RE: GATT characteristic value not maintained if initial value is 0

edmcnicholas — Thu, 14 Aug 2025 13:50:55 GMT

Read Before Indicate

Read After

If gSenseVal is 0 in the definition this happens if it is anything else the value is maintained i.e.

static uint8_t gSenseVal = 0xff;

RE: GATT characteristic value not maintained if initial value is 0

edmcnicholas — Thu, 14 Aug 2025 13:48:10 GMT

/*
 *   Copyright (c) 2024 Rogue Solutions LLC
 *   All rights reserved.
 */

#include <errno.h>
#include <zephyr/init.h>
#include <zephyr/sys/__assert.h>
#include <stdbool.h>
#include <zephyr/types.h>

#include <zephyr/bluetooth/bluetooth.h>
#include <zephyr/bluetooth/conn.h>
#include <zephyr/bluetooth/gatt.h>
#include <zephyr/bluetooth/uuid.h>

#include "bleLTECwldm.h"
#include "btLTEC.h"

#include <zephyr/logging/log.h>
LOG_MODULE_REGISTER(bt_wldm, LOG_LEVEL_INF);

/*******************************************************************************
* Defines 
*******************************************************************************/



/*******************************************************************************
* Private Declerations 
*******************************************************************************/
static int wldm_init(void);

static void hit_ccc_cfg_changed(const struct bt_gatt_attr* attr, uint16_t value);

static void indicate_cb(struct bt_conn* conn, struct bt_gatt_indicate_params* params, unsigned char err);

static ssize_t read_hit(struct bt_conn* conn, const struct bt_gatt_attr* attr, void* buf, uint16_t len, uint16_t offset);

static ssize_t read_sense(struct bt_conn* conn, const struct bt_gatt_attr* attr, void* buf, uint16_t len, uint16_t offset);

static ssize_t write_sense(struct bt_conn* conn, const struct bt_gatt_attr* attr, const void* buf, uint16_t len, uint16_t offset,
                           uint8_t flags);

/*******************************************************************************
* Private Variables 
*******************************************************************************/

/* Custom Service Variables */
static struct bt_uuid_128 BT_UUID_MILES       = LTEC_UUID_INIT(MILES_UUID_SERVICE);
static struct bt_uuid_128 BT_UUID_MILES_HIT   = LTEC_UUID_INIT(MILES_UUID_HIT_CHAR);
static struct bt_uuid_128 BT_UUID_MILES_SENSE   = LTEC_UUID_INIT(MILES_UUID_SENSITIVITY_CHAR);

/* Indication parameters for MILES HIT char */
static struct bt_gatt_indicate_params g_hit_char_ind_params = {0};
static volatile bool g_b_is_hit_ind_enabled                 = false;

static struct ble_wldm_event g_miles_event = {
    .u16Pid         = 0,
    .u8BasicCode    = 0,
    .u8AmmoCode     = 0,
    .u8NumWords     = 0,
    .u8DetectorType = 0,
};

static struct wldmSenseWork gSenseWork = {0};

static uint8_t gSenseVal = 0; // Default to 127, which is the max sensitivity.
/***************************************************************************************************************************************
Profile Definition
***************************************************************************************************************************************/

BT_GATT_SERVICE_DEFINE(
    wldm, BT_GATT_PRIMARY_SERVICE(&BT_UUID_MILES.uuid),
    BT_GATT_CHARACTERISTIC(&BT_UUID_MILES_HIT.uuid, BT_GATT_CHRC_READ | BT_GATT_CHRC_INDICATE,
                           BT_GATT_PERM_READ, read_hit, NULL, &g_miles_event), 
    BT_GATT_CCC(hit_ccc_cfg_changed, BT_GATT_PERM_READ | BT_GATT_PERM_WRITE),
    BT_GATT_CHARACTERISTIC(&BT_UUID_MILES_SENSE.uuid, BT_GATT_CHRC_READ | BT_GATT_CHRC_WRITE ,
                                              BT_GATT_PERM_READ | BT_GATT_PERM_WRITE, read_sense, write_sense, NULL));

/*******************************************************************************
* Public Functions 
*******************************************************************************/

int bt_wldm_report_hit(uint16_t uPid, uint8_t u8BasicCode, uint8_t u8AmmoCode, uint8_t u8NumWords, uint8_t u8DetectorType)
{
    int rc;
    g_miles_event.u16Pid         = uPid;
    g_miles_event.u8BasicCode    = u8BasicCode;
    g_miles_event.u8AmmoCode     = u8AmmoCode;
    g_miles_event.u8NumWords     = u8NumWords;
    g_miles_event.u8DetectorType = u8DetectorType;


    // Don't try to indicate if indications haven't been enabled.
    if (!g_b_is_hit_ind_enabled)
    {
        LOG_DBG("Not indicating because indications are not enabled");
        return 0;
    }

    // ind_params.attr MUST be set to the GATT service attribute if the characteristic attribute
    // being indicated has a shared UUID (e.g. LTEC_PID_CHAR_UUID). This tells the BT stack where to
    // start looking for the characteristic attribute with the uuid ind_params.uuid value.
    g_hit_char_ind_params.attr = attr_wldm;
    g_hit_char_ind_params.uuid = &BT_UUID_MILES_HIT;
    g_hit_char_ind_params.func = indicate_cb;
    g_hit_char_ind_params.data = &g_miles_event;
    g_hit_char_ind_params.len  = sizeof(g_miles_event);

    
    rc = bt_gatt_indicate(NULL, &g_hit_char_ind_params);
    if (rc)
    {
        LOG_WRN("Hit Indicate failed: %d", rc);
    }

    return rc == -ENOTCONN ? 0 : rc;

	// return rc == -ENOTCONN ? 0 : rc;
}

int bt_wldm_SetSensitivtyHandler(k_work_handler_t handler)
{
    k_work_init(&gSenseWork.work, handler);
}


int bt_wldm_SetSensitivty(uint8_t uLvl)
{
    gSenseVal = uLvl;
}

/*******************************************************************************
* Private Functions  
*******************************************************************************/

static int wldm_init(void)
{
    LOG_DBG("BT WLDM Init");
    gSenseVal =0;
	return 0;
}

static void hit_ccc_cfg_changed(const struct bt_gatt_attr* attr, uint16_t value)
{
    ARG_UNUSED(attr);

    bool ind_enabled = (value == BT_GATT_CCC_INDICATE);

    g_b_is_hit_ind_enabled = ind_enabled;

    LOG_INF("MILES Hit Indication %s", ind_enabled ? "enabled" : "disabled");
}

static void indicate_cb(struct bt_conn* conn, struct bt_gatt_indicate_params* params, unsigned char err)
{
    LOG_INF("MILES Hit Indication %s", err != 0U ? "fail" : "success");
    // todo handle
}

/* BLE Read Functions */

static ssize_t read_hit(struct bt_conn* conn, const struct bt_gatt_attr* attr, void* buf, uint16_t len, uint16_t offset)
{
    return bt_gatt_attr_read(conn, attr, buf, len, offset, &g_miles_event, sizeof(g_miles_event));
}

static ssize_t read_sense(struct bt_conn* conn, const struct bt_gatt_attr* attr, void* buf, uint16_t len, uint16_t offset)
{
    // uint8_t status = gSenseVal;

    return bt_gatt_attr_read(conn, attr, buf, len, offset, &gSenseVal, sizeof(gSenseVal));
}

/* BLE Write Functions */

static ssize_t write_sense(struct bt_conn* conn, const struct bt_gatt_attr* attr, const void* buf, uint16_t len, uint16_t offset,
                           uint8_t flags)
{
    struct net_buf_simple data;

    if (flags & BT_GATT_WRITE_FLAG_PREPARE)
    {
        return 0;
    }

    if (offset + len > sizeof(gSenseVal))
    {
        return BT_GATT_ERR(BT_ATT_ERR_INVALID_OFFSET);
    }

    net_buf_simple_init_with_data(&data, (void *)buf, len);
	gSenseVal = net_buf_simple_pull_u8(&data);

    LOG_INF("Sense Write %x", gSenseVal);
    /* Submit Reset Work */
    if(gSenseWork.work.handler != 0)
    {
        gSenseWork.uLevel = gSenseVal;
        k_work_submit(&gSenseWork);
    }
    return len;
}


SYS_INIT(wldm_init, APPLICATION, CONFIG_APPLICATION_INIT_PRIORITY);

RE: GATT characteristic value not maintained if initial value is 0

edmcnicholas — Thu, 14 Aug 2025 12:38:09 GMT

I have another characteristic that I notify in. This happens to a second profile whenever I notify.

RE: GATT characteristic value not maintained if initial value is 0

Sigurd — Thu, 14 Aug 2025 12:35:44 GMT

Hi!

[quote user=""]whenever there is a BLE update the value goes to 0xff. [/quote]

What do you mean by BLE update?

Also, could you post some more code that shows what you are doing with this variable ?

RE: GATT characteristic value not maintained if initial value is 0

edmcnicholas — Thu, 14 Aug 2025 00:46:39 GMT

New fun fact it only happens to 8 bit variables or structures