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by jdb
Tue Jul 10, 2018 3:19 pm
Forum: Advanced users
Topic: Speeding up boot process : RBP 3B+ and UBoot.
Replies: 3
Views: 245

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: 155

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: 11700

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: 11700

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: 11700

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: 1085

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: 573

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: 11700

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: 11700

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: 263

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: 222

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: 752

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: 752

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: 752

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: 845

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: 481

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: 481

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: 481

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...
by jdb
Tue Apr 24, 2018 4:31 pm
Forum: General discussion
Topic: Industrial Reliability for 24/7 Use
Replies: 34
Views: 1672

Re: Industrial Reliability for 24/7 Use

Since you want to drag up ancient history, let me provide some context: I would not class having PCB errors as "pretty much never". There was the LAN chip miswiring which caused the LAN chip to run overy hot for some, Issue fixed in Pi Model B v2.0 and later (2012). LAN 1v8 net was miswired to the b...
by jdb
Tue Apr 24, 2018 9:55 am
Forum: Troubleshooting
Topic: Raspberry Pi 3 B+ lockups
Replies: 408
Views: 25046

Re: Raspberry Pi 3 B+ lockups

Thanks, (is that the scmoo plot that you plot out ?) My RAM was with reference to Jamesh's "I do wonder (guessing here) if it's down to the particular wafer that the SoC came from." . I asked as most seem to be asking for RAM 'slowing down' and just wondered. The Shmoo plot maps out the "stable are...
by jdb
Sat Apr 21, 2018 11:42 am
Forum: Troubleshooting
Topic: Raspberry Pi 3 B+ lockups
Replies: 408
Views: 25046

Re: Raspberry Pi 3 B+ lockups

Definitely the SoC and not the RAM? When we do qualification testing of a new piece of silicon, we make boards with split lots on. These are special SoCs that have been "skewed" in the semiconductor manufacturing process to emulate the maximum differences in performance/speed/power that you would g...
by jdb
Fri Apr 13, 2018 8:42 am
Forum: Advanced users
Topic: Raspberry Pi 3b+ and I2C to MXL7704 PMIC
Replies: 4
Views: 579

Re: Raspberry Pi 3b+ and I2C to MXL7704 PMIC

The VC4 firmware will periodically read from the PMIC in order to poll for the undervoltage flag. If you did try bitbashing the relevant GPIOs (the PMIC is not connected to any pins that map to the I2C peripheral) then the firmware would trample on your communication and you'd get nothing but nonsen...
by jdb
Fri Apr 06, 2018 3:56 pm
Forum: General discussion
Topic: New Raspberry Pi model 3B+ 1.4 GHz, 330Mbit Ethernet, 802.11ac, PoE
Replies: 376
Views: 34056

Re: New Raspberry Pi model 3B+ 1.4 GHz, 330Mbit Ethernet, 802.11ac, PoE

Unstickying as we are now 3 weeks post-launch.
by jdb
Thu Apr 05, 2018 9:33 pm
Forum: General discussion
Topic: RPi 3B+ gigabit ethernet bad download speeds.
Replies: 173
Views: 18588

Re: RPi 3B+ gigabit ethernet bad download speeds.

resiakt (tkaiser), In all honesty, your posts are becoming childishly tiresome and pointless. What good information you are adding to the thread is being outweighed by your obsession over nonexistent censorship. Please, give it a rest... -Robert This resiakt was yet another sockpuppet account, ther...
by jdb
Thu Apr 05, 2018 9:49 am
Forum: General discussion
Topic: First Post: What's the hole for in the Broadcom BCM2837B0 heat spreader?
Replies: 5
Views: 1610

Re: First Post: What's the hole for in the Broadcom BCM2837B0 heat spreader?

that "hole" indicates where ball a1 or pin 1 is. If it was required just for orientation, then it would be laser etched and not a hole. The hole is there to allow for venting when the SoC is being soldered on to the board. The thermal epoxy between the die and heatspreader may off-gas at 200C so a ...

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