sd_ble_gatts_value_get returns 0 first time

[Cusko]

I always read 0 first time I call sd_ble_gatts_value_get(), the second time and forward I read correct value. Even if I call sd_ble_gatts_value_get() twice in a row the first time after reset it returns 0 and second time correct value. But I get the correct length even the first time. p_value is set like:

uint8_t value_test[5];
ble_gatts_value_t test; 
test.p_value = value_test;

This happens even if I call sd_ble_gatts_value_get() 5 min after reset. And in the meantime I can write and read the char value with other device with no problem.

[Hung Bui]

Hi Cusko,

Could you update your code, or send your project here ? It's not normal that you have to call sd_ble_gatts_value_get() twice to get the value.

[Cusko]

lucka_service.h

lucka_service.c

In attachment is file where I use this function. Line 67 in Lucka_service.c. And I noticed another thing. If I use sd_ble_gatts_value_set() before I call sd_ble_gatts_value_get() with the same p_value, I also get correct value. I cannot upload the whole project because is to big. Maybe with email or something.

[Hung Bui]

Hi Cusko,

You mentioned "first time after reset it returns 0" isn't it normal that the initial value after reset of each character is zero (char_State, char_Time) ?

Or you want to say that inside on_write() on the first time you write to p_lus->char_handles_freq.value_handle when you read back the value is 0 ? Have you tried to compare p_ble_evt->evt.gatts_evt.params.write.data[0] with what you get when you call sd_ble_gatts_value_get() ?

Have you checked the return err_code of sd_ble_gatts_value_get() ? if it's nRF_SUCCESS or not ?

[Cusko]

After reset I set the initial value when I initialize the service.

attr_char_value.p_value = &Laser_Freq;

And the initial values are already set before I call service init. As I already said, if I read the char value with another bluetooth device I get the correct value even after reset and before I write this char with another device. The err_code is NRF_SUCCESS. And I do check p_ble_evt->evt.gatts_evt.params.write.data[0] and it is correct value.

[Hung Bui]

@Cusko: have you made sure you set correct .len in lus_char when you call sd_ble_gatts_value_get() ? If you leave it as 0 , the value returned will be 0.

If you still have trouble, please send me a simplified project where you simply read the value after you init the service (don't advertise or anything else).