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by jdb
Fri Oct 12, 2018 1:44 pm
Forum: General discussion
Topic: A2 app performance class SD cards
Replies: 10
Views: 350

Re: A2 app performance class SD cards

+1 for App-class cards. The A1 random-read performance was often 2-3x our recommended NOOBS cards, but with a price premium.
A2 looks like a welcome bump to the critical parameter - random read IOPS.
by jdb
Thu Sep 20, 2018 5:29 pm
Forum: Troubleshooting
Topic: The USB power appeal
Replies: 43
Views: 1602

Re: The USB power appeal

Thousands of the RPi users are forced to do silly workarounds like this: https://i.stack.imgur.com/j7WBo.jpg to have their RPis working. Please provide evidence to support the claim that "thousands" of Raspberry Pi users have had to modify their boards. Also, what are the symptoms of the alleged is...
by jdb
Wed Sep 19, 2018 7:29 pm
Forum: General discussion
Topic: CB beacon out of raspberry pi
Replies: 9
Views: 359

Re: CB beacon out of raspberry pi

CB does not require license and i must prove you wrong RPi CAN BE USED as radio transmitter and i have passive filters And how will you ensure that the "passive filters" sufficiently filter harmonic emissions? Are you going to test your modified Pi in an anechoic chamber to make sure it won't leak ...
by jdb
Tue Sep 11, 2018 9:37 pm
Forum: Add-ons
Topic: PoE HAT - USB Ports not working - over-current
Replies: 213
Views: 16608

Re: PoE HAT - USB Ports not working - over-current

Thanks for interesting answers, tests and debate regarding power between the 2 sources. About the original issue of the PoE HAT, the engineering suggest some RPI 3B+ hardware are not impacted: one of the two brands of USB current limiting switch -> Is it possible to identify the component (software...
by jdb
Wed Sep 05, 2018 7:40 pm
Forum: Add-ons
Topic: PoE HAT - USB Ports not working - over-current
Replies: 213
Views: 16608

Re: PoE HAT - USB Ports not working - over-current

Please note: modifying your PoE HAT will obviously invalidate any warranty claim. It is however very useful that people are experimenting as it gives us more information to work with. We have managed to replicate the issue in a controlled environment (i.e. in the lab with programmable loads on the U...
by jdb
Tue Sep 04, 2018 10:34 pm
Forum: Add-ons
Topic: PoE HAT - USB Ports not working - over-current
Replies: 213
Views: 16608

Re: PoE HAT - USB Ports not working - over-current

If it doesn't work without a fudge then it's more expensive but more of a fudge than a cheap POE splitter, I wanted it as a neater alternative but as it's now turned out to have significant disadvantages over a POE splitter and no real advantages, I can't see any reason to keep it or recommend it. ...
by jdb
Tue Sep 04, 2018 9:25 pm
Forum: Add-ons
Topic: PoE HAT - USB Ports not working - over-current
Replies: 213
Views: 16608

Re: PoE HAT - USB Ports not working - over-current

Personally I don't regard this as a fix, so will be sending my hats back as faulty for a refund when I get back from this work trip and will go back to using cheap splitters at a fraction of the price but without the reliability problems. I'm surprised something this bad got released. Surely, the i...
by jdb
Wed Aug 29, 2018 12:15 pm
Forum: Advanced users
Topic: Why is the L2 cache disabled by default?
Replies: 4
Views: 311

Re: Why is the L2 cache disabled by default?

The parameter you are referring to controls whether ARM memory accesses are routed via the L2 (cached) bus or uncached bus that goes straight to RAM. BCM2836 and BCM2837 both have dedicated L2 caches for the ARM complex therefore using the GPU L2 cache will a) swamp the cache with ARM L2 line evicti...
by jdb
Sat Aug 11, 2018 8:58 pm
Forum: Advanced users
Topic: dtoverlay=dht11?
Replies: 4
Views: 196

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: 1365

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: 1155

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: 2151

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: 2151

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: 31
Views: 5716

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: 400

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: 363

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: 221

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: 13869

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: 13869

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: 13869

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: 1309

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: 653

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: 13869

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: 13869

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: 313

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...

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