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by jdb
Thu Jun 13, 2019 1:00 pm
Forum: Compute Module
Topic: USB 2.0 Dropped frames
Replies: 13
Views: 791

Re: USB 2.0 Dropped frames

Noted about I2S - while the peripheral can be driven in slave mode (from an external clock), and can be driven at high bitrates, the required rate is likely too fast for most other I2S interfaces. There is a possibility that I can slightly mangle isochronous scheduling. For a sequence of isochronous...
by jdb
Tue Jun 11, 2019 4:06 pm
Forum: Compute Module
Topic: USB 2.0 Dropped frames
Replies: 13
Views: 791

Re: USB 2.0 Dropped frames

The USB hardware supports DMA transfers at the granularity of a single USB transfer. There is no support for chaining transfers together, so each USB transfer results in a interrupt to the CPU which must be handled by software. The only exception to this is high-speed bulk, where the core can transf...
by jdb
Tue Jun 11, 2019 1:23 pm
Forum: Compute Module
Topic: USB 2.0 Dropped frames
Replies: 13
Views: 791

Re: USB 2.0 Dropped frames

USB2.0 isochronous suffers from a subset of the issues that beset full-speed isochronous split transactions. Typically USB1.1 isochronous transfers are scheduled every full-speed frame and must complete within that frame or the hub will drop the transfer (or response data). This means that the host ...
by jdb
Fri May 31, 2019 10:17 am
Forum: General discussion
Topic: RISC-V
Replies: 135
Views: 7643

Re: RISC-V

Not just a memory controller - you need a SDRAM PHY of substantial complexity to talk to anything more complicated than PC133 SDRAM - DDR2 and onwards needs complicated lane deskew and impedance compensation. This part of the interface ends up being almost pure analogue logic and so far the "open so...
by jdb
Fri May 31, 2019 9:38 am
Forum: General discussion
Topic: Is there a way to reset the status returned by vcgencmd get_throttled?
Replies: 10
Views: 248

Re: Is there a way to reset the status returned by vcgencmd get_throttled?

Actually, the argument passed to get_throttled changes the variable returned, and acts as a bitmask to reset the additional variable. There are two sets of sticky bits, permanent and recent. a) get_throttled with no arguments returns permanent sticky bits in the top 16 bits - these are never reset. ...
by jdb
Fri May 24, 2019 1:28 pm
Forum: General discussion
Topic: Best solder sucker on Amazon?
Replies: 15
Views: 972

Re: Best solder sucker on Amazon?

I use a Miller Flexivac 2009, but the 2006 is cheaper as it's all plastic
http://www.farnell.com/datasheets/1701825.pdf

Protip: "antistatic" in the name usually means "double the price". But most professional-level tools are antistatic.
by jdb
Thu May 23, 2019 7:10 pm
Forum: General discussion
Topic: Best solder sucker on Amazon?
Replies: 15
Views: 972

Re: Best solder sucker on Amazon?

The solder sucker I currently use (I have tried a few different ones) has a flexible silicone pipe for the nozzle. Because it is soft it doesn't transfer the force of the pump onto the component that is being desoldered. It comes with a couple of pieces of the silicone tube that can be cut to lengt...
by jdb
Wed May 22, 2019 10:16 pm
Forum: Off topic discussion
Topic: ARM, Broadcom pull the plug on Huawei
Replies: 14
Views: 1247

Re: ARM, Broadcom pull the plug on Huawei

W. H. Heydt wrote:
Wed May 22, 2019 10:11 pm
The whole situation is political. No way to get around *that*.
In that case, this thread is done-zo.
by jdb
Wed May 22, 2019 9:21 pm
Forum: Off topic discussion
Topic: ARM, Broadcom pull the plug on Huawei
Replies: 14
Views: 1247

Re: ARM, Broadcom pull the plug on Huawei

Please limit your discussions to people outside the White House (and, on balance, people outside the Central Committee of the Chinese Communist Party). This thread is Off-Topic, but technology-related. Politics threads get deleted quickly.
by jdb
Mon May 20, 2019 3:41 pm
Forum: Off topic discussion
Topic: Raspberry Pi with Usb3 as Southbridge
Replies: 4
Views: 887

Re: Raspberry Pi with Usb3 as Southbridge

Closing, as we've reached the weekly limit for "Raspberry Pi N+1 should have feature X" posts.
by jdb
Fri May 17, 2019 9:18 am
Forum: Compute Module
Topic: USB 2.0 Dropped frames
Replies: 13
Views: 791

Re: USB 2.0 Dropped frames

Please post
- the full output of dmesg after playback has started and you've had at least one corrupt audio frame
- the output of lsusb -v and lsusb -t
by jdb
Thu May 16, 2019 7:29 pm
Forum: Off topic discussion
Topic: is the pi worth it?
Replies: 103
Views: 6092

Re: is the pi worth it?

Every connector on the Pi is a hotpluggable connector - with the exception of GPIO, but with care these pins are hotpluggable with jumper wires (but not HATs). I've heard of people damaging their Pi trying to hot plug the camera connector. For the record and for those who might otherwise try, is it...
by jdb
Thu May 16, 2019 6:28 pm
Forum: Off topic discussion
Topic: is the pi worth it?
Replies: 103
Views: 6092

Re: is the pi worth it?

Using m.2 instead of USB3 sounds a bit like when IBM replaced the reverse-compatible AT bus with micro-channel. C There is no reverse engineering with pcie, its native "PCI Express (PCIe) is the de-facto chip-to-chip connectivity standard for a wide range of applications from high-performance CPUs,...
by jdb
Sun May 12, 2019 12:57 pm
Forum: Troubleshooting
Topic: Don't try this at home, kids!
Replies: 11
Views: 521

Re: Don't try this at home, kids!

That suggests the PMIC is working, at least well enough to turn on 3V3 and other supplies the S0C needs to come out of reset and run its firmware, then the SoC fails to communicate with the PMIC so shuts itself down. But that doesn't seem to explain why the 3V3 isn't present on boards which have be...
by jdb
Tue May 07, 2019 3:29 pm
Forum: Advanced users
Topic: Moving Linux kernel to 4.19
Replies: 232
Views: 62588

Re: Moving Linux kernel to 4.19

Github was giving me a whole 300kib/second when cloning today - I would guess they are having internal issues.
by jdb
Fri Apr 26, 2019 4:38 pm
Forum: Troubleshooting
Topic: I let the smoke out with 24volt into 3B+
Replies: 12
Views: 525

Re: I let the smoke out with 24volt into 3B+

Look at it this way. As the overvoltage clamp diode did its job and then stopped doing it (due to no longer being in possession of its magic smoke), 24V ended up being applied to the board with no overvoltage clamp. I think you need to buy a new Pi. Edit: wait, the component on the *underside* of th...
by jdb
Fri Apr 12, 2019 3:32 pm
Forum: Off topic discussion
Topic: I know this sounds like something from a Spy novel or makes me sound a like a crazy person but...
Replies: 26
Views: 1233

Re: I know this sounds like something from a Spy novel or makes me sound a like a crazy person but...

If you want to get even more paranoid, note that every reasonably complex ASIC has silicon debug capable of reading out the entire state of the chip (for production test). https://hal-lirmm.ccsd.cnrs.fr/lirmm-00599690/document It's a potential attack vector for e.g. reading out your AES key but if y...
by jdb
Wed Apr 10, 2019 12:03 pm
Forum: Compute Module
Topic: I got thermal paste on my board
Replies: 7
Views: 367

Re: I got thermal paste on my board

Denatured alcohol is *not* isopropanol/isopropyl alcohol. In the UK at least, it's ethanol mixed with methanol, a far more aggressive solvent than isopropyl alcohol. Isopropyl alcohol is generally safe to use on PCBs to clean off gunk.
by jdb
Tue Apr 02, 2019 6:53 pm
Forum: Advanced users
Topic: Voltage reduction under thermal throttling
Replies: 7
Views: 402

Re: Voltage reduction under thermal throttling

There are three voltage/frequency setpoints for the 3B+ 1.2V @ 600MHz - when idle or throttled due to 5V undervoltage or due to exceeding the 85C temp limit "turbo" volts @ 1200MHz - when the temperature is above the soft temp limit and below the 85C temp limit. ARM frequency gets progressively ramp...
by jdb
Sat Mar 30, 2019 12:05 am
Forum: The MagPi
Topic: Issue 80 : Pi FM Transmitter
Replies: 7
Views: 1132

Re: Issue 80 : Pi FM Transmitter

Thanks for bringing this to our attention.
by jdb
Fri Mar 29, 2019 7:29 pm
Forum: General discussion
Topic: Pi 4 questions
Replies: 166
Views: 7995

Re: Pi 4 questions

Core memory came back for Arduino chips a few years ago http://corememoryshield.com it’s not a bad price either £30 approx for 32 bits of memory. So so tempting :lol: Given modern ADC resolutions and speed, I wonder if you can't store more than 1 bit per ferrite. The principle of core memory relies...
by jdb
Fri Mar 29, 2019 12:43 pm
Forum: General discussion
Topic: Pi 4 questions
Replies: 166
Views: 7995

Re: Pi 4 questions

The problem with going for even smaller and smaller processes is that the smaller ones are REALLY EXPENSIVE. You will have noted that the prime selling point of the Pi is cost performance ratio. So we really are not interested in using the latesst technology, simply because its too expensive. So wh...
by jdb
Thu Mar 28, 2019 7:34 pm
Forum: General discussion
Topic: Pi 4 questions
Replies: 166
Views: 7995

Re: Pi 4 questions

I come here, I feel old. I visit the in-laws (91 & 92), I feel young. She complains about just about everything, so I tell her she's still got the Queen's telegram to look forward to. I doubt Charles will still be doing telegrams by the time I'm due for one, but I tell myself at least I've got the ...
by jdb
Thu Mar 28, 2019 4:33 pm
Forum: General discussion
Topic: Pi 4 questions
Replies: 166
Views: 7995

Re: Pi 4 questions

jbudd wrote:
Thu Mar 28, 2019 1:16 pm
Pushing slightly at the door marked "Secret" jamesh, do you have a working prototype on your desk yet?
no
by jdb
Fri Mar 22, 2019 9:21 pm
Forum: Automation, sensing and robotics
Topic: electric dog collar based on radio waves
Replies: 13
Views: 463

Re: electric dog collar based on radio waves

Thank You guys for all the help , I'm almost finished the normal fence to them2400metres squares to give them freedom , but if You are not up to make my idea on raspberry IT gave me a brighter look on this problem. Thanks, If somebody Has some idea please do not hesitate Do not use Raspberry Pis to...

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