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by jdb
Thu Nov 25, 2021 5:09 pm
Forum: General discussion
Topic: Unable to find Raspberry Pi 4B for sale anywhere. Why?
Replies: 32
Views: 1003

Re: Unable to find Raspberry Pi 4B for sale anywhere. Why?

MikeDB wrote:
Wed Nov 24, 2021 11:15 pm
Unless RPT substituted a slower RAM, which is unlikely unless there was a world shortage (ah :-))
The opposite is the case for DRAM. DRAM fabs are different technology to $random_asic fabs and as such there's a glut of DRAM now.
by jdb
Mon Nov 22, 2021 4:02 pm
Forum: General discussion
Topic: The crystal oscillator of Pi 4B
Replies: 16
Views: 576

Re: The crystal oscillator of Pi 4B

You will need to use PPS input (from a GPS time source) to correct for temperature and aging of the Pi's main crystal oscillator. There are many guides on how to set up PPSD on a Pi. If you don't want to use a whole GPS receiver, then you can use a TCXO-derived RTC in place of the GPS and accept a s...
by jdb
Sat Nov 13, 2021 5:13 pm
Forum: General discussion
Topic: are the single core pi's invulnerable to spectre and meltdown?
Replies: 4
Views: 285

Re: are the single core pi's invulnerable to spectre and meltdown?

Pi 4 is vulnerable (and mitigations are in place) but Pi 0-3 are not. Note that the spectre and meltdown vulnerabilities are not a function of how many cores there are in a system, they depend on specific microarchitectural features. The ARM1176/A7/A53 cores are all in-order execution which eliminat...
by jdb
Fri Nov 12, 2021 7:58 pm
Forum: General discussion
Topic: RPI 4B SD-Card speed
Replies: 5
Views: 308

Re: RPI 4B SD-Card speed

Hello I was wondering how fast the SD card port was on the pi. Not the SD card, but the SD Card port. It is twice as fast on the Pi4 compared to previous models. Which is still not an absolute value... The Pi 4 SD card slot supports UHS-1 DDR50. That is, 50MB/s less overheads. Previous models (and ...
by jdb
Thu Nov 11, 2021 8:11 pm
Forum: Off topic discussion
Topic: Pi4 availability
Replies: 14
Views: 657

Re: Pi4 availability

rpdom wrote:
Thu Nov 11, 2021 7:38 pm
Ebentaal?
sensible_chuckle.gif
by jdb
Wed Nov 10, 2021 8:46 pm
Forum: Advanced users
Topic: Bullseye ssh host keys
Replies: 21
Views: 750

Re: Bullseye ssh host keys

So I don't trust these keys, you can't proof the oposite. End of discussion. :-) I generate fresh keys on my raspis after installing fresh OS (and always when cloning cards for more raspis). Nobody is stopping you from doing so. For everyone else, Raspberry Pi OS offers a reasonable guarantee that ...
by jdb
Wed Nov 10, 2021 10:59 am
Forum: Advanced users
Topic: Bullseye ssh host keys
Replies: 21
Views: 750

Re: Bullseye ssh host keys

The hwrng generates provably random data at 70K _bytes_ per second. You have more entropy than you could ever need to generate an RSA elliptic-curve key before systemd even starts the ssh keygen process.

Edit: and for the avoidance of doubt, rngd is present and starts at boot.
by jdb
Wed Nov 10, 2021 8:14 am
Forum: Advanced users
Topic: Bullseye ssh host keys
Replies: 21
Views: 750

Re: Bullseye ssh host keys

pi-anazazi wrote:
Wed Nov 10, 2021 8:11 am
To me the question is: If the keys are generated THAT early during boot (no time/date yet), how much entropy is at that time in the system?
A lot, because the CRNG is seeded with per-boot entropy provided by the hardware random number generator.
by jdb
Wed Nov 10, 2021 8:04 am
Forum: Troubleshooting
Topic: USB Keyoard Dongle Error "usbhid 1-1.3:1.1: couldn't find an input interrupt endpoint"
Replies: 1
Views: 102

Re: USB Keyoard Dongle Error "usbhid 1-1.3:1.1: couldn't find an input interrupt endpoint"

The broken descriptors are a property of the device, not the operating system. Has the keyboard dongle ever worked?
by jdb
Wed Nov 10, 2021 8:02 am
Forum: Advanced users
Topic: Bullseye ssh host keys
Replies: 21
Views: 750

Re: Bullseye ssh host keys

Milliways wrote:
Wed Nov 10, 2021 6:21 am

Including the date in fake-rtc file in the image is also an error, although trivial.
Why is this an error?

Should the system instead boot first with a date of Jan 1 1970?
by jdb
Tue Nov 02, 2021 3:28 pm
Forum: General
Topic: Picking the brains of PIO experts
Replies: 25
Views: 1003

Re: Picking the brains of PIO experts

If only the PLL post-dividers had phase nudge :(
by jdb
Thu Oct 28, 2021 2:51 pm
Forum: General discussion
Topic: The Raspberry Pi Zero 2 W Thread
Replies: 378
Views: 18816

Re: The Raspberry Pi Zero 2 W Thread

From my PoV, I think the most interesting thing about this board is that it's an armv8-A-capable chip. That should allow for people to migrate off the 32b PiOS as and when that becomes too unwieldy to support in, say, five years' time or so... Impressive job. Very well done. Correctamundo - with ze...
by jdb
Thu Oct 28, 2021 12:39 pm
Forum: SDK
Topic: How many adc_read()s maximally in 1 second?
Replies: 6
Views: 386

Re: How many adc_read()s maximally in 1 second?

For frequency domain measurements, you can actually use the ADC to subsample 250Khz of bandwidth up to about 30MHz (after which the analogue pads parallel-bonded digital pads and input mux start to attenuate the input). You just have to be careful to pick one of the positive frequency images not neg...
by jdb
Thu Oct 28, 2021 7:51 am
Forum: General discussion
Topic: The Raspberry Pi Zero 2 W Thread
Replies: 378
Views: 18816

Re: The Raspberry Pi Zero 2 W Thread

If I'm honest... I was hoping for better. I think the quad-core CPU is a great addition, but the lowered clock speed really hurts the performance, and only 512MB RAM is quite disappointing considering how that amount of RAM is barely usable nowadays. I was kinda hoping for at least 1GB RAM. If we c...
by jdb
Sun Oct 10, 2021 7:56 pm
Forum: General discussion
Topic: About the New Raspberry Pi 4b cpu revision
Replies: 69
Views: 3733

Re: About the New Raspberry Pi 4b cpu revision

In theory, once a given product goes out of stock and is then replenished, all new packages should be the newest variant. In practice...not so much. I am confident there are no-pre USB fix devices left out there waiting to be sold. Pi4 products sell very quickly, every one we make gets sold pretty ...
by jdb
Tue Oct 05, 2021 8:27 pm
Forum: General discussion
Topic: Astro Pi - the original, not the Mk II hardware.
Replies: 7
Views: 464

Re: Astro Pi - the original, not the Mk II hardware.

Trying to get a Raspberry Pi 3(B+) is tricky now, although they are still available. The original Astro Pis were Pi2B (v1.1, IIRC). No, they were Pi 1 B+. Pi 2 was released after the astro-pi hardware design was already in progress so in order to hit the Dec 2015 launch (to conicide with Tim Peake'...
by jdb
Thu Sep 30, 2021 8:34 pm
Forum: General
Topic: LCSC/JLCPCB have marked the RP2040 as discontinued
Replies: 26
Views: 1409

Re: LCSC/JLCPCB have marked the RP2040 as discontinued

dshadoff wrote:
Thu Sep 30, 2021 8:24 pm
kilograham wrote:
Thu Sep 30, 2021 3:03 pm
Note that B2 chip revision actually also fixes USB h/w issues RP2040-E2 and E5
This is good news. Where can I find out more about the nature of those USB h/w issues ?
Read the errata section in the RP2040 datasheet.
by jdb
Wed Sep 22, 2021 9:37 am
Forum: General discussion
Topic: Raspberry Pi as a PCIe endpoint
Replies: 2
Views: 259

Re: Raspberry Pi as a PCIe endpoint

None of them. The BCM2711 SoC as used in Compute Module 4 and Raspberry Pi 4 only supports RC (root complex) mode of operation.
by jdb
Tue Sep 21, 2021 12:35 pm
Forum: Compute Module
Topic: Nvme and asm1164e
Replies: 7
Views: 489

Re: Nvme and asm1164e

The PCIe RC driver allocates MSIs from a bitmap, which selects 2^N aligned chunks of length 2^N. Requesting 5 interrupts will allocate 8 internally, which explains why it goes splat with 5 drives not 4. However - running out of PCIe resources should not be fatal (and implies a bug somewhere). Edit ...
by jdb
Mon Sep 20, 2021 6:19 pm
Forum: Off topic discussion
Topic: "We're in the money"
Replies: 5
Views: 1022

Re: "We're in the money"

As is often the case, the article conflates the charitable RPF with its RPT commercial arm - Is there an official press release or similar which clarifies what it all means ? I couldn't find anything on the blog. The cityAM piece is a bit mangled, but the original Telegraph article (published both ...
by jdb
Mon Sep 20, 2021 4:11 pm
Forum: General discussion
Topic: How to set Parity as Odd in Raspberry Pi OS to solve 'messy code' issue in USB serial console when booting
Replies: 8
Views: 481

Re: How to set Parity as Odd in Raspberry Pi OS to solve 'messy code' issue in USB serial console when booting

Hmm it seems there is a limitation in agetty (the default serial console spawner) that means you can't use 8-bit serial with parity. agetty can however use 7-bit with odd parity. I would recommend turning off the serial console entirely by removing the console=serial0 parameter and running your app...
by jdb
Mon Sep 20, 2021 11:59 am
Forum: General discussion
Topic: How to set Parity as Odd in Raspberry Pi OS to solve 'messy code' issue in USB serial console when booting
Replies: 8
Views: 481

Re: How to set Parity as Odd in Raspberry Pi OS to solve 'messy code' issue in USB serial console when booting

Hmm it seems there is a limitation in agetty (the default serial console spawner) that means you can't use 8-bit serial with parity. agetty can however use 7-bit with odd parity. I would recommend turning off the serial console entirely by removing the console=serial0 parameter and running your appl...
by jdb
Mon Sep 20, 2021 11:45 am
Forum: General discussion
Topic: How to set Parity as Odd in Raspberry Pi OS to solve 'messy code' issue in USB serial console when booting
Replies: 8
Views: 481

Re: How to set Parity as Odd in Raspberry Pi OS to solve 'messy code' issue in USB serial console when booting

Modify the parameter console=serial0,115200 to console=serial0,115200o8 to set the boot console parity. See: https://www.kernel.org/doc/html/latest/ ... nsole.html

Edit: you will also need to change the defaults for systemd's serial console widget.
by jdb
Fri Sep 17, 2021 8:57 pm
Forum: General discussion
Topic: Feature request for the RPi 5 - Browser that uses hw well to play YouTube! :)
Replies: 8
Views: 525

Re: Feature request for the RPi 5 - Browser that uses hw well to play YouTube! :)

You should direct your complaints to Google. I'm sure you'll get more traction than we have.
by jdb
Thu Sep 16, 2021 6:50 pm
Forum: General discussion
Topic: New ISS Pi in space, Pi4, new SenseHAT, HD camera, Corel and extra.
Replies: 21
Views: 1727

Re: New ISS Pi in space, Pi4, new SenseHAT, HD camera, Corel and extra.

Will the v2 HAT be available to buy anywhere anytime soon, or is this just a two-off for the ISS? -- Mike Is it actually a new Sense Hat? Or just two more sensors added separately? I watched the video, but I'm still not sure which it is? It's a v2 HAT. Added sensors plus the annoying bug with Pi4 t...

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