Can't receive bytes sent via ByteArray in nRFConnect App

[morpho]

I created a custom BLE service following this tutorial and I am able to connect to the BLE service and write data to it, but ideally, I want to send character bytes as opposed to just decimal values. 

In the nRFConnect app, seemingly ByteArray is a field to enter character bytes but when I enter a character, on_write is invoked and p_evt_write->len remains 0, and so is p_evt_write->data. 
But when I send in an Unsigned field, I receive the expected data and so does the length.

Also can we not send multiple bytes at once? because otherwise p_evt_write->len would always remain 1 hence no actual use.

Am I using the ByteArray field correctly? 

[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)

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?

[Einar Thorsrud]

Hi,

morpho said:

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)

Can you share your code so that I can see?

morpho said:

Secondly, there's no way for you to send string bytes?

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.

[morpho]

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;
}

[Einar Thorsrud]

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

[morpho]

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