Sending string data over NUS

RE: Sending string data over NUS

hmolesworth — Sat, 01 Dec 2018 02:06:11 GMT

A few hints you might consider:

sizeof(SomeString) for ascii data transmission is bad, use instead strlen(SomeString). The former includes all the crap on the stack after useful data when used with printf etc and might work but is not reliable. The second attempts to transmit only the ascii data you put in the string

sprintf() is unsafe, use instead snprintf()

"\r" may not be the same as '\r" or snprintf( ... "..\r"); be safe, use snprintf()

Here is an example which might be useful; Central is showing additional information and it works with the Nordic Uart service you are using

static void ReportVersion(void)
{
    char     InfoPacket[120];
    const uint16_t sdMajor  =  SD_VERSION / 1000000;
    const uint16_t sdMinor  = (SD_VERSION - (sdMajor*1000000)) / 1000;
    const uint16_t sdBugfix = (SD_VERSION - ((sdMajor*1000000) + (sdMinor*1000)));
    ble_version_t sdVersion = {0,0,0};
    ble_version_t *p_version = &sdVersion;
    // Get actual installed SoftDevice version (may be different from header file)
    sd_ble_version_get(p_version);

    // Sign on
    // "Central (66906325295D586C) SD Ver. [5.1.0] [59 A5 9]"
    snprintf(InfoPacket, sizeof(InfoPacket), "Central (%08X%08X) SD Ver. [%u.%u.%u] [%X %X %X]\r",
                         NRF_FICR->DEVICEID[1], NRF_FICR->DEVICEID[0], sdMajor, sdMinor, sdBugfix,
                         p_version->company_id, p_version->subversion_number, p_version->version_number);
    SendViaHardwareUart(InfoPacket);
}

Here is a typical uart function expected by the code above

void SendViaHardwareUart(char * InfoPacket)
{
   uint32_t err_code;
   uint32_t txIndex;

   txIndex = strlen(InfoPacket);
   for (uint32_t i = 0; i < txIndex; i++)
   {
      do
      {
         err_code = app_uart_put(InfoPacket[i]);
      } while (err_code == NRF_ERROR_BUSY) ;
   }
   if (InfoPacket[txIndex-1] == '\r')
   {
      while (app_uart_put('\n') == NRF_ERROR_BUSY) ;
   }
}

RE: Sending string data over NUS

howard n2wx — Sat, 01 Dec 2018 00:18:03 GMT

Can you contact me at my hginfla@gmail.com address please?

RE: Sending string data over NUS

Catytu — Wed, 28 Nov 2018 12:37:51 GMT

After moving around some things I found this:

1. Sending the string with a "\n" at the end is the thing preventing the central from printing anything and causing the ERROR 7 in the peripheral's log.

2. Sending "01234567891123456789\r" the central receives the data but only prints a blank space.

3. Seding simply "01234567891123456789" prints "01234" when I try the printing function in the central (posted on the original question) and it prints "01234▒" when I simply printf(p_data)

4. Sending a longer string also results in the central receiving the tx notification but not printing anything.

RE: Sending string data over NUS

howard n2wx — Mon, 26 Nov 2018 20:06:56 GMT

Can you find the call that's throwing the NRF_ERROR_INVALID_PARAM fault? Is it the call to ble_nus_data_send?

RE: Sending string data over NUS

Catytu — Mon, 26 Nov 2018 18:30:09 GMT

I am getting an error message. This is what the log is showing me:

0> <info> app: Connected
0> <info> app: Data len is set to 0x3D(61)
0> <error> app: ERROR 7 [NRF_ERROR_INVALID_PARAM]

RE: Sending string data over NUS

howard n2wx — Mon, 26 Nov 2018 18:21:01 GMT

Now that is odd. Over on the peripheral side, is the return value to ble_nus_data_send() zero (NRF_SUCCESS) or are you getting an error message?

Instrumenting is just a fancy description for logging around suspect bits of code.

RE: Sending string data over NUS

Catytu — Mon, 26 Nov 2018 18:15:20 GMT

When I change the dummy to what you said it doesn't print anything... that is odd.

I'm not sure what you mean by instrumenting the ble_nus_c_evt_handler(). Sorry, I'm rather new to programming in C.

RE: Sending string data over NUS

howard n2wx — Mon, 26 Nov 2018 17:55:57 GMT

You're welcome!

Doesn't it seem like the CR/LF characters are acting as backspaces? What happens if you stretch dummy out to

dummy[] = "012345678911234567892123456789\r\n"; for a 42character long message,

does that truncate the last two characters also or do you only get "01234567" ?

(It may help to instrument ble_nus_c_evt_handler() at the ...TX_EVT, perhaps log the string and its length or set a breakpoint and check out the event fields. Does that make sense?)

RE: Sending string data over NUS

Catytu — Mon, 26 Nov 2018 17:15:27 GMT

That fixed it!

However, even when trying to send a small string like this:

    char dummy[] = "dummy data\r\n"; 

    // Enter main loop.
    for (;;)
    {
        uint32_t       err_code;
        printf(dummy);

        do
        {
          err_code = ble_nus_string_send(&m_nus, &dummy, sizeof(dummy));
          if ( (err_code != NRF_ERROR_INVALID_STATE) && (err_code != NRF_ERROR_BUSY) )
          {
            APP_ERROR_CHECK(err_code);
          }
        } while (err_code == NRF_ERROR_BUSY);
    }

The central only prints "dummy da" repeatedly. I thought that changing the MTU size would solve that. Could you help me?

Thank you for all your time and patience

RE: Sending string data over NUS

howard n2wx — Mon, 26 Nov 2018 16:23:59 GMT

Maybe BLE_GATT_ATT_MTU_DEFAULT in ble_gatt.h is it? I left it at the default 23 and use 247 byte packets. Please also check to see if you're throwing any error messages to the log

RE: Sending string data over NUS

Catytu — Mon, 26 Nov 2018 16:15:38 GMT

I changed NRF_SDH_BLE_GATT_MAX_MTU_SIZE in the sdk_config.h and BLE_GATT_ATT_MTU_DEFAULT in the ble_gatt.h

RE: Sending string data over NUS

howard n2wx — Mon, 26 Nov 2018 16:12:05 GMT

[quote userid="74182" url="~/f/nordic-q-a/40866/sending-string-data-over-nus/159085"]I fixed it! To be honest I'm not sure what I did to make it work. [/quote]

Congratulations! I knew you were close

[quote userid="74182" url="~/f/nordic-q-a/40866/sending-string-data-over-nus/159085"] just have one more question regarding this: when I try to change the default GATT MTU length higher than 64 bytes the boards stop working completely. Does this mean my boards don't support large MTU negotiation?[/quote]

No, it doesn't mean that, your 52832s and s132 v6.x (maybe older ones too) absolutely support large MTU negotiation and it works perfectly. Did you change NRF_SDH_BLE_GATT_MAX_MTU_SIZE in sdk_config.h?

RE: Sending string data over NUS

Catytu — Mon, 26 Nov 2018 16:02:25 GMT

I fixed it! To be honest I'm not sure what I did to make it work.

I just have one more question regarding this: when I try to change the default GATT MTU length higher than 64 bytes the boards stop working completely. Does this mean my boards don't support large MTU negotiation?

RE: Sending string data over NUS

Catytu — Sun, 25 Nov 2018 23:46:11 GMT

Thank you kindly for all your help!

RE: Sending string data over NUS

howard n2wx — Sun, 25 Nov 2018 22:37:46 GMT

I'm stumped and would need your code to figure out what's wrong, and that's not appropriate (we hardly know each other! :-)

Hopefully others with better ideas than I have will chime in. FWIW it sounds like you're very close. Final tips would be to make sure there's nothing untoward in the peripheral side's logs (but you have good results with nrf connect......)

RE: Sending string data over NUS

Catytu — Sun, 25 Nov 2018 15:40:38 GMT

Data packets are indeed being received by nrf connect. I can see them when I click notify.

The boards automatically connect when I turn on the peripheral and stay connected. I increased the MTU in both to 100. Baudrate in both is 57600.

I am using the examples/ble_central/ble_app_uart_c.

When they connect it is turning on the tx_notifs, it prints "connected" and "disconnected" no problem but "data recieved" is never printed and no data is being printed either. Here is my ble_nus_c_evt_handler in case it helps:

switch (p_ble_nus_evt->evt_type)
    {
        case BLE_NUS_C_EVT_DISCOVERY_COMPLETE:
            NRF_LOG_INFO("Discovery complete.");
            err_code = ble_nus_c_handles_assign(p_ble_nus_c, p_ble_nus_evt->conn_handle, &p_ble_nus_evt->handles);
            APP_ERROR_CHECK(err_code);

            err_code = ble_nus_c_tx_notif_enable(p_ble_nus_c);
            APP_ERROR_CHECK(err_code);
            NRF_LOG_INFO("Connected to device with Nordic UART Service.");
            printf("Connected\r\n");
            break;

        case BLE_NUS_C_EVT_NUS_TX_EVT:
            printf("Data received\r\n");
            ble_nus_chars_received_uart_print(p_ble_nus_evt->p_data, p_ble_nus_evt->data_len);
            break;

        case BLE_NUS_C_EVT_DISCONNECTED:
            NRF_LOG_INFO("Disconnected.");
            printf("Disconnected\r\n");
            scan_start();
            break;
    }

RE: Sending string data over NUS

howard n2wx — Sat, 24 Nov 2018 23:48:07 GMT

I understand. The point of the nrf connection is to get the sensor side working Is it working? With nrfconnect are you seeing the data from your sensor-connected peripheral after clicking notify?

If you're not seeing your sensor's data with the nrf connect PC app then I think you need to start at the peripheral. Log what's going on between the sensor's uart and the example/ble_peripheral/ble_app_uart main.c's call to ble_nus_data_send().

If you are seeing your sensor data then your central running something like examples/ble_central/ble_app_uart_c can almost drop-in and replace the PC. You could set up the central to scan for and autoconnect to your peripheral. Then you'll turn tx_notifs on from the central, enlarge the MTU (see this thread devzone.nordicsemi.com/.../158918, and the example's ble_nus_chars_received_uart_print() will emit the sensor data on the pin defined for SER_APP_TX_PIN .

3500 bytes every second is very do-able.

RE: Sending string data over NUS

Catytu — Sat, 24 Nov 2018 22:50:00 GMT

Thanks! Its quite clear now. Sadly, what I'm trying to transmit over BLE is sensor data, and I need a continuous stream of data that I can accumulate. For example, if I send the data over UART to PuTTY I can copy all the data I send over long periods of time for processing. I'm afraid I can't do that with the method you showed me, that's why I'm trying to send it on BLE NUS packets to another board that are then sent over UART to PuTTY in order to accumulate all that data. I need to send about 70 bytes every 20 ms.
Could you help me solve my initial question or could you propose another method?

RE: Sending string data over NUS

howard n2wx — Sat, 24 Nov 2018 22:26:03 GMT

I'll try. My project uses different UUIDs but mostly unmolested NUS inside.

This screencap shows the button on you need to select to turn notifications on:

The periph won't send anything until you turn notifications on that way.

If successful you'll be rewarded with soemthing like this:

And the data will refresh as often as received until you toggle notifications off.

RE: Sending string data over NUS

Catytu — Sat, 24 Nov 2018 22:17:30 GMT

I tried, and they do make a connection. Could you help me and give me a hint as to how I can view the continuous stream of data arriving over BLE on the nrf connect on pc?

RE: Sending string data over NUS

howard n2wx — Sat, 24 Nov 2018 22:10:27 GMT

Have you tried replacing one end of the link (the central would be easiest) with the nrf connect android app or the nrf go PC application? Divide and conquer...

[quote userid="74182" url="~/f/nordic-q-a/40866/sending-string-data-over-nus"] From what I know, the central enters ble_nus_c_evt_handler to establish connection but the NUS_TX_EVT is not being called.[/quote]

The examples do a good job of logging. It'll help reduce uncertainty and forum members will have more to go on in the way of assistance.