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by jdb
Wed Feb 14, 2018 12:37 pm
Forum: Advanced users
Topic: Moving Linux kernel to 4.14
Replies: 55
Views: 10648

Re: Moving Linux kernel to 4.14

Regarding the crash on boot with USB, there's a clue in what each CPU is doing. CPU1 just entered the FIQ handler, and CPU2 is in dwc_otg_driver_init(). I think there may be some racy behaviour between taking an interrupt too early and the coherence of the driver state. I note that the USB register ...
by jdb
Mon Feb 12, 2018 10:23 am
Forum: General discussion
Topic: Secure online banking
Replies: 14
Views: 3321

Re: Secure online banking

You need to be careful or your little hobby project might result in a security risk that acts as an entry point into your network. They can’t perform secure booting such as ARM Trustzone, and the SD card and operating system are not easily encrypted. What benefit would having an encrypted operating...
by jdb
Wed Feb 07, 2018 4:52 pm
Forum: Advanced users
Topic: Analogue audio redux
Replies: 39
Views: 5226

Re: Analogue audio redux

We are planning to move to 4.14 in Raspbian in the next few days, which will include this driver (enabled by default) -> viewtopic.php?f=29&t=197689&start=25#p1269469
by jdb
Mon Jan 29, 2018 10:11 am
Forum: Advanced users
Topic: Ok to have a 3m shielded serial cable?
Replies: 7
Views: 444

Re: Ok to have a 3m shielded serial cable?

If you're transmitting serially over a potentially noisy environment, use an RS-422 transceiver at each end. Not only will it work properly with the twisted pair cable, it will be hardened against cable faults and "wandering ground" effects. The GPIOs are not suitable for transmitting signals over a...
by jdb
Tue Jan 23, 2018 6:44 pm
Forum: General discussion
Topic: Next Gen Raspberry: Joint venture?
Replies: 17
Views: 795

Re: Next Gen Raspberry: Joint venture?

Not interesting at all. Just random specultion without any information content. As pops up here every week. Yep. I especially like the part about Broadcom (subsidiary of Avago) - a $107billion market cap company with thousands of employees - colluding with a company FOUR ORDERS OF MAGNITUDE SMALLER...
by jdb
Fri Jan 19, 2018 5:41 pm
Forum: Advanced users
Topic: Analogue audio redux
Replies: 39
Views: 5226

Re: Analogue audio redux

Not officially, no. It's normally the case that an updated apt-get firmware is made available at the same time as a Raspbian distribution release.
by jdb
Fri Jan 19, 2018 2:42 pm
Forum: Advanced users
Topic: Analogue audio redux
Replies: 39
Views: 5226

Re: Analogue audio redux

Available in latest rpi-update firmware is a PWM audio driver that significantly increases the audio quality available from the 3.5mm TRRS jack. To enable the advanced audio driver, add audio_pwm_mode=2 to /boot/config.txt and reboot. Hi all, many thanks to jdb for this driver. Is there a way to us...
by jdb
Fri Jan 19, 2018 1:00 pm
Forum: Advanced users
Topic: Analogue audio redux
Replies: 39
Views: 5226

Re: Analogue audio redux

Odd. The ALSA driver should happily accept mono streams. pi@raspberrypi:~$ speaker-test -c 1 -t sine speaker-test 1.1.3 Playback device is default Stream parameters are 48000Hz, S16_LE, 1 channels Sine wave rate is 440.0000Hz Does the behaviour definitely change from working -> not working on the sa...
by jdb
Thu Jan 04, 2018 12:19 pm
Forum: General discussion
Topic: Chip architecture - is the Pi vulnerable?
Replies: 46
Views: 3535

Re: Chip architecture - is the Pi vulnerable?

Interestingly, this exploit chain works solely because of the unintended side effects of having a processor that's "clever". For example, one step of the exploit chain that allows for reading of arbitrary process memory requires that you corrupt the branch prediction state by deliberately causing co...
by jdb
Mon Dec 11, 2017 12:09 pm
Forum: General discussion
Topic: USB 3.0 support
Replies: 36
Views: 110557

Re: USB 3.0 support

Don't necro old threads.

Especially with inane one-line responses.
by jdb
Thu Dec 07, 2017 11:49 am
Forum: Troubleshooting
Topic: Official Raspberry Pi power supply unusable for acquiring audio
Replies: 14
Views: 839

Re: Official Raspberry Pi power supply unusable for acquiring audio

Is the source of your audio also mains-powered?
by jdb
Wed Dec 06, 2017 10:53 am
Forum: Advanced users
Topic: Analogue audio redux
Replies: 39
Views: 5226

Re: Analogue audio redux

I would guess that the wire going to the GPIO is coupling noise into somewhere on the amp PCB.

You can buy in-line isolation transformers (ground loop isolators) that block differring ground potentials but pass audio frequencies.
by jdb
Fri Dec 01, 2017 9:59 pm
Forum: Advanced users
Topic: Raspberry Pi Zero W: Interference on 3.3V line when transmitting data over Wifi
Replies: 5
Views: 621

Re: Raspberry Pi Zero W: Interference on 3.3V line when transmitting data over Wifi

You will see the same behaviour on all models of Pi that use switching regulators for 3v3 (i.e. everything from B+ onwards), even if they don't have wifi chipsets. In the case of the Pi Zero W there are two principal consumers of power on the 3v3 line that produce quite prominent load steps - the SD...
by jdb
Wed Nov 22, 2017 5:49 pm
Forum: Off topic discussion
Topic: [SOLVED] Question about some VERY old LED displays
Replies: 11
Views: 1260

Re: Question about some VERY old LED displays

Do you have a multimeter with diode tester functionality? Testing N pins to every other pin in turn (for NxN tests, both polarity - or fewer once you find the common anode or cathode) would tell you the connection and orientation of each diode. The LED will also glow faintly in the forward-biased di...
by jdb
Wed Nov 22, 2017 2:56 pm
Forum: Advanced users
Topic: Analogue audio redux
Replies: 39
Views: 5226

Re: Analogue audio redux

You can replace the firmware without changing the kernel. If there's a big version jump, certain devicetree changes may break certain things in Linux. Good to know you got it working.
by jdb
Tue Nov 14, 2017 2:08 pm
Forum: General discussion
Topic: RPi B+
Replies: 4
Views: 210

Re: RPi B+

RS and Premier Farnell independently manufacture Pi models B+/2/3 via contract electronics manufacturers (mainly at Sony's manufacturing plant in south Wales). There is no forward authorisation or compulsion on the part of Raspberry Pi for manufacture, only a licensing agreement that requires a fee ...
by jdb
Tue Nov 14, 2017 1:57 pm
Forum: General discussion
Topic: RPi B+
Replies: 4
Views: 210

Re: RPi B+

http://uk.farnell.com/raspberry-pi/raspberry-modb-512m/raspberry-pi-model-b-board/dp/2456986 "601 in stock." "More stock available week commencing 06/04/2018" So, I'd say yes? As is typical with lower-volume mass-produced parts, lead times increase as demand drops. If you're looking for extended ava...
by jdb
Mon Nov 13, 2017 10:57 am
Forum: Beginners
Topic: Noise isolation via Ferrite Beads
Replies: 6
Views: 516

Re: Noise isolation via Ferrite Beads

by jdb
Sat Nov 04, 2017 11:37 am
Forum: Advanced users
Topic: Strange sound in audio output
Replies: 9
Views: 737

Re: Hardware PWM issues

Topic split from the audio driver thread. The issues listed are not related to the new VPU-side PWM audio driver.
by jdb
Fri Nov 03, 2017 10:35 pm
Forum: General discussion
Topic: Moving to another plataform to have 10-bit content support
Replies: 5
Views: 738

Re: Moving to another plataform to have 10-bit content support

Since you are awash with cash, and have no qualms about paying over the odds for esoteric features - best of luck to you.

Thread locked.
by jdb
Thu Nov 02, 2017 9:17 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: GPIO max current
Replies: 34
Views: 67191

Re: GPIO max current

One thing I have always wondered: if some of the GPIOs are sourcing current and others are sinking, then does the 50mA limit apply to the sum of the absolute currents, or to the maximum of source and sink? It's a function of both. If your GPIO pad is sourcing current, then it's effectively connecti...
by jdb
Wed Oct 25, 2017 3:17 pm
Forum: Troubleshooting
Topic: Rpi3 audio - Low buzz
Replies: 4
Views: 291

Re: Rpi3 audio - Low buzz

If you need to use HDMI at the same time as the DAC, you can buy ground loop "isolators" for in-line suppression, e.g. https://www.amazon.co.uk/AV-Link-Ground ... B000NVWB9O

They're basically 1:1 transformers that break the ground return between input-output.
by jdb
Wed Oct 25, 2017 2:38 pm
Forum: Troubleshooting
Topic: Rpi3 audio - Low buzz
Replies: 4
Views: 291

Re: Rpi3 audio - Low buzz

If you have both the HDMI and DAC connected, you may be hearing the effects of a ground loop. Plugtop PSUs are usually double insulated (so no connection to earth return) but it's likely your amp and TV both have earth return connections. What happens to the noise level if you unplug HDMI with DAC p...
by jdb
Tue Oct 24, 2017 10:56 am
Forum: Troubleshooting
Topic: bcm2835-aux-uart 20215040.serial: could not get clk: -517
Replies: 13
Views: 2920

Re: bcm2835-aux-uart 20215040.serial: could not get clk: -517

The warning is harmless. Linux will load drivers in a non-deterministic order as we're booting on multiple CPUs. The -517 error is defined as "-EPROBE_DEFER" which means "try again later, the requested resource isn't set up yet". Your UART not working is likely to be a different issue. Are you sure ...
by jdb
Wed Oct 18, 2017 1:55 pm
Forum: Advanced users
Topic: Analogue audio redux
Replies: 39
Views: 5226

Re: Analogue audio redux

The HDMI monitor will still work as the framebuffer is just a memory-mapped location that's scanned out by HVS. The ARM can freely write to the memory without GPU interaction. If the GPU has crashed then vcgencmd won't return anything useful. Is the ACT LED flashing in a regular pattern? If you're s...

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