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by cleverca22
Tue Mar 31, 2020 8:03 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: What is the beast way to generate a clock signal?
Replies: 1
Views: 33

Re: What is the beast way to generate a clock signal?

i think you want to use the normal SPI controller for its clock and data lines

the clock signal needs to be aligned to when you sample the data line, and the SPI hardware can do that for you
by cleverca22
Mon Mar 30, 2020 9:34 pm
Forum: Compute Module
Topic: Supported DPI Output Resolutions
Replies: 14
Views: 4089

Re: Supported DPI Output Resolutions

yeah, i think that 4v might be resonance/ringing, due to the length of the lines i'm using, and due to having so few samples, i cant measure it well the only thing i can add, is that both images where captured in repetitive store mode, so it was taking many samples, at slight offsets, to make up for...
by cleverca22
Sun Mar 29, 2020 10:12 pm
Forum: Troubleshooting
Topic: Rasperry Pi 4 localhost connection refused
Replies: 8
Views: 150

Re: Rasperry Pi 4 localhost connection refused

what does `netstat -anp | grep 4840` show?
by cleverca22
Sun Mar 29, 2020 10:08 pm
Forum: General discussion
Topic: From Pi to Google Cloud Print device
Replies: 5
Views: 146

Re: From Pi to Google Cloud Print device

https://killedbygoogle.com/

of note, it looks like google plans to kill off cloud printing in about 9 months (end of this year), so you may want to find another solution instead
by cleverca22
Sun Mar 29, 2020 6:05 am
Forum: Compute Module
Topic: Supported DPI Output Resolutions
Replies: 14
Views: 4089

Re: Supported DPI Output Resolutions

The GPIOs are not rated above 75MHz so getting 120MHz is very surprising have those limits changed on the rpi4? i'm able to bit-bang a 125mhz signal, though it has extremely obvious problems reaching the rails, and my scope is only rated for 100mhz, so its surprising that i can even measure this ht...
by cleverca22
Sat Mar 28, 2020 6:56 pm
Forum: General discussion
Topic: Raspberry Pi 4 usb boot?
Replies: 559
Views: 179218

Re: Raspberry Pi 4 usb boot?

According to the firmware changelog there seems to be change for the so far unannounced Compute Module 4 regarding USB-booting: firmware: USB device boot for CM4 https://github.com/raspberrypi/firmware/commit/5574077183389cd4c65077ba18b59144ed6ccd6d#diff-881cc4157ed641a365a86452f27ed745 So getting ...
by cleverca22
Sat Mar 28, 2020 6:48 pm
Forum: Bare metal, Assembly language
Topic: Using the system timer interrupt at 1MHz
Replies: 14
Views: 700

Re: Using the system timer interrupt at 1MHz

all 4 timers are shared between the vpu and arm, so you need to first figure out which timers the firmware and linux are using the baremetal arm examples wont take the ones linux is using into account, but a simple way to check, is to just read the 4 compare registers a few times, and see if they ar...
by cleverca22
Sat Mar 28, 2020 4:30 am
Forum: Bare metal, Assembly language
Topic: Using the system timer interrupt at 1MHz
Replies: 14
Views: 700

Re: Using the system timer interrupt at 1MHz

https://github.com/librerpi/rpi-open-firmware/blob/master/firmware/interrupt.c#L37-L40 on the VPU side, the IRQ vector table is an array of 128 function pointers slots 64-127 are the 64 IRQ's that are described in the official docs, but without the whole matrix mess 278 #define INTERRUPT_TIMER0 (INT...
by cleverca22
Wed Mar 25, 2020 5:44 pm
Forum: Advanced users
Topic: Destroy pi sd card... On purpose if removed
Replies: 53
Views: 1478

Re: Destroy pi sd card... On purpose if removed

Secure Boot is broadly worthless anyway, because of the problem mentioned above: it requires the *entire stack*[0] to be secure: firmware, bootloader, kernel[1], *anything which may be executed as root*[0] (or equivalent), and anything which can be influenced to execute anything as root. [0] FFS......
by cleverca22
Tue Mar 24, 2020 10:37 pm
Forum: Advanced users
Topic: Destroy pi sd card... On purpose if removed
Replies: 53
Views: 1478

Re: Destroy pi sd card... On purpose if removed

it would be far simpler to just patch the program to not check the serial# and if your using encryption with the serial# as the key, just read the serial# with a different distro, and decrypt it the ideas i gave, stop them from even knowing the serial#, so they cant do either of the above So, we ag...
by cleverca22
Tue Mar 24, 2020 7:32 pm
Forum: Advanced users
Topic: Destroy pi sd card... On purpose if removed
Replies: 53
Views: 1478

Re: Destroy pi sd card... On purpose if removed

it would be far simpler to just patch the program to not check the serial#

and if your using encryption with the serial# as the key, just read the serial# with a different distro, and decrypt it

the ideas i gave, stop them from even knowing the serial#, so they cant do either of the above
by cleverca22
Tue Mar 24, 2020 6:56 pm
Forum: Advanced users
Topic: Does the Pi support booting from GPT drives?
Replies: 26
Views: 1921

Re: Does the Pi support booting from GPT drives?

of note, the rpi4 loads the `bootcode.bin` stage from SPI flash, so it could potentially be upgraded to support finding `start4.elf` on a GPT partitioned anything but, if the mask-rom doesnt support GPT, you have no way to use `recovery.bin` for re-flashing/upgrading/unbricking, which could be a pro...
by cleverca22
Tue Mar 24, 2020 6:16 pm
Forum: Bare metal, Assembly language
Topic: Using the system timer interrupt at 1MHz
Replies: 14
Views: 700

Re: Using the system timer interrupt at 1MHz

it would be a bit more complicated, and well into undocumented territory, but the VPU side of the rpi has a full IRQ vector table, and all 4 timer channels have their own irq vector, no sharing in theory, you could take one of the timer channels the VPU never uses, and then use it for a custom VPU i...
by cleverca22
Tue Mar 24, 2020 5:48 pm
Forum: Troubleshooting
Topic: Pi4b with USB-C Port Hardware Damage is not working anymore.
Replies: 1
Views: 87

Re: Pi4b with USB-C Port Hardware Damage is not working anymore.

When I put no SD Card in and power the Pi over the GPIO with 5.2V, I get a red LED and a flashing green LED. When I put a SD Card in, I get the same result. if its 4 flashes, i think that means `start4.elf` isnt found that implies that the VPU and SPI-eeprom are fully functioning, and its booting t...
by cleverca22
Tue Mar 24, 2020 5:27 pm
Forum: Advanced users
Topic: Destroy pi sd card... On purpose if removed
Replies: 53
Views: 1478

Re: Destroy pi sd card... On purpose if removed

if you put a custom signing key into the OTP, then only firmware you approve of (which you signed) can boot on the pi Are you saying that standard Pi firmware does this already, or is this custom firmware that will only boot a custom kernel? currently, the official rpi firmware doesnt support secur...
by cleverca22
Tue Mar 24, 2020 2:37 am
Forum: Advanced users
Topic: Destroy pi sd card... On purpose if removed
Replies: 53
Views: 1478

Re: Destroy pi sd card... On purpose if removed

for the 1st point, you would need to convince whoever is fabbing the RPI board, to not program the signing key in the OTP memory, so you have the ability to put your own key onto it (and double-check if its blank or not first, before bothering them) If this was available what stops someone else get...
by cleverca22
Mon Mar 23, 2020 7:15 pm
Forum: General discussion
Topic: Am I being Hacked?? (Strange sting in history)
Replies: 23
Views: 961

Re: Am I being Hacked?? (Strange sting in history)

[email protected]:/$ md5sum --check /var/lib/dpkg/info/git.md5sums etc/bash_completion.d/git-prompt: OK usr/bin/git: OK usr/bin/git-shell: OK usr/bin/git-upload-pack: OK usr/lib/git-core/git-p4: OK any APT based system will maintain a list of md5 hashes for every file it installs you can then just `cd /` and...
by cleverca22
Mon Mar 23, 2020 3:49 pm
Forum: Advanced users
Topic: Destroy pi sd card... On purpose if removed
Replies: 53
Views: 1478

Re: Destroy pi sd card... On purpose if removed

in the end: this relies on a custom signing key (may require ordering an un-burned rpi from the foundation) the foundation adding support for bootcode.bin to check start.elf signatures the foundation adding start.elf support for checking signatures on other files in /boot/ I asked about this before...
by cleverca22
Mon Mar 23, 2020 1:38 pm
Forum: Advanced users
Topic: Destroy pi sd card... On purpose if removed
Replies: 53
Views: 1478

Re: Destroy pi sd card... On purpose if removed

something that would need some support from the rpi foundation (the open firmware likely cant meet your needs yet) for the rpi 1-3 line, its capable of checking a signature on `bootcode.bin` but that is disabled by default (i dont know if the key is burnt into OTP yet) in theory, you could burn a cu...
by cleverca22
Fri Mar 20, 2020 11:19 am
Forum: Troubleshooting
Topic: wrong OTP for pi4?
Replies: 6
Views: 222

Re: wrong OTP for pi4?

the only thing the OTP really does on a 4, is control its ability to boot from the EEPROM, so you can possibly brick it if you change register 17 i believe the firmware understands that, and will refuse to program reg17 with the old config flags I see, but why its different? Could be that previous ...
by cleverca22
Thu Mar 19, 2020 10:09 pm
Forum: Troubleshooting
Topic: wrong OTP for pi4?
Replies: 6
Views: 222

Re: wrong OTP for pi4?

the only thing the OTP really does on a 4, is control its ability to boot from the EEPROM, so you can possibly brick it if you change register 17

i believe the firmware understands that, and will refuse to program reg17 with the old config flags
by cleverca22
Thu Mar 19, 2020 8:57 pm
Forum: Troubleshooting
Topic: wrong OTP for pi4?
Replies: 6
Views: 222

Re: wrong OTP for pi4?

do you have access to a serial adapter?
what does it show on the serial port while booting?
by cleverca22
Thu Mar 19, 2020 1:07 am
Forum: Advanced users
Topic: The bootloader spends more than 6 seconds.
Replies: 1
Views: 200

Re: The bootloader spends more than 6 seconds.

https://gist.github.com/cleverca22/58784f67690bfb97492f3f439ff00ed7 this is a program i wrote about a month ago to help track down boot time issues its currently configured to work on an RPI4 the rpi has a free-running timer, that begins counting the moment the cpu comes out of reset, and this code ...
by cleverca22
Tue Mar 17, 2020 10:16 pm
Forum: Bare metal, Assembly language
Topic: [SOLVED] custom recovery.bin files
Replies: 21
Views: 1968

Re: [SOLVED] custom recovery.bin files

i believe the main rule for `bootcode.bin` is that it be under 128kb (the L2 cache size) and that it be properly signed the large jump in size might be new features being added, possibly allowing the firmware to boot from other sources the differences in memsys, could be compression or patching, ide...
by cleverca22
Tue Mar 17, 2020 10:12 pm
Forum: Troubleshooting
Topic: Rpi 4 dead, trying to avoid repeat. (1st timer)
Replies: 10
Views: 786

Re: Rpi 4 dead, trying to avoid repeat. (1st timer)

random thought, if you plug the USB-C into another computer (linux would be simplest), does it appear as a USB device? I'll try that, not sure what it will do for me. if we are lucky, maybe the eeprom is just fried a bit, and the SoC might fall back into usb device boot (no, it cant boot from a usb...

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