BLE Writable Variables

RE: BLE Writable Variables

SteveHx — Tue, 03 Apr 2018 14:35:27 GMT

If I'm reading that correctly, the answer is that it's a bug in nRF Connect, that's not likely to be fixed soon, and there's no workaround. What a way to run a railroad!

RE: BLE Writable Variables

Kenneth — Tue, 03 Apr 2018 13:50:35 GMT

You can check out this case: https://devzone.nordicsemi.com/f/nordic-q-a/31253/is-it-possible-to-display-integer-on-nrf-connect-app

RE: BLE Writable Variables

SteveHx — Thu, 29 Mar 2018 16:28:55 GMT

I now have my example working based on Blinky, and it's much cleaner than being based on CGMS even though the latter is closer to what I'm ultimately trying to accomplish. I have changed the value being reported for a button press to reflect the value I need to report, and have even succeeded at making it a 2-byte value instead of one byte as in the Blinky example code. So far so good. But I need to have the number treated as a 16-bit SFloat type, and displayed accordingly. Here's how I've modified the relevant section of button_char_add to change the type and units, but thus far it's completely ignored.

    char_md.char_props.read   = 1;
    char_md.char_props.notify = 1;
    char_md.p_char_user_desc = (uint8_t *) "Glucose";
    char_md.char_user_desc_max_size = 12;
    char_md.char_user_desc_size = 7;
    char_pf.format = 0x16;   // 16-bit SFLOAT
    char_pf.unit   = 0x27B1; // units of mG per dL
    char_md.p_char_pf         = &char_pf;
    char_md.p_user_desc_md    = NULL;
    char_md.p_cccd_md         = &cccd_md;
    char_md.p_sccd_md         = NULL;

    ble_uuid.type = BLE_UUID_TYPE_BLE; //FIXME p_lbs->uuid_type;
    ble_uuid.uuid = BLE_UUID_CGM_MEASUREMENT;

Also, what's the best way to ensure that all the previously-captured configuration information that shows up in nRF Connect is actually refreshed from my code? I've been tripped up several times by nRF Connect continuing to use old values after I change my code. I'm not sure exactly what steps to take.

RE: BLE Writable Variables

SteveHx — Wed, 28 Mar 2018 15:10:04 GMT

I have been chasing my tail and burning up my client's billable hours for a couple weeks now on this. Is it really too much to ask that there be a simple example of a characteristic that allows me to write a value from a phone into my app and have it call a routine? Based on more decades of embedded development than I really want to admit, there should be a simple table for BLE, with a line for each variable of interest, containing a pointer to an internal variable, the size of that variable, formatting information, flags to allow read or write, and pointers to one or both functions to be called before the value is read and after it is written. I have struggled with the CGMS example and have it displaying a value from my analog hardware in real time, but it was way more of a struggle than it should have been. Could someone PLEASE point me to some example code that actually works, and containing a simple example that I can lift into my code, that will allow me to write a variable from BLE?

RE: BLE Writable Variables

SteveHx — Mon, 26 Mar 2018 21:15:19 GMT

Okay, thanks. I'll have another look at that. I had tried using that but got lost in that unwieldy chain of calls stacked into calls and structs stacked on structs.

RE: BLE Writable Variables

Daniel Wang — Mon, 26 Mar 2018 20:25:59 GMT

The ble_app_blinky example could maybe be helpful. In that example you could write 0 or 1 in nRFConnct on the LED Characteristic (0x1525) to turn the LED off/on.