Can't receive bytes sent via ByteArray in nRFConnect App

RE: Can't receive bytes sent via ByteArray in nRFConnect App

Einar Thorsrud — Mon, 04 Oct 2021 07:33:53 GMT

The max_len field indicates the maximum length, so it is up to. You can always write a smaller value, the point is that it cannot be larger than the specified maximum.

(I see now that my statement "The max_len here dictates the maximum length of the value, neither more or less" can be confusing. The point was that max_len does not do anything other than limiting the maximum length. So, it does not say anything about number of writes before you get an interrupt or similar as you asked about before I answered that).

RE: Can't receive bytes sent via ByteArray in nRFConnect App

morpho — Sat, 02 Oct 2021 06:05:23 GMT

is it UP TO or neither more nor less which you indicated earlier? Unless I'm misinterpreting

RE: Can't receive bytes sent via ByteArray in nRFConnect App

Einar Thorsrud — Fri, 01 Oct 2021 08:59:05 GMT

This looks OK for writing up to 5 bytes. Does it not work if you use ByteArray with hex or UTF8 with characters?

RE: Can't receive bytes sent via ByteArray in nRFConnect App

morpho — Thu, 30 Sep 2021 20:46:27 GMT

static uint32_t custom_value_char_add(BleCust * p_cus, const BleCustInit_t * p_cus_init)
{
    uint32_t            err_code;
    ble_gatts_char_md_t char_md;
    ble_gatts_attr_md_t cccd_md;
    ble_gatts_attr_t    attr_char_value;
    ble_uuid_t          ble_uuid;
    ble_gatts_attr_md_t attr_md;

    memset(&char_md, 0, sizeof(char_md));

    char_md.char_props.read   = 1;
    char_md.char_props.write  = 1;
    char_md.char_props.notify = 0; 
    char_md.p_char_user_desc  = NULL;
    char_md.p_char_pf         = NULL;
    char_md.p_user_desc_md    = NULL;
    char_md.p_cccd_md         = NULL; 
    char_md.p_sccd_md         = NULL;
		
    memset(&attr_md, 0, sizeof(attr_md));

    attr_md.read_perm  = p_cus_init->customCharAttr.read_perm;
    attr_md.write_perm = p_cus_init->customCharAttr.write_perm;
    attr_md.vloc       = BLE_GATTS_VLOC_STACK;
    attr_md.rd_auth    = 0;
    attr_md.wr_auth    = 0;
    attr_md.vlen       = 0;

    ble_uuid.type = p_cus->uuidType;
    ble_uuid.uuid = CUSTOM_VALUE_CHAR_UUID;

    memset(&attr_char_value, 0, sizeof(attr_char_value));

    attr_char_value.p_uuid    = &ble_uuid;
    attr_char_value.p_attr_md = &attr_md;
    attr_char_value.init_len  = sizeof(uint8_t);
    attr_char_value.init_offs = 0;
    attr_char_value.max_len   = sizeof(uint8_t) * 5;

    err_code = sd_ble_gatts_characteristic_add(p_cus->serviceHandle, &char_md,
                                               &attr_char_value,
                                               &p_cus->customValueHandle);
    if (err_code != NRF_SUCCESS)
    {
        return err_code;
    }

    return NRF_SUCCESS;
}

RE: Can't receive bytes sent via ByteArray in nRFConnect App

Einar Thorsrud — Thu, 30 Sep 2021 07:28:32 GMT

Hi,

[quote user="morpho"]Okay, so I tried again and despite having max_len at sizeof(uint8_t) * 5, I can send/receive < 5 bytes. Do you see why would that be? (p_evt_write->len < 5)[/quote]

Can you share your code so that I can see?

[quote user="morpho"]Secondly, there's no way for you to send string bytes?[/quote]

When you have selected ByteArray, then yes. If you select UTF8, you can enter a string and it will be automatically converted to ASCII for you.

RE: Can't receive bytes sent via ByteArray in nRFConnect App

morpho — Thu, 30 Sep 2021 03:13:22 GMT

Okay, so I tried again and despite having max_len at sizeof(uint8_t) * 5, I can send/receive < 5 bytes. Do you see why would that be? (p_evt_write->len < 5)

Secondly, there's no way for you to send string bytes? Would you have to consult to the ASCII table to make sure you're sending the expected chars?

RE: Can't receive bytes sent via ByteArray in nRFConnect App

Einar Thorsrud — Wed, 29 Sep 2021 10:51:37 GMT

Hi,

[quote user="morpho"]I set the max_len to 5 * sizeof(uint8_t), which means I should only be able to send 5 bytes assuming uint8_t is a byte, yes?[/quote]

Yes.

[quote user="morpho"]This video is with max_len sizeof(uint8_t) * 50; (just randomly put in a number)[/quote]

I do not see in the video which characteristic you try to write to. Is it the correct one? Also, with byte array you should use hex characters, so not for instance "Hello" as you use.

RE: Can't receive bytes sent via ByteArray in nRFConnect App

morpho — Wed, 29 Sep 2021 06:13:20 GMT

alright I am still not super clear on max_len and how it's working as my experience with the app has been a bit different. I set the max_len to 5 * sizeof(uint8_t), which means I should only be able to send 5 bytes assuming uint8_t is a byte, yes? when I do so, the app doesn't allow me to send.

This video is with max_len sizeof(uint8_t) * 50; (just randomly put in a number)

devzone.nordicsemi.com/.../RPReplay_5F00_Final1632895423.MP4

RE: Can't receive bytes sent via ByteArray in nRFConnect App

Einar Thorsrud — Tue, 28 Sep 2021 10:34:41 GMT

The max_len here dictates the maximum length of the value, neither more or less. So it is not possible to send more than 1 byte at a time with this configuration. If you want to send data that is larger than 1 byte, you must increase the max_len.

Regarding the Rx characteristic I cannot see much from this video. Is there an error on the nRF side? For instance detected by an APP_ERROR_CHECK()? Have you debugged to check?

RE: Can't receive bytes sent via ByteArray in nRFConnect App

morpho — Tue, 28 Sep 2021 05:00:02 GMT

max_len indicates the max number of bytes that could be sent before the application starts processing/interrupt is triggered then? because currently, every byte I send, on_write is invoked through the ble event handler call.

Also now the RX characteristics button doesn't seem to recognize the tap to bring up the options for the data. do you see what's happening now?

devzone.nordicsemi.com/.../RPReplay_5F00_Final1632804981.MP4

RE: Can't receive bytes sent via ByteArray in nRFConnect App

Einar Thorsrud — Mon, 27 Sep 2021 18:33:10 GMT

Hi,

Can you say more about the characteristic you write to? What is the maximum length? I ask because referring to this snippet from the tutorial, the max length is set to sizeof(uint8_t), which is 1:

    /* This code belongs in custom_value_char_add() in ble_cus.c*/

    memset(&attr_char_value, 0, sizeof(attr_char_value));

    attr_char_value.p_uuid    = &ble_uuid;
    attr_char_value.p_attr_md = &attr_md;
    attr_char_value.init_len  = sizeof(uint8_t);
    attr_char_value.init_offs = 0;
    attr_char_value.max_len   = sizeof(uint8_t);

If you want to write more than one byte at a time, you must set a higher value for max_len.