Send data from central device to peripheral device.

[RHOOD]

Hi,

I am attempting to modify the central_hr and peripheral_hr code to send data from the central device to the peripheral and have the peripheral device print out what it has received. So far I have modified the heart-rate characteristic so that it will receive an unsigned integer and when I connect to it via the the nRFConnect app I can send it an integer and it will print it out just fine. However, when I attempt to modify the central_hr to send an unsigned integer via bt_gatt_write() or bt_gatt_write_without_response() it doesn't seem to work. The two devices are connecting fine and the central is receiving the mock heart-rate data but as far as I can tell the peripheral is not receiving anything. Am I missing a step? Do I have to do additional setup to get the central to write data to the peripheral characteristic? I am a little stalled out here and I am not sure I understand the central code very well so any help would be appreciated. The modifications to the peripheral work as intended with the nrfConnect app so I assume the issue is in the central but I don't know what that could be.

I will show some of the relevant code below and I am using a 52840 dev kit as the peripheral and a 5340 dev kit as the central.

Where I am calling bt_gatt_write_without_response() (I have hrs.h included in the central code)

static uint8_t notify_func(struct bt_conn *conn,

               struct bt_gatt_subscribe_params *params,

               const void *data, uint16_t length)

{

    if (!data) {

        printk("[UNSUBSCRIBED]\n");

        params->value_handle = 0U;

        return BT_GATT_ITER_STOP;

    }

    printk("[NOTIFICATION] data %u length %u\n",((uint8_t*)data)[1], length);

    //struct bt_gatt_write_params write_params;

    //bt_hrs_notify(99U);

    static uint8_t datadata = 10;

    bt_gatt_write_without_response(conn, BT_UUID_HRS_MEASUREMENT_VAL, datadata, sizeof(datadata), false);

    printk("Data %u sent\n", datadata);

    return BT_GATT_ITER_CONTINUE;

}

Here is where I edited the characteristic in hrs.c

BT_GATT_SERVICE_DEFINE(hrs_svc,

    BT_GATT_PRIMARY_SERVICE(BT_UUID_HRS),

    BT_GATT_CHARACTERISTIC(BT_UUID_HRS_MEASUREMENT, BT_GATT_CHRC_NOTIFY|BT_GATT_CHRC_WRITE_WITHOUT_RESP,

                   BT_GATT_PERM_WRITE, NULL, print_data, NULL),

    BT_GATT_CCC(hrmc_ccc_cfg_changed,

            HRS_GATT_PERM_DEFAULT),

    BT_GATT_CHARACTERISTIC(BT_UUID_HRS_BODY_SENSOR, BT_GATT_CHRC_READ,

                   HRS_GATT_PERM_DEFAULT & GATT_PERM_READ_MASK,

                   read_blsc, NULL, NULL),

    BT_GATT_CHARACTERISTIC(BT_UUID_HRS_CONTROL_POINT, BT_GATT_CHRC_WRITE,

                   HRS_GATT_PERM_DEFAULT & GATT_PERM_WRITE_MASK,

                   NULL, NULL, NULL),

);

Here is print_data function

static ssize_t print_data(struct bt_conn *conn, const struct bt_gatt_attr *attr, const void *buf,

             uint16_t len, uint16_t offset, uint8_t flags)

{

    LOG_DBG("Attribute write, handle: %u, conn: %p", attr->handle, (void *)conn);

    if (len != 1U) {

        //LOG_DBG("Write led: Incorrect data length");

        return BT_GATT_ERR(BT_ATT_ERR_INVALID_ATTRIBUTE_LEN);

    }

    if (offset != 0) {

        //LOG_DBG("Write led: Incorrect data offset");

        return BT_GATT_ERR(BT_ATT_ERR_INVALID_OFFSET);

    }

    printk("DATA IS: %d", *((uint8_t *)buf));

    return len;

}

[dejans]

Hi,

Where are functions that are shown in your code located in your project?

Where do you call print_data() from, and how?

Best regards,
Dejan

[RHOOD]

Hi.  Hadn't gotten a chance to update this but I managed to get it working by calling "aubacribe_params.value_handle" in bt_gatt_write_without_response in place of BT_UUID_MEASUREMENT_VAL and de-refrencing datadata in bt_gatt_write_without_response. Thank you for your reply!

[dejans]

Hi,

Thank you for the update.

Best regards,
Dejan