Data Logger: Higher sampling rate (10KHz)
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15. 7. 6 오전 11:21
Dear All,
Thanks for providing data logger demo.
In Accelerometer (bma280), maximum sampling rate is 1000Hz but I want to sample at 10KHz to acquire more accurate data. Kindly give your advise.

Thanks and Regards
Siva 
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Data Logger: Higher sampling rate (10KHz)
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15. 7. 7 오전 3:17 as a reply to Sivaprakash Sivamani.
Hi Siva,

if you check out the Datasheet for the BMA280 here, you'll see that the Bandwith of the BMA280 is way lower than 10KHZ, therefore I would say it's not possible to set a 10KHz sampling rate. 
The 1000Hz limited is enforced as a "soft" software limited.

- Florian
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Data Logger: Higher sampling rate (10KHz)
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15. 7. 8 오전 7:56 as a reply to Florian Harr.
Hi Florian,
Thanks for your kind reply.


Regards
Siva
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Data Logger: Higher sampling rate (10KHz)
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15. 7. 14 오전 10:54 as a reply to Sivaprakash Sivamani.
Hi Florian,
In BMA280, the sampling rate does not goes beyond 500Hz while verifying in scope (upto 500Hz its working properly) ,even though the maximum sampling rate is specified 1000Hz. Kindly advice me.

Regards
Siva 
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Data Logger: Higher sampling rate (10KHz)
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15. 7. 14 오후 1:19 as a reply to Sivaprakash Sivamani.
Hi Siva,

as the DataLogger Demo is a bit tricky sometimes and doesn't read all values as set, can you confirm that the DataLogger Demo successfully read your set sampling rate and it's definitely not set to 500Hz by default?
Also, I assume for getting a high sampling rate, you've deactivated all other sensors?

Regards,
Florian
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Data Logger: Higher sampling rate (10KHz)
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15. 7. 14 오후 1:41 as a reply to Florian Harr.
Hi Florian,
Yes, I tested all range of values from 1Hz to 500Hz and it reads successfully, but anything more than 500Hz is sealed to 2ms in scope. For example for 1000Hz its displaying data for 2ms (but it should display data for every 1ms). Also disabled all other sensors except BMA380.
For testing I used PA1 as a GPIO pin connected to scope
if (valuesToWrite) {
flag = 1;
if (flag == 1)
{
GPIO->P[ gpioPortA].DOUTSET = 1 << 1;
OS_taskDelay(1);
GPIO->P[ gpioPortA].DOUTCLR = 1 << 1;
flag = 0;
}
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Data Logger: Higher sampling rate (10KHz)
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15. 7. 14 오후 3:05 as a reply to Sivaprakash Sivamani.
If you check the source code, especially the file BMA_280_cc.c, you'll find the following part:
        if (strcmp(bma280_bw, "7.81") == 0) {
            bma280bw = ACCELEROMETER_BANDWIDTH_7_81HZ;
        } else if (strcmp(bma280_bw, "15.63") == 0) {
            bma280bw = ACCELEROMETER_BANDWIDTH_15_63HZ;
        } else if (strcmp(bma280_bw, "31.25") == 0) {
            bma280bw = ACCELEROMETER_BANDWIDTH_31_25HZ;
        } else if (strcmp(bma280_bw, "62.5") == 0) {
            bma280bw = ACCELEROMETER_BANDWIDTH_62_50HZ;
        }
        if (strcmp(bma280_bw, "125") == 0) {
            bma280bw = ACCELEROMETER_BANDWIDTH_125HZ;
        }
        if (strcmp(bma280_bw, "250") == 0) {
            bma280bw = ACCELEROMETER_BANDWIDTH_250HZ;
        }
        if (strcmp(bma280_bw, "500") == 0) {
            bma280bw = ACCELEROMETER_BANDWIDTH_500HZ;
}
Which indicates that the Bandwith for the BMA280 is limited to 500Hz. I believe this is done as the sensors on the XDK have a split bandwith among each other, that's why I asked if you have other Sensors activated.

I will check back with our engineers on this, to confirm if my understanding is correct.

- Florian
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Data Logger: Higher sampling rate (10KHz)
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15. 8. 7 오후 5:34 as a reply to Florian Harr.
Hey Sivaprakash Sivamani,

I need to apologize. I found out that the information posted on July 14 was incorrect and doesn't give a reason for the "limitation".

If you take a look at the top of the logger.ini, depending on your version of the data logger, you'll find a notice taht says:

; Important note: The shortest saving time on the SD-Card from the Sensor is 2ms per Sensor. 
; So if you use all 6 sensors, config. all of them to 1kHz (1ms), it will save each sensor data only every 12ms. 
; Reason is the slow I⊃2;C bus connection, where the Sensors are connected. 
; The Sensors are able to sample every 1ms (1kHz), but the request and getting the data from each sensor takes 2ms. 
; 1kHz could maybe be realized through a SPI implementation. 
; Savingtime = 2ms * Sensor (IC)


As 2ms equals 500Hz and your maximum sampling rate is limited by the writing speed between the I2C and your SD card, the sensors max sampling rate is 500Hz.

- Florian

Edit: 
The max rate per sensor will go down the more sensors you activate. See Quote above.

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Data Logger: Higher sampling rate (10KHz)
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15. 8. 13 오전 10:31 as a reply to Florian Harr.
Hi Florian,
Thanks for your information provided, now I am going to interface BMA 280 via XDK Gateway to external I2C pins so that the size of XDK can be reduced while mounting. In case if I got struck at anypoint will get your advise. Thank you in advance. :)


Regards
Siva
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