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by jdb
Sat Aug 11, 2018 8:58 pm
Forum: Advanced users
Topic: dtoverlay=dht11?
Replies: 4
Views: 127

Re: dtoverlay=dht11?

The "protocol" used by the DHT sensors is a bit tedious. They respond with a variable-length pulse-position modulated signal that has quite a small timebase - 20uS - and the Pi sometimes misses these pulses resulting in a failed decode. A while ago I did try submitting an upstream patch that increas...
by jdb
Thu Aug 09, 2018 3:48 pm
Forum: Off topic discussion
Topic: Any NAS chassis reccomendations ?
Replies: 6
Views: 240

Re: Any NAS chassis reccomendations ?

Older HP MIcroserver running Nas4Free (hmm, looks like it has been renamed to XigmaNas ). I've got an N36L and an N40 that have been chuntering away in corners for about 6 years. Ebuyer were selling them at around £120 with HP then offering cashback! +1 for HP microserver. I got a Gen 8 when they w...
by jdb
Wed Aug 08, 2018 10:13 am
Forum: Advanced users
Topic: What value are those parts?
Replies: 36
Views: 922

Re: What value are those parts?

hippy wrote:
Tue Aug 07, 2018 7:44 pm
If RPT doesn't already keep full circuit diagrams of each board and layouts with component identifications marked; may I suggest they do or questions like this are going to be almost impossible to answer with the passing of time.
... How would we be able to assemble boards if we didn't?
by jdb
Fri Aug 03, 2018 3:27 pm
Forum: General discussion
Topic: RPI 3B+ reports incorrect clockspeed. Video
Replies: 60
Views: 1621

Re: RPI 3B+ reports incorrect clockspeed. Video

I think this thread is done.

Also, refrain from calling other forum users "cancer". If you are unable make a point without throwing insults around, your time here will be short-lived.
by jdb
Fri Aug 03, 2018 2:35 pm
Forum: General discussion
Topic: RPI 3B+ reports incorrect clockspeed. Video
Replies: 60
Views: 1621

Re: RPI 3B+ reports incorrect clockspeed. Video

Don't copy-paste from other forums.

Yes, tkaiser is permabanned here for a) concern trolling b) ban evasion. Of course we can't ask other forums to remove misleading or plain incorrect information so copying it here is generally a bad idea.
by jdb
Fri Jul 27, 2018 3:21 pm
Forum: Advanced users
Topic: New RT (Real Time) kernel branch
Replies: 29
Views: 4529

Re: New RT (Real Time) kernel branch

If you're using a single thread to both read the sound samples and write the data out to disk, your program will block while the write completes. USB drives are by default written to in a synchronous manner (to help mitigate against surprise removal). You could try mounting the USB drive with the "a...
by jdb
Sat Jul 21, 2018 6:58 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Issues accessing GPIO register with single bytes
Replies: 7
Views: 349

Re: Issues accessing GPIO register with single bytes

Use a shim function call that does 32-bit read/write and packs/unpacks the results. This is exactly what happens with our bcm2835-sdhci driver - the upper level SD driver assumes 8-bit and 16-bit accesses work, so a set of shim functions are provided that translates any read/write cycle into a 32-bi...
by jdb
Tue Jul 10, 2018 3:19 pm
Forum: Advanced users
Topic: Speeding up boot process : RBP 3B+ and UBoot.
Replies: 3
Views: 320

Re: Speeding up boot process : RBP 3B+ and UBoot.

Turn off printing to the UART. U-boot is likely to be transmitting characters in polled mode, which at 115200bps will take a significant amount of time to output any substantial amount of text.
by jdb
Wed Jul 04, 2018 12:28 pm
Forum: Advanced users
Topic: How to output both left and right audio on a single PWM pin(18)?
Replies: 2
Views: 188

Re: How to output both left and right audio on a single PWM pin(18)?

If you open the VC ALSA driver with a format that has only 1 channel, the firmware should output "dual mono" (on both PWM outputs). You will have to downmix locally or use an ALSA plugin that does the downmix.
by jdb
Wed Jul 04, 2018 10:28 am
Forum: Advanced users
Topic: Analogue audio redux
Replies: 65
Views: 12469

Re: Analogue audio redux

It looks like tvjon's failing videos are also fixed with this update. There is however a bit of a limitation with these VPU-heavy codecs (VP8 in particular) - the vector unit is being contended between doing the video decode and the audio resampling, so you get underruns if someone is exclusively us...
by jdb
Tue Jul 03, 2018 2:17 pm
Forum: Advanced users
Topic: Analogue audio redux
Replies: 65
Views: 12469

Re: Analogue audio redux

Can people experiencing issues with stalled playback please try the latest rpi-update firmware?

There is a potential fix for this issue and a fix for the GPU crashing when certain high-stress workloads are used in conjunction with PWM audio.
by jdb
Mon Jul 02, 2018 3:17 pm
Forum: Advanced users
Topic: Analogue audio redux
Replies: 65
Views: 12469

Re: Analogue audio redux

Reported elsehwere: https://github.com/raspberrypi/linux/issues/2587 There's a bug in the VC4 firmware that results in writes to memory past end-of-buffer limits when you get repeated DMA underruns. There needs to be quite a lot of VPU activity to trigger this, particularly vector unit contention. T...
by jdb
Wed Jun 20, 2018 7:02 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Send 64 bit from one Raspberry PI 3 B to another
Replies: 30
Views: 1191

Re: Send 64 bit from one Raspberry PI 3 B to another

Absent any sensible reason why the UART, or SPI is unsuitable... Use a data pin and a strobe pin. The transmitter has an active-high strobe and asserts it for some period of time V over a total time T (where V < T, ideally V = 0.5T). It changes the value of the data pin when you command V to be de-a...
by jdb
Fri Jun 01, 2018 10:49 pm
Forum: General discussion
Topic: Raspberry Pi - export restrictions due to crypto?
Replies: 8
Views: 589

Re: Raspberry Pi - export restrictions due to crypto?

Read up on your computing history. The US of A designated advanced encryption algorithms as "munitions" in a futile attempt to stop the spread of strong encryption (that the NSA couldn't break) across the world. Turns out, people smart enough to implement asymmetric encryption are smart enough to wo...
by jdb
Thu May 31, 2018 6:16 pm
Forum: Advanced users
Topic: Analogue audio redux
Replies: 65
Views: 12469

Re: Analogue audio redux

OK that confirms the bug, then. Multi-stream "hardware" mixed playback (actually done on the VPU) is one of the target use-cases for the driver. The mixing is done at the same stage as the fractional rate conversion - we use an oddball internal samplerate (48828.125Hz) so that we can then use much c...
by jdb
Thu May 31, 2018 7:37 am
Forum: Advanced users
Topic: Analogue audio redux
Replies: 65
Views: 12469

Re: Analogue audio redux

Multiple audio streams should be supported. It was one of the reasons for rewriting the buffer handling code from the first version.

Do you get the same or different behaviour if you revert to the old driver (audio_pwm_mode=1)?
by jdb
Wed May 30, 2018 10:50 am
Forum: Advanced users
Topic: Isolated CPU Frequency measurement based on instructions?
Replies: 5
Views: 277

Re: Isolated CPU Frequency measurement based on instructions?

As a start, look at the disassembly listing of your inner loop. You will at minimum have a) two writes to the peripheral bus to toggle the GPIO b) an add instruction (more if you're operating on a uint64_t) c) a branch instruction This is going to end up running a lot slower than 1 add per cycle. It...
by jdb
Wed May 30, 2018 10:43 am
Forum: General discussion
Topic: HDMI sends frequency radiation
Replies: 3
Views: 246

Re: HDMI sends frequency radiation

The vast majority of cheap HDMI cables radiate bucketloads of RF. The HDMI spec calls for double-shielded cable where each individual differential pair is screened and the drain wire terminated on the dedicated ground return pin on the connector. The cable should then be overall screened and connect...
by jdb
Mon May 21, 2018 2:57 pm
Forum: General discussion
Topic: Keep Private Messaging function, please help and post
Replies: 21
Views: 808

Re: Keep Private Messaging function, please help and post

Locking. The reasons for removing the PM feature have been (re)stated ad nauseum.
by jdb
Mon May 21, 2018 1:54 pm
Forum: General discussion
Topic: Keep Private Messaging function, please help and post
Replies: 21
Views: 808

Re: Keep Private Messaging function, please help and post

Edited thread for readability (no gigantic blocks of text please).

Also, if this thread ends up being a continued rant by the OP, it's going to get locked.
by jdb
Mon May 21, 2018 1:47 pm
Forum: General discussion
Topic: Keep Private Messaging function, please help and post
Replies: 21
Views: 808

Re: Keep Private Messaging function, please help and post

I do think it's a somewhat stupid set of regulations...but the foundation have no choice here. More accurately, the regulations (especially COPPA) are ill-defined in some quite important aspects and it will take several test-cases (i.e. organisations getting sued or prosecuted) before the second-or...
by jdb
Thu May 10, 2018 12:45 pm
Forum: Advanced users
Topic: Mean of 60 temperature sensors
Replies: 17
Views: 860

Re: Mean of 60 temperature sensors

Read this: https://www.maximintegrated.com/en/app-notes/index.mvp/id/148 1-wire would be a recommended protocol because of the built-in unique serial number for each device. With many devices connected to a common bus or interface, you quickly run out of i2c addresses (as most sensors have maybe 3 a...
by jdb
Wed May 02, 2018 12:53 pm
Forum: Networking and servers
Topic: Connect more than eight USB drives?
Replies: 7
Views: 548

Re: Connect more than eight USB drives?

In general, devices are only polled when active (e.g. for WLAN adapters, if the interface is "up" but not necessarily associated with an AP) which implies a userspace client has opened the driver in question. If there are no mounted partitions then Linux should leave the mass storage device alone - ...
by jdb
Wed May 02, 2018 12:39 pm
Forum: Networking and servers
Topic: Connect more than eight USB drives?
Replies: 7
Views: 548

Re: Connect more than eight USB drives?

Someone in authority wrote: The maximum number of outstanding endpoint requests is 8. Mass storage devices will continually poll the IN endpoint for status requests (e.g. media removal, drive state) and will continually hog one of those slots. If you factor in the onboard devices (minimum 1 hub + t...
by jdb
Wed May 02, 2018 11:00 am
Forum: Networking and servers
Topic: Connect more than eight USB drives?
Replies: 7
Views: 548

Re: Connect more than eight USB drives?

There seems to be an inherent limitation as to how many USB drives one can connect to a Raspberry Pi. Yes, there is. If I connect more than eight drives the Raspi will drop more or less randomly one drive at bootup. Regardless of what kinds of hubs I connect whether one or two or more, regardless t...

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