2 - Exercise 1 \n");

err = dk_leds_init();
if (err) {
LOG_ERR("LEDs init failed (err %d)\n", err);
return;
}
/* STEP 4.2 - Setup buttons on your board */
err = init_button();
if (err) {
printk("Button init failed (err %d)\n", err);
return;
}

err = bt_enable(NULL);
if (err) {
LOG_ERR("Bluetooth init failed (err %d)\n", err);
return;
}

LOG_INF("Bluetooth initialized\n");

err = bt_le_adv_start(adv_param, ad, ARRAY_SIZE(ad),
sd, ARRAY_SIZE(sd));
if (err) {
LOG_ERR("Advertising failed to start (err %d)\n", err);
return;
}

LOG_INF("Advertising successfully started\n");

for (;;) {
dk_set_led(RUN_STATUS_LED, (++blink_status) % 2);
k_sleep(K_MSEC(RUN_LED_BLINK_INTERVAL));
}
}

[Sigurd Hellesvik]

Hi, I will look into this case and return with more information tomorrow

Regards,
Sigurd Hellesvik

[Sigurd Hellesvik]

Jerry Easley said:

he following is a program from the BLE tutorial

Which BLE tutorial?

I can search on terms like "nRF52 USB CDC ACM tutorial" and your search engine ignores the quotes and I get over 700 hits.

As an alternative, you can use google with "site". It sometimes returns better results.

To create a sample which might be useful to you, I did the following:

nRF Connect SDK v2.3.0.

Use the Hello World sample as a base.

Copy the app.overlay and prj.conf from Console over CDC ACM UART Sample into Hello World.
Add usb_enable() to hello world.
Add hello world printk into loop

I tested this on a DK, so I think that it should work on the dongle as well:

hello_world_over_cdc_acm.zip

Regards,
Sigurd Hellesvik

[Jerry Easley]

The BLE tutorial, "

Bluetooth Low Energy Fundamentals

" is here: https://academy.nordicsemi.com/topic/blefund-lesson-2-exercise-1/

You can get the example programs here: https://github.com/NordicDeveloperAcademy/bt-fund.git

Each Lesson Exercise comes with two source files a student working copy and a solution copy; I am working with the solution copy.

I am sure the solution you provided will work for me; I haven't had a chance to try it; I'll try it straight away and give you some feedback. Thank you so much for your efforts.

Regards,

Jerry

[Jerry Easley]

Hi Sigurd,

Your example works great! Thank You ever so much!

Regards,

Jerry