Only one character is seen when reading a string as a gatt characteristic

RE: Only one character is seen when reading a string as a gatt characteristic

kruenheck — Mon, 10 Nov 2025 14:42:14 GMT

that fixed it, thank you.

RE: Only one character is seen when reading a string as a gatt characteristic

Hung Bui — Mon, 10 Nov 2025 12:01:10 GMT

Hi Keith,

I assume you were using the same read callback implementation showed in the peripheral_lbs or in the academy BLE course ?
I think the issue is that you pass sizeof(*value) as the length of the attribute. In LBS sample it's only one byte boolean either the button is 1 or it's 0.

In your case you will need to pass the actual length of the version string swRev_state. Also make sure you declare the buffer swRev_state as a string/array.

RE: Only one character is seen when reading a string as a gatt characteristic

kruenheck — Fri, 07 Nov 2025 14:54:01 GMT

here is the important pieces:

static ssize_t read_swRev(struct bt_conn *conn, const struct bt_gatt_attr *attr, void *buf, uint16_t len, uint16_t offset)
{
    // get a pointer to software revision which is passed in the BT_GATT_CHARACTERISTIC() and stored in attr->user_data
    const char *value = attr->user_data;

    if (dis_cb.swRev_cb)
    {
        swRev_state = dis_cb.swRev_cb();                
        return bt_gatt_attr_read(conn, attr, buf, len, offset, value, sizeof(*value));         
    }

    return 0;
}


static struct my_dis_cb appDis_callbacks =
{
        .swRev_cb = app_SwRev_cb,
};
 

#define SW_REVISION  
static char *app_SwRev_cb(void)
{
    return "Rev0_04";
}

RE: Only one character is seen when reading a string as a gatt characteristic

Hung Bui — Fri, 07 Nov 2025 13:32:35 GMT

Hi Keith,
What do you have in read_swRev() ? It's where the application supply to the stack what value it should return to the client when a read request is sent.
Can you provide the project here so we can take a look ?