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Thread: SNR / SQI info in /proc/ati

  1. #1
    Join Date
    Mar 2003
    Posts
    176

    SNR / SQI info in /proc/ati

    hi there,

    I'm noodling around with being able to remotely monitor signal quality on my S3.

    the output of 'cat /proc/ati' looks like:

    Code:
    Network Interface Module (NIM) 0
    ==================================================
    Demod type:        T314
    Demod I2C address: 0x14
    Tuner type:        Samsung (TDA6651)
    
    FAT (Inband) Tuner
       Signal Lock:         Yes
       Tuned Frequency:     831000000Hz (Center-band)
       Modulation:          256QAM
       RF Source:           Cable
       SNR (SQI):           35dB (0x47 0xf5)
       RS Uncorrectable:    0
       RS Correctable:      0
    
    FDC (Out-of-band) Tuner
       Signal Lock:         Yes
       Frequency:           75250000Hz
       Modulation:          QPSK
       Symbol Rate:         1024
       Inversion:           OFF
       SNR factor:          8257521
       RS Uncorrectable:    0
       RS Correctable:      0
    
    Network Interface Module (NIM) 1
    ==================================================
    Demod type:        T314
    Demod I2C address: 0x18
    Tuner type:        Samsung (TDA6651)
    
    FAT (Inband) Tuner
       Signal Lock:         Yes
       Tuned Frequency:     765000000Hz (Center-band)
       Modulation:          256QAM
       RF Source:           Cable
       SNR (SQI):           36dB (0x48 0x62)
       RS Uncorrectable:    0
       RS Correctable:      0
    
    FDC (Out-of-band) Tuner
       Signal Lock:         Yes
       Frequency:           75250000Hz
       Modulation:          QPSK
       Symbol Rate:         1024
       Inversion:           OFF
       SNR factor:          7383941
       RS Uncorrectable:    0
       RS Correctable:      0
    
    FAT 0: LOCK=1 HZ=831000000 MOD=256QAM SRC=0 SNR=36 UE=0 CE=0
    FDC 0: LOCK=1 HZ=75250000 MOD=QPSK RATE=1024 INV=0
    FAT 1: LOCK=1 HZ=765000000 MOD=256QAM SRC=0 SNR=36 UE=0 CE=0
    FDC 1: LOCK=1 HZ=75250000 MOD=QPSK RATE=1024 INV=0
    the "SQI" measurements are sorta interesting. If you look at those values over a short period of time you get (for the first tuner, here):

    Code:
       SNR (SQI):           36dB (0x48 0x96)
       SNR (SQI):           36dB (0x48 0x71)
       SNR (SQI):           36dB (0x48 0x60)
       SNR (SQI):           36dB (0x48 0xac)
       SNR (SQI):           36dB (0x48 0x5)
       SNR (SQI):           36dB (0x48 0xf9)
       SNR (SQI):           36dB (0x48 0x34)
       SNR (SQI):           36dB (0x48 0xd3)
       SNR (SQI):           36dB (0x49 0x2f)
       SNR (SQI):           36dB (0x48 0x8e)
       SNR (SQI):           36dB (0x49 0xc)
       SNR (SQI):           36dB (0x49 0x1c)
       SNR (SQI):           36dB (0x48 0xe4)
       SNR (SQI):           36dB (0x48 0xb1)
       SNR (SQI):           36dB (0x49 0x32)
       SNR (SQI):           36dB (0x49 0x32)
       SNR (SQI):           36dB (0x49 0x7d)
       SNR (SQI):           36dB (0x49 0x46)
       SNR (SQI):           36dB (0x48 0xd2)
       SNR (SQI):           36dB (0x49 0x6f)
       SNR (SQI):           36dB (0x49 0x13)
       SNR (SQI):           36dB (0x49 0x27)
       SNR (SQI):           36dB (0x49 0x2f)
       SNR (SQI):           36dB (0x49 0x4a)
       SNR (SQI):           36dB (0x49 0x96)
       SNR (SQI):           36dB (0x49 0x80)
       SNR (SQI):           36dB (0x49 0x94)
       SNR (SQI):           36dB (0x49 0x4d)
       SNR (SQI):           36dB (0x48 0xf1)
       SNR (SQI):           36dB (0x49 0x4e)
       SNR (SQI):           36dB (0x49 0x84)
       SNR (SQI):           36dB (0x48 0x9a)
       SNR (SQI):           36dB (0x49 0xf)
       SNR (SQI):           36dB (0x49 0x78)
       SNR (SQI):           36dB (0x48 0x9a)
       SNR (SQI):           36dB (0x48 0xdc)
       SNR (SQI):           36dB (0x48 0xef)
       SNR (SQI):           36dB (0x49 0x4d)
       SNR (SQI):           36dB (0x48 0xe4)
       SNR (SQI):           36dB (0x48 0xe8)
       SNR (SQI):           36dB (0x48 0x6a)
       SNR (SQI):           36dB (0x48 0x4c)
       SNR (SQI):           36dB (0x48 0xf4)
       SNR (SQI):           36dB (0x49 0x12)
       SNR (SQI):           36dB (0x48 0xd1)
       SNR (SQI):           36dB (0x48 0xae)
       SNR (SQI):           36dB (0x48 0xda)
       SNR (SQI):           36dB (0x48 0x6c)
       SNR (SQI):           36dB (0x48 0x2a)
       SNR (SQI):           36dB (0x48 0x8a)
       SNR (SQI):           36dB (0x48 0xca)
       SNR (SQI):           35dB (0x48 0x6a)
       SNR (SQI):           36dB (0x47 0xe7)
       SNR (SQI):           36dB (0x48 0x54)
       SNR (SQI):           36dB (0x48 0xc7)
       SNR (SQI):           36dB (0x48 0x78)
       SNR (SQI):           36dB (0x48 0x3a)
       SNR (SQI):           36dB (0x48 0x42)
       SNR (SQI):           35dB (0x47 0xf3)
       SNR (SQI):           36dB (0x47 0xee)
       SNR (SQI):           36dB (0x48 0x26)
       SNR (SQI):           36dB (0x48 0x7c)
       SNR (SQI):           36dB (0x48 0x30)
       SNR (SQI):           35dB (0x48 0x19)
       SNR (SQI):           36dB (0x47 0xdf)
       SNR (SQI):           36dB (0x47 0xc8)
       SNR (SQI):           36dB (0x48 0x18)
       SNR (SQI):           36dB (0x48 0x1f)
       SNR (SQI):           36dB (0x47 0xee)
       SNR (SQI):           36dB (0x48 0x96)
       SNR (SQI):           36dB (0x48 0x63)
       SNR (SQI):           36dB (0x48 0xb8)
       SNR (SQI):           35dB (0x47 0xf8)
       SNR (SQI):           35dB (0x47 0xbb)
       SNR (SQI):           36dB (0x48 0x31)
       SNR (SQI):           36dB (0x47 0xf7)
       SNR (SQI):           36dB (0x48 0xb6)
       SNR (SQI):           36dB (0x48 0x54)
       SNR (SQI):           36dB (0x48 0x88)
       SNR (SQI):           36dB (0x48 0x7)
       SNR (SQI):           36dB (0x48 0x7e)
       SNR (SQI):           36dB (0x49 0x11)
       SNR (SQI):           36dB (0x48 0x7b)
       SNR (SQI):           36dB (0x48 0xd3)
       SNR (SQI):           36dB (0x48 0xec)
       SNR (SQI):           36dB (0x48 0xdd)
       SNR (SQI):           36dB (0x48 0xa7)
       SNR (SQI):           36dB (0x49 0x20)
       SNR (SQI):           36dB (0x48 0xbb)
       SNR (SQI):           36dB (0x49 0x5d)
       SNR (SQI):           36dB (0x48 0xf0)
       SNR (SQI):           36dB (0x49 0x15)
       SNR (SQI):           36dB (0x49 0x2a)
       SNR (SQI):           36dB (0x49 0x15)
       SNR (SQI):           36dB (0x49 0x9b)
       SNR (SQI):           36dB (0x48 0xa8)
       SNR (SQI):           36dB (0x49 0xf)
       SNR (SQI):           36dB (0x49 0x69)
       SNR (SQI):           36dB (0x49 0x8d)
       SNR (SQI):           36dB (0x48 0xe2)
    Does anyone have any ideas what the hex digits refer to? I'm curious as to why that 2nd byte is changing so much.

  2. #2
    Join Date
    Dec 2004
    Posts
    831
    My guess would be the value in parenthesis is a linear measurement of the noise value. By definition noise has a random amplitude, while a modulated carrier (unless it si a sideband transmission, which this is not) is ordinarily quite steady in terms of amplitude. The difference between the lowest and highest values you show is less than .04dB if the measurement is in power and .08dB if the measurement is in voltage. Either way, it's not a significant variation. Of course, I could be wrong and the number could mean something else entirely, but I would think it's just the least significant byte of the linear measurement of the noise.
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