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Question about high speed ADC usage

ahmed

Hi,

I need to send an audio signal through BLE connection of nRF51822 module, this signal need to quantized and sampled at rate of minimum 8000 sample/second by ADC, i configured the minimum connection interval to 9 ms but the sampling still very low and far from required, i try to decrease the interval below 9 ms but the connection failed. is there any way to increase the sampling rate?

Thanks for your help in this issue

Regards

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  • 0 
    #define 	BLE_GAP_CP_MIN_CONN_INTVL_MIN   0x0006

    That's in 1.25ms intervals so 7.5ms is the absolute minimum. That's per BTLE spec.

    I don't understand why you refer to increasing 'the sampling rate', doesn't seem like the ADC sampling rate is your problem, it's the BTLE transfer throughput. How are you sending the data, in what sized packets? There's a theoretical maximum of 6 packets per connection interval (I don't recall where that comes from) but it's stated in other questions that many implementations are limited to 4. if you're sending 20 bytes per packet, at 9ms connection interval that's around 8kB/second, if you're only sending one byte per packet, it's about 450 b/second.

    And what's on the other end of this link? Just because you request a minimum connection interval of 7.5ms, doesn't mean the master on the other side lets you have it.

  • 0 in reply to RK

    Dear RK,

    It is 10 bit ADC data sending via UART as a text which mean 4 byte by using UART over Bluetooth ble_nus_string_send, i need 8K sample/second, if the 9 ms is minimum connection time with 4 packets that is mean i just can get a 444 sample/second (1/9ms * 4), are this calculation right ?

    Thanks for your help

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  • 0 in reply to RK

    Dear RK,

    It is 10 bit ADC data sending via UART as a text which mean 4 byte by using UART over Bluetooth ble_nus_string_send, i need 8K sample/second, if the 9 ms is minimum connection time with 4 packets that is mean i just can get a 444 sample/second (1/9ms * 4), are this calculation right ?

    Thanks for your help

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