Can I change the measurement unit on BLE Heart Rate example?

[ndarkness]

Hello,

I am using the BLE_app_hrs_pca example and I was wondering whether or not the unit in which my beat rate is encoded (bpm) can be changed. I mean, I would like to set it to beat per hour, for instance, does this value need to be specified on the cccd_md of the BLE service ? If so how can I do it?

I have been reading Nordic tutorial but it is still not completely clear for me.

Looking into ble_hrs.c I can see that the value is defined on BLE_UUID_BLE_ASSIGN() method, however I cannot find the unit that is sent out. Any hints?

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

char_md.char_props.notify = 1;
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         = &cccd_md;
char_md.p_sccd_md         = NULL;

BLE_UUID_BLE_ASSIGN(ble_uuid, BLE_UUID_HEART_RATE_MEASUREMENT_CHAR);

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

attr_md.read_perm  = p_hrs_init->hrs_hrm_attr_md.read_perm;
attr_md.write_perm = p_hrs_init->hrs_hrm_attr_md.write_perm;
attr_md.vloc       = BLE_GATTS_VLOC_STACK;
attr_md.rd_auth    = 0;
attr_md.wr_auth    = 0;
attr_md.vlen       = 1;

thanks in advance

[Sigurd]

Hi,

The Heart Rate Measurement characteristic (UUID 0x2A37) is predefined by BLE SIG. All centrals that connects to your peripheral will interpret this value as beats per minute when its sees the that the characteristic have that specific UUID. If this does not suit your application, you should instead create your own custom services and characteristics.

Lists of predefined BLE SIG services and characteristics can be found here and here.