AN36 question

[michurin]

this is quote from AN36> 4.2 Set up

The nRF51822 Evaluation Kit is needed for this application example. However, it is possible to modify the project to also work with the Development Kit. 4.2.1 Setting up the Evaluation board Since the nRF51822 Evaluation Kit has an onboard SEGGER chip, you can connect the Evaluation board through a USB cable and immediately start working on it. 4.2.2 Setting up the application A lot of boilerplate code is needed to get started creating an application and a service, so the first step is to copy code from the SDK:

1. Go to Board\nrf6310\ble\ble_app_template folder.
2. Copy this folder to Board\pca10001\ble\ and rename it to ble_app_lbs.
3. Inside the Arm subfolder of ble_app_lbs change the name of the project files from ble_app_template to ble_app_lbs.

At the same time AN36 has folder code[u][/u] which includes ble_app_lbs.uvproj

Could someone please clarify.

The second question/clarification is where can I find parameters SD110 used on pca10005 and pca10004 for keil?

Thank you.

[michurin]

I'm assuming than when initialization of (ble_gatts_attr_t)attr_char_value.init_len and (ble_gatts_attr_t)attr_char_value.max_len takes place sizeof of the attribute characteristic value should be used: i.e. if my initial value is string

#define MAX_LEN 20
char first[] = "hello world";
char last[] = "good bye cruel world";

During init

attr_char_value.p_value = first;
attr_char_value.init_len = strlen(first);
attr_char_value.max_len = MAX_LEN;

later

attr_char_value.p_value = last;
attr_char_value.init_len = strlen(last);

Am I correct?

[Ole Morten]

There is no use in modifying the attr_char_value after initialization, as it isn't used then. To change the value after init, you have to use sd_ble_gatts_value_set().

However, the way of setting init_len and max_len seems reasonable.

[michurin]

Could you please be a bit more specific about:"There is no use in modifying the attr_char_value after initialization, as it isn't used then."?

If one have a value and a string describing this value how can it be no use in modifying it? I'm confused.

Thank you.

[Ole Morten]

I don't think I fully understand what you mean. Perhaps we could take a few steps back, to make it clear what you try to achieve.

Anyway, what I meant was this: The structure which holds the p_value and init_len fields is the ble_gatts_attr_t struct. This struct is then passed to sd_ble_gatts_characteristic_add(), and whatever value is in at the time of this function call is the value that is used. If you try to modify the value of this structure after having called sd_ble_gatts_characteristic_add(), that will cause no change. This was how I understood your reply here, since you write first "During init" and then "later".

[michurin]

uint32_t sd_ble_gatts_value_set (uint16_t handle, uint16_t offset, uint16_t *const p_len, uint8_t const *const p_value); Is there any problem to update my app value without this method except that I'm guessing the method provides atomic access. Isn't this method just memcpy()?

Thanks

[michurin]

BTW. If my value is a string of variable length how it this length(<=max_len) is handled? Another characteristic? Other means know by both sides? Thanks.