Threshold of sensortag(exactly acceleormeter)

Hi,

Yes, default wake up threshold is 0.5g. 

Default value of register = 0000 1000 (0x08)

If you see equation which is on next page,

Threshold steps =  (threshold in g) * 16 

for 0.5G steps = 8. Thus default value = 8. 

Thanks a lot for your reply.

threshold steps = 8 is in Counts unit? please when can i find this value in Sensortag open source, and it is possible to modify it?

2) - It is necessary to calculate Wake Up Delay Time ?

Thank you in advance 

Hi,

You can modify it easily in FW code. 

If you have BLE stack 1.4.0, then hal_acc.c file is driver file for accelerometer. 

You can write corresponding value to register as needed. you can find file at :  

C:\Texas Instruments\BLE_CC254x_140\Components\hal\target\CC2541ST\hal_acc.c

Example driver is not changing value, but register definitions are given at top. You can write to the wake up threshold register and modify it. 

Regarding wake up time calculations, Yes it is necessary to calculate because if your sensor is in sleep mode then when you are reading sample from it, you need to wake up the sensor. You can take reliable reading from sensor after wake up delay time only. 

If your sensor is always on then you don't need to worry about wake up delay. It's not that much critical.

Hi, 

These are all address of registers. ACC_REG_ADDR_TDT_L_THRESH  represents address of threshold register not content.  In short whenever macro contains wors "ADDR" it means it represents address. 

No, there is no function to calculate tilt but you can search an algorithm to calculate tilt and implement on application side. 

Hi, 

So when can i find content of  "ACC_REG_ADDR_TDT_L_THRESH"

Thanks in advance 

Hi,

If you see in accelerometer driver, there is no code for modifying threshold value. 

If you want to read default value use "HalSensorReadReg" API which is available in hal_sensor.c 

function :  bool HalSensorReadReg(uint8 addr, uint8 *pBuf, uint8 nBytes)

you can pass address as "ACC_REG_ADDR_TDT_L_THRESH" , take one buffer of single byte and pass address, and nBytes = 1. 

Thus you can read default value. 

If you want to modify it, you can use "HalSensorWriteReg" function. 

Hi, 

Thanks a lot for your reply.

1) - To read the value of Threshold, I tried to modify addr with "ACC_REG_ADDR_TDT_L_THRESH" like this:

bool HalSensorReadReg(uint8 ACC_REG_ADDR_TDT_L_THRESH , uint8 *pBuf, uint8 nBytes)

{
uint8 i = 0;
nBytes = 1;

/* Send address we're reading from */
if (HalI2CWrite(1,&ACC_REG_ADDR_TDT_L_THRESH ) == 1)
{
/* Now read data */
i = HalI2CRead(nBytes,pBuf);
}

return i == nBytes;
}

After i debug the program which don't give me error; i search for output of this function but i can't find its place. 

2) - In Sensortag, the value of threshold is 0.5? Can i do my work with this value?

Thanks in advance 

Hi, 

You don't need to modify "HalSensorReadReg" function for that. 

Sample code: 

uint8 data_read = 0; 
uint8 no_of_bytes = 1; 
bool status = 0; 

status = HalSensorReadReg(ACC_REG_ADDR_TDT_L_THRESH , &data_read , no_of_bytes);

Now, check that status should return 0 after this function has been called. data_read should contain data of register.

2. Yes, you can do your work with wakeup threshold of 0.5G. (I assume you just want to get data of accelerometr) . 

Hi , 

Thanks very very much. 

Please , it's possible to connect SensorTag to Matlab to view data in real time . I'm using BLE Device Monitor, but it's an application not open source, should i create my own application? If yes, should i use a functions in SensoTag?

Thanks a lot in advance 

Hi,

I am not aware whether it can work with Matlab  or not. 

But you can use android application or make one. 

Here is source code for BLE sensor tag demo app : 

https://github.com/StevenRudenko/BleSensorTag