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by jdb
Mon Oct 16, 2017 8:57 pm
Forum: Advanced users
Topic: Analogue audio redux
Replies: 11
Views: 477

Re: Analogue audio redux

By default, omxplayer has 0dB gain. The default setting for ALSA is -20dB and can be adjusted through alsamixer - the setting will persist across a reboot. Even at "0dB" line level, the Pi 3.5mm jack typically outputs voltage levels lower than the equivalent line level as the source impedance is not...
by jdb
Mon Oct 16, 2017 1:24 pm
Forum: Advanced users
Topic: What is "the software i2c controller"
Replies: 1
Views: 83

Re: What is "the software i2c controller"

The i2c-gpio overlays bind a bitbashing I2C driver to the respective GPIO pins. The "software" element is provided by the Linux kernel and it emulates the I2C protocol by reading pin state and driving the output "low" when necessary. It's considerably slower than the I2C hardware peripheral but is g...
by jdb
Sat Oct 14, 2017 2:58 pm
Forum: Advanced users
Topic: Analogue audio redux
Replies: 11
Views: 477

Re: Analogue audio redux

Ah, cclive downloads a VP8/vorbis encoded video whereas youtube-dl retrieves h264/aac encoded. With start_x=1 omxplayer plays it. It still doesn't break for me, though. I'm using the latest omxplayer from Raspbian Stretch. omxplayer - Commandline multimedia player for the Raspberry Pi Build date: We...
by jdb
Sat Oct 14, 2017 1:47 pm
Forum: Advanced users
Topic: Analogue audio redux
Replies: 11
Views: 477

Re: Analogue audio redux

Following that link, I get a blank webpage?

If I run youtube-dl on just the root URL, it downloads a 360p video that appears to play OK.
Can you upload your copy to e.g. dropbox? There's no guarantee Youtube will serve me the same file as you got.
by jdb
Wed Oct 11, 2017 11:08 pm
Forum: Advanced users
Topic: Analogue audio testing
Replies: 265
Views: 83665

Re: Analogue audio testing

Please continue discussion/testing in the new thread -> viewtopic.php?f=29&t=195178
by jdb
Wed Oct 11, 2017 11:07 pm
Forum: Advanced users
Topic: Analogue audio redux
Replies: 11
Views: 477

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. The analogue signal-to-noise ratio now approaches CD quality with...
by jdb
Sun Oct 08, 2017 2:57 pm
Forum: General discussion
Topic: RPi3B FishEye Pink Noise
Replies: 1
Views: 112

Re: RPi3B FishEye Pink Noise

That is not a Raspberry Pi camera product. As such there's no guarantee it will work at all with the Pi.

That said, how long is the connecting ribbon cable between the Pi and the camera? A shorter cable may yield better results.
by jdb
Sat Sep 16, 2017 11:27 pm
Forum: General discussion
Topic: The one and only change I would make to the Raspberry Pi
Replies: 38
Views: 1557

Re: The one and only change I would make to the Raspberry Pi

Wait what, are we arguing about the GPIO connector on the Pi now?
Locked. Obviously.
by jdb
Wed Sep 13, 2017 4:28 pm
Forum: Advanced users
Topic: Analogue audio testing
Replies: 265
Views: 83665

Re: Analogue audio testing

I'm currently in the middle of rewriting the buffer handling code to allow for firmware-side mixing, so it's possible that the next release will incidentally fix the issue. Can you attempt capture of a glitch? If you have a USB sound card (or pc) with line-in port, can you connect the Pi audio outpu...
by jdb
Tue Sep 12, 2017 11:35 am
Forum: General discussion
Topic: What you ABSOLUTELY DONT WANT to see in Raspberry Pi 4?
Replies: 1
Views: 410

Re: What you ABSOLUTELY DONT WANT to see in Raspberry Pi 4?

Cute variation on a theme here...

But this thread is just asking for trouble. As such, locked.
by jdb
Tue Sep 12, 2017 10:14 am
Forum: Troubleshooting
Topic: USB-to-UART converter dropping data
Replies: 8
Views: 281

Re: USB-to-UART converter dropping data

It may be worth jumping forwards rather than backwards as there have been several releases since 4.9. Can you build a 4.12 kernel from https://github.com/raspberrypi/linux (it's had more testing than 4.13) and see if the regression is still present? https://www.raspberrypi.org/documentation/linux/ke...
by jdb
Mon Sep 11, 2017 3:39 pm
Forum: Troubleshooting
Topic: USB-to-UART converter dropping data
Replies: 8
Views: 281

Re: USB-to-UART converter dropping data

Milliseconds of latency doesn't sound like hardIRQ contention (which would be a lot more obvious in other ways). This may actually be related to a bug (from upstream, recently fixed in 4.9) that was affecting DVB-T and SDR dongles. A dodgy timer interrupt calculation would produce wrong values for s...
by jdb
Mon Sep 11, 2017 2:49 pm
Forum: Troubleshooting
Topic: USB-to-UART converter dropping data
Replies: 8
Views: 281

Re: USB-to-UART converter dropping data

From the USB driver rewrite thread (which should probably be transposed to the site docs at some point): https://www.raspberrypi.org/forums/viewtopic.php?t=70437 See point 4. and 5. about USB-serial performance. Edit: hm, seems like you're still seeing issues. If you're getting sporadic data loss, t...
by jdb
Mon Sep 11, 2017 2:44 pm
Forum: Troubleshooting
Topic: Async Rising/Falling Edge hanging on 1mhz signal
Replies: 6
Views: 276

Re: Async Rising/Falling Edge hanging on 1mhz signal

Hm. Does the async edge interrupt freeze at ANY frequency or is it just high frequency that is needed to lock up the system? If you give the ARM 1 million interrupts per second, it's not going to be able to do anything that isn't interrupt handling. Note that a single core handles all interrupts (wi...
by jdb
Mon Sep 11, 2017 2:38 pm
Forum: General discussion
Topic: Voltage port usb raspberry pi 3 model b
Replies: 1
Views: 112

Re: Voltage port usb raspberry pi 3 model b

Yes. By default (i.e. at power-on), the LAN9514 hub chip is held in the reset state which powers off the USB ports. If you haven't enabled USB mass-storage /Ethernet booting via the OTP setting, the reset will only be released after the SDcard bootcode has been loaded.
by jdb
Mon Sep 11, 2017 2:31 pm
Forum: General discussion
Topic: Recent forum moderation not in line with Foundation's constitution?
Replies: 5
Views: 360

Re: Recent forum moderation not in line with Foundation's constitution?

Totally agreed. I know how difficult it is. I have moderated on other technical forums for many years. Learning how to use computers and trouble-shooting problems on them is learning - even when not on pi computers. Shutting down people looking for help just feels wrong. So we should open the off-t...
by jdb
Mon Sep 11, 2017 12:53 pm
Forum: Advanced users
Topic: Analogue audio testing
Replies: 265
Views: 83665

Re: Analogue audio testing

The SDRAM recalibration was on a 500ms interval, so that isn't causing your problem. What other things are running on the Pi? Typically you may run into FIFO underflow (that causes the ticks) if you are running GPU-intensive applications or are using high-quality HD deinterlace. Both of these put lo...
by jdb
Thu Aug 31, 2017 5:06 pm
Forum: Troubleshooting
Topic: USB to Serial connection loosing chars on Pi but not windows
Replies: 9
Views: 366

Re: USB to Serial connection loosing chars on Pi but not windows

dwc_otg.nak_holdoff=0 is not a recommended setting. It will cause an excess of interrupts which will negatively impact performance. It also implicitly disables certain code paths in the driver; if there is a bug in the default setting then I want to know. Can you please re-test with dwc_otg.nak_hold...
by jdb
Thu Aug 31, 2017 12:18 pm
Forum: Troubleshooting
Topic: USB to Serial connection loosing chars on Pi but not windows
Replies: 9
Views: 366

Re: USB to Serial connection loosing chars on Pi but not windows

Don't set dwc_otg.speed=1, this will clobber all throughput to 12mbit/s or less.

What happens if you set dwc_otg.nak_holdoff=2 in /boot/cmdline.txt?
by jdb
Wed Aug 30, 2017 3:20 pm
Forum: General discussion
Topic: EMC emission at 200mhz
Replies: 31
Views: 4428

Re: EMC emission at 200mhz

If you have wires (actual flying leads?) plugged into the GPIO then yes, they will act as quite good antennae for any RF frequencies otherwise contained within the Pi. Note that there is *no* RF filtering on any of the GPIO pins on the connector as they run straight to the SoC. The general design ch...
by jdb
Sat Aug 26, 2017 11:15 am
Forum: General discussion
Topic: Interesting to see what RPF has been up against
Replies: 14
Views: 964

Re: Interesting to see what RPF has been up against

It's a pretty open "secret" that China's government heavily subsidises export-based industries to prop up their (huge) manufacturing base. It's slowly going increasingly against the grain though, as despite the Yuan being fixed to other currencies by the central bank[1] the current account balance t...
by jdb
Thu Aug 24, 2017 3:54 pm
Forum: Advanced users
Topic: Analogue audio testing
Replies: 265
Views: 83665

Re: Analogue audio testing

I'm now in a position where I have some time available to look at this, so I can start fixing bugs Soon(tm) with a view to enabling this by default. I've spotted one potential reason why Chromium/multiple writers aren't working - assuming my hunch is correct about how the firmware is handling separa...
by jdb
Tue Aug 08, 2017 7:50 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: ADC Sampling 4 channels @ 100kHz
Replies: 6
Views: 533

Re: ADC Sampling 4 channels @ 100kHz

I'm assuming you're starting a conversion and then reading the result, i.e. you need 10uS-precise access to the SPI peripheral. Isolcpus is an imperfect solution to the problem. Isolcpus will prevent the kernel userspace scheduler from running userspace processes on a specific core, but kernel threa...
by jdb
Tue Jul 25, 2017 8:48 pm
Forum: General discussion
Topic: STICKY: NEW FORUM SKIN - Comments here please.
Replies: 281
Views: 17580

Re: STICKY: NEW FORUM SKIN - Comments here please.

These comments refer to the UI elements of the theme that was presented to me by default on login. For reference I am using Firefox 54.0.1. There is no indication that drop-down lists are drop-down lists (e.g. UCP / board preferences / my board style). They are rendered the same as context tabs and ...
by jdb
Wed Jul 12, 2017 3:22 pm
Forum: General discussion
Topic: harvard architecture or von neumann architecture?
Replies: 4
Views: 563

Re: harvard architecture or von neumann architecture?

Architecturally, the Pi's ARM is a Von Neumann design (i.e. there is nothing preventing you from using the processor to write data to the addresses that contain other instructions) but there are certain Harvard-like elements in implementation. In the ARM1176, A7, and A53 cores there are two data por...

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