Using a DVBSky T982 PCIe card under Linux

Using a DVBSky T982 PCIe card under Linux

I recently acquired a DVBSky T982 DVB-T / DVB-C decoder card (it was already fitted in a machine I bought second-hard for other reasons). It's based on a Conexant CX23885 decoder and a Silicon Labs Si2168 demodulator.

I'm trying to get it working under Linux (Debian 10 Buster / Devuan 3 Beowulf kernel 4.19.0-10) and this is a bit of a story about how it's not obvious (even though it's actually easy) to do this.

I've used scan, dvbscan and w_scan, and none of them find any channels. I have a DVB-T antenna plugged into one input socket on the card, and a DVB-C feed from my local provider NetCologne plugged into the other. I know that the NetCologne feed provides multiple digital TV channels because it works nicely on my LG 42LH4000 television.

Firmware

I've installed the firmware package firmware-misc-nonfree and I can see the card being detected and set up in dmesg:

[    7.571465] cx23885: cx23885 driver version 0.0.4 loaded
[    7.571708] cx23885: CORE cx23885[0]: subsystem: 4254:0982, board: DVBSky T982 [card=51,autodetected]
[    7.812110] IPv6: ADDRCONF(NETDEV_UP): eth0: link is not ready
[    7.854515] cx25840 12-0044: cx23885 A/V decoder found @ 0x88 (cx23885[0])
[    7.876695] cx25840 12-0044: firmware: direct-loading firmware v4l-cx23885-avcore-01.fw
[    8.494100] cx25840 12-0044: loaded v4l-cx23885-avcore-01.fw firmware (16382 bytes)
[    8.509383] cx23885: cx23885_dvb_register() allocating 1 frontend(s)
[    8.509392] cx23885: cx23885[0]: cx23885 based dvb card
[    8.534800] i2c i2c-11: Added multiplexed i2c bus 13
[    8.534806] si2168 11-0064: Silicon Labs Si2168-A30 successfully identified
[    8.534810] si2168 11-0064: firmware version: A 3.0.2
[    8.545398] si2157 13-0060: Silicon Labs Si2147/2148/2157/2158 successfully attached
[    8.545426] dvbdev: DVB: registering new adapter (cx23885[0])
[    8.545432] cx23885 0000:03:00.0: DVB: registering adapter 0 frontend 0 (Silicon Labs Si2168)...
[    8.573687] cx23885: DVBSky T982 port 1 MAC address: 00:17:42:54:09:87
[    8.573691] cx23885: cx23885_dvb_register() allocating 1 frontend(s)
[    8.573693] cx23885: cx23885[0]: cx23885 based dvb card
[    8.584315] i2c i2c-10: Added multiplexed i2c bus 14
[    8.584321] si2168 10-0064: Silicon Labs Si2168-A30 successfully identified
[    8.584324] si2168 10-0064: firmware version: A 3.0.2
[    8.589796] si2157 14-0060: Silicon Labs Si2147/2148/2157/2158 successfully attached
[    8.589825] dvbdev: DVB: registering new adapter (cx23885[0])
[    8.589832] cx23885 0000:03:00.0: DVB: registering adapter 1 frontend 0 (Silicon Labs Si2168)...
[    8.618175] cx23885: DVBSky T982 port 2 MAC address: 00:17:42:54:09:88
[    8.618181] cx23885: cx23885_dev_checkrevision() Hardware revision = 0xa5
[    8.618188] cx23885: cx23885[0]/0: found at 0000:03:00.0, rev: 4, irq: 16, latency: 0, mmio: 0xfe600000

Devices

This gives me two adapters under /dev/dvb:

# ls -alR /dev/dvb
/dev/dvb:
total 0
drwxr-xr-x  4 root root   80 Apr  2 17:59 .
drwxr-xr-x 18 root root 3600 Apr  2 17:59 ..
drwxr-xr-x  2 root root  120 Apr  2 17:59 adapter0
drwxr-xr-x  2 root root  120 Apr  2 17:59 adapter1

/dev/dvb/adapter0:
total 0
drwxr-xr-x 2 root root     120 Apr  2 17:59 .
drwxr-xr-x 4 root root      80 Apr  2 17:59 ..
crw-rw---- 1 root video 212, 1 Apr  2 17:59 demux0
crw-rw---- 1 root video 212, 2 Apr  2 17:59 dvr0
crw-rw---- 1 root video 212, 0 Apr  2 17:59 frontend0
crw-rw---- 1 root video 212, 3 Apr  2 17:59 net0

/dev/dvb/adapter1:
total 0
drwxr-xr-x 2 root root     120 Apr  2 17:59 .
drwxr-xr-x 4 root root      80 Apr  2 17:59 ..
crw-rw---- 1 root video 212, 5 Apr  2 17:59 demux0
crw-rw---- 1 root video 212, 6 Apr  2 17:59 dvr0
crw-rw---- 1 root video 212, 4 Apr  2 17:59 frontend0
crw-rw---- 1 root video 212, 7 Apr  2 17:59 net0

I have no idea whether the top connector on the card corresponds to adapter0 or adapter1, but I have no reason to believe that one of them is for DVB-T and the other for DVB-C, so I've just plugged in the antenna and the cable feed and tried to scan for channels.

Edit: it turns out that adapter0 is the top connector, and adapter1 is the bottom connector. It also turns out that no, they're not specific to DVB-T or -C: both connectors can do both types of signal.

More firmware

I just spotted that firmware-misc-nonfree clearly isn't sufficient. Whilst I'm doing a scan, the following turns up in dmesg / syslog:

[76759.199059] si2168 10-0064: firmware: failed to load dvb-demod-si2168-a30-01.fw (-2)
[76759.199164] si2168 10-0064: Direct firmware load for dvb-demod-si2168-a30-01.fw failed with error -2
[76759.199171] si2168 10-0064: firmware file 'dvb-demod-si2168-a30-01.fw' not found

A bit of a Google search turns up a forum page telling me where I can download this firmware file, and also another one which seems to be related. So, I've downloaded those, put them into /lib/firmware and tried again (initially without a reboot), and this time a scan puts into syslog:

[77900.749275] si2168 11-0064: firmware: direct-loading firmware dvb-demod-si2168-a30-01.fw
[77900.749287] si2168 11-0064: downloading firmware from file 'dvb-demod-si2168-a30-01.fw'
[77903.797846] si2168 11-0064: firmware version: � 3.0.16

This looks more promising, however so far it still hasn't encouraged anything to work.

Progress!

# rmmod cx23885
# modprobe cx23885

This now causes a scan process to load not only the 'demod' firmware but also the 'tuner' firmware, and this does help.

[80185.675356] si2168 11-0064: firmware: direct-loading firmware dvb-demod-si2168-a30-01.fw
[80185.675367] si2168 11-0064: downloading firmware from file 'dvb-demod-si2168-a30-01.fw'
[80188.719879] si2168 11-0064: firmware version: � 3.0.16
[80188.731366] si2157 13-0060: found a 'Silicon Labs Si2158-A20'
[80188.731440] si2157 13-0060: firmware: direct-loading firmware dvb-tuner-si2158-a20-01.fw
[80188.731445] si2157 13-0060: downloading firmware from file 'dvb-tuner-si2158-a20-01.fw'
[80189.731408] si2157 13-0060: firmware version: 2.1.9

scan now gives me a considerable quantity of output for DVB-C, as expected from the number of channels NetCologne provides, but nothing for DVB-T…

dvbscan still produces nothing, but then most of the documentation says that one of the tools scan and dvbscan will work, and the other one won't, with any given adapter, so I'm not too surprised.

w_scan gives plenty of output, for both DVB-T and DVB-C.

This is what I get in Cologne, Germany at Easter 2021:

DVB-T full output from command, channel list in mplayer format
DVB-C full output from command, channel list in mplayer format

You might then want to use a recording script which can record now, or later, for a specified duration, on a specified channel.

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