7.21. The SI476x Driver

Copyright © 2013 Andrey Smirnov <andrew.smirnov@gmail.com>

7.21.1. TODO for the driver

  • According to the SiLabs’ datasheet it is possible to update the firmware of the radio chip in the run-time, thus bringing it to the most recent version. Unfortunately I couldn’t find any mentioning of the said firmware update for the old chips that I tested the driver against, so for chips like that the driver only exposes the old functionality.

7.21.2. Parameters exposed over debugfs

SI476x allow user to get multiple characteristics that can be very useful for EoL testing/RF performance estimation, parameters that have very little to do with V4L2 subsystem. Such parameters are exposed via debugfs and can be accessed via regular file I/O operations.

The drivers exposes following files:

  • /sys/kernel/debug/<device-name>/acf This file contains ACF(Automatically Controlled Features) status information. The contents of the file is binary data of the following layout:

    Offset

    Name

    Description

    0x00

    blend_int

    Flag, set when stereo separation has crossed below the blend threshold

    0x01

    hblend_int

    Flag, set when HiBlend cutoff frequency is lower than threshold

    0x02

    hicut_int

    Flag, set when HiCut cutoff frequency is lower than threshold

    0x03

    chbw_int

    Flag, set when channel filter bandwidth is less than threshold

    0x04

    softmute_int

    Flag indicating that softmute attenuation has increased above softmute threshold

    0x05

    smute

    0 - Audio is not soft muted 1 - Audio is soft muted

    0x06

    smattn

    Soft mute attenuation level in dB

    0x07

    chbw

    Channel filter bandwidth in kHz

    0x08

    hicut

    HiCut cutoff frequency in units of 100Hz

    0x09

    hiblend

    HiBlend cutoff frequency in units of 100 Hz

    0x10

    pilot

    0 - Stereo pilot is not present 1 - Stereo pilot is present

    0x11

    stblend

    Stereo blend in %

  • /sys/kernel/debug/<device-name>/rds_blckcnt This file contains statistics about RDS receptions. It’s binary data has the following layout:

    Offset

    Name

    Description

    0x00

    expected

    Number of expected RDS blocks

    0x02

    received

    Number of received RDS blocks

    0x04

    uncorrectable

    Number of uncorrectable RDS blocks

  • /sys/kernel/debug/<device-name>/agc This file contains information about parameters pertaining to AGC(Automatic Gain Control)

    The layout is:

    Offset

    Name

    Description

    0x00

    mxhi

    0 - FM Mixer PD high threshold is not tripped 1 - FM Mixer PD high threshold is tripped

    0x01

    mxlo

    ditto for FM Mixer PD low

    0x02

    lnahi

    ditto for FM LNA PD high

    0x03

    lnalo

    ditto for FM LNA PD low

    0x04

    fmagc1

    FMAGC1 attenuator resistance (see datasheet for more detail)

    0x05

    fmagc2

    ditto for FMAGC2

    0x06

    pgagain

    PGA gain in dB

    0x07

    fmwblang

    FM/WB LNA Gain in dB

  • /sys/kernel/debug/<device-name>/rsq This file contains information about parameters pertaining to RSQ(Received Signal Quality)

    The layout is:

    Offset

    Name

    Description

    0x00

    multhint

    0 - multipath value has not crossed the Multipath high threshold 1 - multipath value has crossed the Multipath high threshold

    0x01

    multlint

    ditto for Multipath low threshold

    0x02

    snrhint

    0 - received signal’s SNR has not crossed high threshold 1 - received signal’s SNR has crossed high threshold

    0x03

    snrlint

    ditto for low threshold

    0x04

    rssihint

    ditto for RSSI high threshold

    0x05

    rssilint

    ditto for RSSI low threshold

    0x06

    bltf

    Flag indicating if seek command reached/wrapped seek band limit

    0x07

    snr_ready

    Indicates that SNR metrics is ready

    0x08

    rssiready

    ditto for RSSI metrics

    0x09

    injside

    0 - Low-side injection is being used 1 - High-side injection is used

    0x10

    afcrl

    Flag indicating if AFC rails

    0x11

    valid

    Flag indicating if channel is valid

    0x12

    readfreq

    Current tuned frequency

    0x14

    freqoff

    Signed frequency offset in units of 2ppm

    0x15

    rssi

    Signed value of RSSI in dBuV

    0x16

    snr

    Signed RF SNR in dB

    0x17

    issi

    Signed Image Strength Signal indicator

    0x18

    lassi

    Signed Low side adjacent Channel Strength indicator

    0x19

    hassi

    ditto for High side

    0x20

    mult

    Multipath indicator

    0x21

    dev

    Frequency deviation

    0x24

    assi

    Adjacent channel SSI

    0x25

    usn

    Ultrasonic noise indicator

    0x26

    pilotdev

    Pilot deviation in units of 100 Hz

    0x27

    rdsdev

    ditto for RDS

    0x28

    assidev

    ditto for ASSI

    0x29

    strongdev

    Frequency deviation

    0x30

    rdspi

    RDS PI code

  • /sys/kernel/debug/<device-name>/rsq_primary This file contains information about parameters pertaining to RSQ(Received Signal Quality) for primary tuner only. Layout is as the one above.