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by findx
Mon Feb 29, 2016 7:23 pm
Forum: General discussion
Topic: The Raspberry Pi 3 Model B Q&A thread
Replies: 457
Views: 210522

Re: The Raspberry Pi 3 Model B Q&A thread

Does the new WiFi and Bluetooth capability use the GPIO bank 0 IRQ line? Or is it only using alternate pin IRQ functionality? I'm curious because it affects multiplexing of multiple devices on the GPIO bank 0 IRQ.
by findx
Mon Feb 29, 2016 5:36 pm
Forum: General discussion
Topic: The Raspberry Pi 3 Model B Q&A thread
Replies: 457
Views: 210522

Re: The Raspberry Pi 3 Model B Q&A thread

Does the RPi 3 still use the same Synopsys USB IP core as previous versions? Gert van Loo said last year that they "could not touch the USB" on the RPi 2, and I'm curious if that's changed on the RPi 3.
by findx
Thu Jan 21, 2016 6:08 am
Forum: Advanced users
Topic: HOWTO: Enable USB device mode on Pi Zero
Replies: 68
Views: 46818

Re: HOWTO: Enable USB device mode on Pi Zero

@mattmiller Thanks for running a test!
by findx
Tue Jan 19, 2016 7:45 pm
Forum: Advanced users
Topic: HOWTO: Enable USB device mode on Pi Zero
Replies: 68
Views: 46818

Re: HOWTO: Enable USB device mode on Pi Zero

Has anyone done a speed benchmark for the virtual Ethernet adapter? I'm curious how much data it can push, but I unfortunately do not have an RPi Zero to test it.
by findx
Sat Dec 05, 2015 10:20 pm
Forum: Bare metal, Assembly language
Topic: How to enumerate interrupts?
Replies: 1
Views: 804

Re: How to enumerate interrupts?

This is a bare metal forum, not a Linux forum. It would be best if you directed your questions to the Linux forum. That said, to help point you in the right direction, please look at the datasheet , section 6. There are only 54 GPIO pins — the same 54 you found with your code. These pins are grouped...
by findx
Thu Nov 26, 2015 9:17 am
Forum: Bare metal, Assembly language
Topic: disable_pvt
Replies: 5
Views: 1965

Re: disable_pvt

In the end it was disable_pvt not working. The newest firmware includes the fix:

https://github.com/raspberrypi/firmware ... 4ee471f446
by findx
Wed Nov 18, 2015 7:39 pm
Forum: Bare metal, Assembly language
Topic: disable_pvt
Replies: 5
Views: 1965

Re: disable_pvt

Sorry to bring this thread back from the dead, but I think I've identified the firmware commit that causes the problem. I posted a description on GitHub: https://github.com/raspberrypi/firmware/issues/497
by findx
Thu Apr 16, 2015 4:40 am
Forum: Bare metal, Assembly language
Topic: disable_pvt
Replies: 5
Views: 1965

Re: disable_pvt

I'm seeing something with more recent firmware, too. I observed random execution delays in my GPIO FIQ code on the RPi 1 B when I watched in infinite persistence on my scope. This was causing data glitches visible in my web UI (the symptom I was originally investigating). Since I'm using my own 3.12...
by findx
Tue Mar 17, 2015 7:41 pm
Forum: General discussion
Topic: The Raspberry Pi 2 Q&A thread
Replies: 442
Views: 113500

Re: The Raspberry Pi 2 Q&A thread

The USB timer/counter was actually something that I requested - there's some Gert magic in there that means you can route the ARMCTRL FIQ to an arbitrary core and multiplex it with a very basic timer (19.2MHz/24-bit compare-counter) to get around some of the limitations in the OTG core. Will specif...
by findx
Wed Feb 18, 2015 7:26 pm
Forum: General discussion
Topic: The Raspberry Pi 2 Q&A thread
Replies: 442
Views: 113500

Re: The Raspberry Pi 2 Q&A thread

The USB timer/counter was actually something that I requested - there's some Gert magic in there that means you can route the ARMCTRL FIQ to an arbitrary core and multiplex it with a very basic timer (19.2MHz/24-bit compare-counter) to get around some of the limitations in the OTG core. Will specif...
by findx
Tue Feb 03, 2015 7:27 am
Forum: General discussion
Topic: Raspberry Pi 2
Replies: 161
Views: 24106

Re: Raspberry Pi 2

What happened to there definitely wont be another Pi for a couple of years :?: Not really happy if im honest, I know it's only a cheap device, but lying so blatantly to the userbase is ****. Parts like the Odroid C1 (also $35) probably forced them to launch sooner than expected: http://www.hardkern...
by findx
Tue Feb 03, 2015 5:24 am
Forum: General discussion
Topic: Raspberry Pi 2
Replies: 161
Views: 24106

Re: Raspberry Pi 2

I wonder if they've fixed the USB controller in this silicon so it doesn't need all that FIQ fun. We could not touch the USB but the ARM has a special 'USB timer' I added as response to a request from the USB dive driver developer... Cool, it's good to know something may improve with that. I pull r...
by findx
Mon Feb 02, 2015 10:00 am
Forum: General discussion
Topic: Raspberry Pi 2
Replies: 161
Views: 24106

Re: Raspberry Pi 2

I wonder if they've fixed the USB controller in this silicon so it doesn't need all that FIQ fun.
by findx
Fri Jan 09, 2015 5:43 pm
Forum: Automation, sensing and robotics
Topic: Controlling Gasoline Engine Combustion
Replies: 2
Views: 743

Controlling Gasoline Engine Combustion

Here's a short (2 min) video of PREEMPT_RT Linux controlling a gasoline engine from one burn to the next using the Raspberry Pi: https://www.youtube.com/watch?v=qQG7ocnE3EA It's using an adaptive machine learning algorithm that can predict near chaotic combustion in real-time. A paper about the algo...
by findx
Wed Nov 05, 2014 6:10 am
Forum: Raspbian
Topic: FIQ latency
Replies: 5
Views: 2772

Re: FIQ latency

I don't have hard numbers because it's sufficiently fast for my application, but it takes <= 1 microsecond for the FIQ to respond to a GPIO event under Linux. I unfortunately don't have time at the moment to write a full reply with code corrections / a minimal working example, but I would caution yo...
by findx
Mon Sep 29, 2014 3:43 pm
Forum: Bare metal, Assembly language
Topic: Raspberry Pi Machine Learning for Near Chaotic Combustion
Replies: 3
Views: 2340

Re: Raspberry Pi Machine Learning for Near Chaotic Combustio

Diesel engines have issues with soot particles and NOx (a toxic smog and acid rain precursor). There are solutions to deal with those issues, but they are not ideal (e.g. requiring you to buy Diesel Exhaust Fluid (DEF) to clean up NOx with additional catalyst hardware at a rate of ~2% DEF per quanti...
by findx
Sun Sep 28, 2014 9:34 pm
Forum: Bare metal, Assembly language
Topic: Raspberry Pi Machine Learning for Near Chaotic Combustion
Replies: 3
Views: 2340

Raspberry Pi Machine Learning for Near Chaotic Combustion

I posted here earlier about the FIQ size under Linux, and I thought I'd post a follow up about where things stand now that all my FIQ and real-time Linux issues are resolved. The link below is a video of the Raspberry Pi connected a gasoline engine running an adaptive machine learning algorithm that...
by findx
Wed Feb 19, 2014 9:58 pm
Forum: Bare metal, Assembly language
Topic: FIQ Size
Replies: 24
Views: 5678

Re: FIQ Size

Cool! That's good to know.
by findx
Tue Feb 11, 2014 6:22 am
Forum: Bare metal, Assembly language
Topic: Defining addresses and bit-fields with structs
Replies: 12
Views: 3250

Re: Defining addresses and bit-fields with structs

There are also instances where bitfields are unable to set individual bits. For example, you have to feed password bits at the same time you set other the bits on the RPi GPIO pads control register: http://www.scribd.com/doc/101830961/GPIO-Pads-Control2 So you're back to or'ing together bits for a s...
by findx
Tue Feb 11, 2014 5:20 am
Forum: Bare metal, Assembly language
Topic: FIQ Size
Replies: 24
Views: 5678

Re: FIQ Size

I absolutely agree with both you and Abrash... you have to measure these things, and assume nothing. Here's a quote from Abrash's Black Book, Chapter 3: A case in point: A few years back, I came across an article about 8088 assembly language called “Optimizing for Speed.” Now, “optimize” is not a wo...
by findx
Sat Feb 08, 2014 11:44 pm
Forum: Bare metal, Assembly language
Topic: FIQ Size
Replies: 24
Views: 5678

Re: FIQ Size

Well, I was able to get my code to fit by cheating a little. The low hanging fruit was to optimize this 3 instruction wait macro, which I used 5 different places to space out the correct parallel bus bit timing: // Previous wait code... 3 instructions and no need to mess with R14 .macro WAIT loops, ...
by findx
Sat Feb 08, 2014 4:47 am
Forum: Bare metal, Assembly language
Topic: FIQ Size
Replies: 24
Views: 5678

Re: FIQ Size

Based on the kernel code described in my previous post, it's crashing because I'm overwriting the "vector stubs." I don't think I need to do any more work to diagnose the issue since it's pretty clear to me where the 0x200 magic number comes from now. In my original post I had mistakenly thought the...
by findx
Sat Feb 08, 2014 3:23 am
Forum: Bare metal, Assembly language
Topic: FIQ Size
Replies: 24
Views: 5678

Re: FIQ Size

Well I've answered my own question with some experimenting and poking around to find the right section of kernel code to read. Experiment : Having an FIQ code size larger than 0x200-0x1C = 0x1E4 kills my system. Kernel code : The kernel apparently installs the vector table at the high location of 0x...
by findx
Fri Feb 07, 2014 8:45 pm
Forum: Bare metal, Assembly language
Topic: FIQ Size
Replies: 24
Views: 5678

Re: FIQ Size

@chrisryall My code is time critical, but can likely tolerate an additional branch. In terms of documenting the system, however, I think it would be good know whether a branch is even needed in this case. I'm also just barely over the historically quoted size for FIQ code. I wish I had a straightfor...
by findx
Fri Feb 07, 2014 6:35 pm
Forum: Bare metal, Assembly language
Topic: FIQ Size
Replies: 24
Views: 5678

Re: FIQ Size

For an IRQ or other exception you normally branch wherever you want subject to the relative branch size constraint, however the FIQ is specifically designed to be at the end of the table so you can either branch or install a small bit of code without branching elsewhere. The latter is what I have be...

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