Go to advanced search

by jdb
Fri Jun 01, 2018 10:49 pm
Forum: General discussion
Topic: Raspberry Pi - export restrictions due to crypto?
Replies: 8
Views: 501

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: 56
Views: 10442

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: 56
Views: 10442

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: 209

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: 196

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: 599

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: 599

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: 599

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: 770

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: 6
Views: 322

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: 6
Views: 322

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: 6
Views: 322

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: 1487

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: 374
Views: 21192

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: 374
Views: 21192

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: 487

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: 31935

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: 167
Views: 15303

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: 1491

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 ...
by jdb
Wed Mar 28, 2018 8:52 pm
Forum: General discussion
Topic: RPi 3B+ gigabit ethernet bad download speeds.
Replies: 167
Views: 15303

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

Wasn't me doing the banning this time... It was me. Said poster annoyed me sufficiently to motivate me to wield the banhammer with aplomb, so it was thusly wielded. Pro tip: even if you post technically useful information or analysis on our forums, if you act like you would be kicked out of a house...
by jdb
Tue Mar 20, 2018 12:42 pm
Forum: Advanced users
Topic: Analogue audio redux
Replies: 56
Views: 10442

Re: Analogue audio redux

Yes. Latest Raspbian enables this driver by default.
by jdb
Tue Mar 20, 2018 12:26 pm
Forum: Troubleshooting
Topic: 3V3 Power Rail and GPIO Reading 5.2V
Replies: 10
Views: 636

Re: 3V3 Power Rail and GPIO Reading 5.2V

As a final test, what are the switching nodes on the PAM2306 doing?

Measure the trace going between the switcher and the two SMT inductors with an oscilloscope - you should see switching at about ~1.7MHz.
by jdb
Tue Mar 20, 2018 12:21 pm
Forum: General discussion
Topic: New Raspberry Pi model 3B+ 1.4 GHz, 330Mbit Ethernet, 802.11ac, PoE
Replies: 376
Views: 31935

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

The silicon was mirrored and the top metal layers of the wafer were altered slightly. Bond pads (where wires would have connected) are turned into "bumps" that solder on to the chip substrate - the interposer that goes between the silicon and the PCB underneath. The top metal layers were modified to...
by jdb
Tue Mar 20, 2018 11:16 am
Forum: Troubleshooting
Topic: Stock Pi 3 B+ in chilly UK Temperature Icon :(
Replies: 12
Views: 762

Re: Stock Pi 3 B+ in chilly UK Temperature Icon :(

My 3B+ has settled at 62.3C running your "yes" stress test (in the UK with snow outside). It does have a small heat sink. Try this, it uses NEON ..... wget https://raw.githubusercontent.com/ssvb/cpuburn-arm/master/cpuburn-a53.S gcc -o cpuburn-a53 cpuburn-a53.S ./cpuburn-a53 CPUburn is a pathologica...
by jdb
Tue Mar 20, 2018 11:12 am
Forum: Advanced users
Topic: Analogue audio redux
Replies: 56
Views: 10442

Re: Analogue audio redux

The buffer driving the audio is the same on all models of Pi since B+. The original Model B/A used a noisier arrangement and Zero doesn't have analogue audio output circuitry.

Go to advanced search