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by Lomax
Tue Sep 10, 2019 1:02 pm
Forum: General discussion
Topic: Still confused, what is better for my SD card?
Replies: 19
Views: 924

Re: Still confused, what is better for my SD card?

You don't want to do more writes than necessary! Just leave the controller alone doing wear leveling for you. There is a rule of thumb to leave at least 10% of the capacity free to avoid slowdowns and early failure. If you need more space it's time for an upgrade. Thanks, I'll go with 6Gb partition...
by Lomax
Tue Sep 10, 2019 10:26 am
Forum: General discussion
Topic: Still confused, what is better for my SD card?
Replies: 19
Views: 924

Re: Still confused, what is better for my SD card?

well it depends on the controller on the card it may or may not work... the only way you can help is not by writing it so it's nearly full all the time I usually use these cards when I need high reliability: Sandisk Industrial MicroSD.jpg Not terribly expensive, IIRC ~£10 each when bought in quanti...
by Lomax
Tue Sep 10, 2019 9:49 am
Forum: General discussion
Topic: Still confused, what is better for my SD card?
Replies: 19
Views: 924

Re: Still confused, what is better for my SD card?

just because you have defined partitions for yourself, which are just ranges of block numbers, does not mean the SD card won't use whatever actual physical space it likes. I've read this sentence several times but still not sure if that's a "yes, leaving unpartitioned space helps with wear levellin...
by Lomax
Tue Sep 10, 2019 8:57 am
Forum: General discussion
Topic: Still confused, what is better for my SD card?
Replies: 19
Views: 924

Re: Still confused, what is better for my SD card?

Re. wear levelling, if I only need a fraction of the space on a given card, is it better to leave some space unpartitioned, or should my partitions take up 100% of what's available? Maybe it makes no difference?
by Lomax
Mon May 06, 2019 11:23 am
Forum: Graphics, sound and multimedia
Topic: Oculus Rift CV1 compatibility
Replies: 7
Views: 594

Re: Oculus Rift CV1 compatibility

I'll have to give up on using a Pi for this. I'm guessing an Odroid C2 would be able to provide the required bandwidth? It does HDMI 2.0 4K@60 Hz. We're only going to use the Rift for stereoscopic 360° video playback, so 3D performance is pretty irrelevant. Edit: I've now ordered an MSI "Cubi N" min...
by Lomax
Sun May 05, 2019 9:26 pm
Forum: Graphics, sound and multimedia
Topic: Oculus Rift CV1 compatibility
Replies: 7
Views: 594

Re: Oculus Rift CV1 compatibility

Another update: Just to verify the basic approach to getting the Rift to work at all on Linux (i.e. using OpenHMD) I did a quick test with a Devuan live USB stick on a spare laptop. Sure enough, after downloading and building OpenHMD (and dependencies), the "simple" example they provide fired up the...
by Lomax
Sun May 05, 2019 7:42 pm
Forum: Graphics, sound and multimedia
Topic: Oculus Rift CV1 compatibility
Replies: 7
Views: 594

Re: Oculus Rift CV1 compatibility

Some further developments. I figured I'd try with some common display mode that the Rift might support and set /boot/config.txt to hdmi_drive=2 hdmi_force_hotplug=1 hdmi_group=1 hdmi_mode=16 which should mean 1080p@60Hz. But while I do get a response from the Rift with this setting (the LED turns wh...
by Lomax
Sun May 05, 2019 3:28 pm
Forum: Graphics, sound and multimedia
Topic: Oculus Rift CV1 compatibility
Replies: 7
Views: 594

Re: Oculus Rift CV1 compatibility

I am such an idiot sometimes... The weird SyncMaster EDID data likely appeared because I've explicitly told the Pi to ignore actual EDID data by having hdmi_ignore_edid=0xa5000080 in /boot/config.txt :lol: I commented out all my HDMI related settings in the config and rebooted - but now tvservice do...
by Lomax
Sat May 04, 2019 11:10 am
Forum: Graphics, sound and multimedia
Topic: Oculus Rift CV1 compatibility
Replies: 7
Views: 594

Re: Oculus Rift CV1 compatibility

Many thanks 6by9, I hadn't tried the tvservice command. Alas the output seems wildly incorrect: $ tvservice -d edid.dat Written 256 bytes to edid.dat $ parse-edid < edid.dat Checksum Correct Section "Monitor" Identifier "SyncMaster" ModelName "SyncMaster" VendorName "SAM" # Monitor Manufactured week...
by Lomax
Fri May 03, 2019 2:50 pm
Forum: Graphics, sound and multimedia
Topic: Oculus Rift CV1 compatibility
Replies: 7
Views: 594

Re: Oculus Rift CV1 compatibility

I finally found some timing data on the Oculus Rift CV1: Pixel Clock: 296.75MHz Horizontal Active: 2160 Horizontal Blanking: 80 Vertical Active: 1200 Vertical Blanking: 272 Horizontal Sync Offset: 8 Horizontal Sync Pulse: 32 Vertical Sync Offset: 50 Vertical Sync Pulse: 2 Horizontal Display Size: 11...
by Lomax
Wed May 01, 2019 11:42 pm
Forum: Graphics, sound and multimedia
Topic: Oculus Rift CV1 compatibility
Replies: 7
Views: 594

Oculus Rift CV1 compatibility

Somewhat naively I thought it would be pretty much a "plug'n'play" operation to at least get a picture displaying on an Oculus Rift CV1 VR headset. Hours later and I haven't managed to get a single pixel to light up. Haven't been able to find much info on the Internet either; I found some blog posts...
by Lomax
Sat Mar 23, 2019 6:56 pm
Forum: Graphics, sound and multimedia
Topic: Suggestions for multiple amplified audio outputs
Replies: 3
Views: 357

Re: Suggestions for multiple amplified audio outputs

Did you test it since audio_pwm_mode=2 was introduced? analog + something stereo turned into dual mono would sum to 3. Ah yes, good point - I'd forgotten the internal audio had seen some quality improvement. Not sure if it can drive the loudspeakers directly (I think they're 8Ω, something like 2" p...
by Lomax
Sat Mar 23, 2019 3:28 pm
Forum: Graphics, sound and multimedia
Topic: Suggestions for multiple amplified audio outputs
Replies: 3
Views: 357

Suggestions for multiple amplified audio outputs

I'm currently working on-site with an interactive exhibition, which makes extensive use of the Pi. Annoyingly, one exhibit includes three separate (mono) "earphones" where visitors can listen to different sounds. I would normally use something like the JustBoom Amp Zero for anything requiring <=2 ch...
by Lomax
Sun Mar 17, 2019 3:40 pm
Forum: General discussion
Topic: Houseboat home automation / surveillance system
Replies: 53
Views: 8695

Re: Houseboat home automation / surveillance system

I thought I would give this topic a little bump. It's of real interest to me and it would be great to see what progress you've made in the last 2 years! Thanks Ollie, I've been meaning to post an update for ages but never seem to get around to it! I lived aboard for seven months in 2018, but have s...
by Lomax
Sun Feb 24, 2019 1:50 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Curious SPI behaviour with spidev-3.4
Replies: 5
Views: 966

Re: Curious SPI behaviour with spidev-3.4

I soon found @razi's post mentioning that the clock frequency needed to be explicitly set for the max7219 Python SPI library to work correctly on Pi3 systems . FTFY. It's all SPI in python or any programming language with the 4.14 kernel or later Ah, good, thank you! Looking at your first chart of ...
by Lomax
Sun Feb 24, 2019 12:23 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Curious SPI behaviour with spidev-3.4
Replies: 5
Views: 966

Re: Curious SPI behaviour with spidev-3.4

Sometimes it helps to be stubborn - I just wish I knew beforehand when that is. This time it paid off: just after I posted the above, I (somewhat desperately) searched the forums for "max7219", in the hope that a recommendation for some other library might turn up (though a similar search on Github ...
by Lomax
Sat Feb 23, 2019 11:49 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Curious SPI behaviour with spidev-3.4
Replies: 5
Views: 966

Re: Curious SPI behaviour with spidev-3.4

Ok, so I buckled under and replaced the max7219 Python library with the latest version - now called Luma.LED_Matrix and of course it all works perfectly. My preferred version 0.2.3 is quite old, from 2016, but it is nice and clean unlike the whole "Luma" thing which is a big sprawling library that s...
by Lomax
Fri Feb 22, 2019 12:54 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Curious SPI behaviour with spidev-3.4
Replies: 5
Views: 966

Curious SPI behaviour with spidev-3.4

I'm trying to get a Pi Zero W to talk to a MAX7219 LED driver over SPI using spidev-3.4 and the Python max7219 library v0.2.3 , but the LED driver doesn't respond and the data coming out of the SPI0 port when running the included example looks very odd: https://i.imgur.com/NBcD6Qe.png While I'm some...
by Lomax
Mon Feb 04, 2019 5:11 pm
Forum: Troubleshooting
Topic: RPi.GPIO: RuntimeError: No access to /dev/mem. Try running as root!
Replies: 5
Views: 546

Re: RPi.GPIO: RuntimeError: No access to /dev/mem. Try running as root!

I didn't understand what you do to solve the problem. Could you please give more details? I solved the problem by upgrading the RPi.GPIO Python library to v0.6.5 (from v0.6.4, which has this bug ). Raspbian ships v0.6.4 so I upgraded via pip. I solved this problem by adding the user you are using t...
by Lomax
Wed Jan 16, 2019 8:29 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Can an LCD share the SPI bus with another device
Replies: 3
Views: 472

Re: Can an LCD share the SPI bus with another device

There's two SPI buses and five chip select (chip enable) pins on the 40 pin header. You can have five SPI devices. Yep, SPI0 with two chip select and SPI1 with three. But I need the SPI1 pins for other use (I2S audio) so only have SPI0 and CE0/CE1. I'm worried that toggling between the LCD and anot...
by Lomax
Tue Jan 15, 2019 9:55 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Can an LCD share the SPI bus with another device
Replies: 3
Views: 472

Can an LCD share the SPI bus with another device

Sketching on a portable device based on the Pi Zero W, for which I'd like to use a Sharp "Memory LCD" display. These have a SPI interface, and should work with the FBTFT framebuffer. But I have another device I'd like to include, which also uses SPI, and only SPI0 will be free. Can the LCD share the...
by Lomax
Thu Jan 10, 2019 10:48 am
Forum: Troubleshooting
Topic: RPi.GPIO: RuntimeError: No access to /dev/mem. Try running as root!
Replies: 5
Views: 546

Re: RPi.GPIO: RuntimeError: No access to /dev/mem. Try running as root!

Ok, I finally found the problem: a bug was introduced in the RPi.GPIO library v0.6.4, and subsequently fixed in 0.6.5, see https://github.com/RPi-Distro/python-gp ... issues/687 Removing the version shipped by Raspbian and installing via pip pulled in 0.6.5 and the issue went away.
by Lomax
Tue Jan 08, 2019 2:16 pm
Forum: Troubleshooting
Topic: RPi.GPIO: RuntimeError: No access to /dev/mem. Try running as root!
Replies: 5
Views: 546

Re: RPi.GPIO: RuntimeError: No access to /dev/mem. Try running as root!

Try: sudo -i then run it. Thanks, already tried that. Found the problem though: I'm using the Adafruit RGB matrix "bonnet", and it seems to hog all the pins if configured first - swapping the init blocks around (GPIO first) seems to have solved it. Confusing error message, but I suppose it makes se...
by Lomax
Tue Jan 08, 2019 1:55 pm
Forum: Troubleshooting
Topic: RPi.GPIO: RuntimeError: No access to /dev/mem. Try running as root!
Replies: 5
Views: 546

RPi.GPIO: RuntimeError: No access to /dev/mem. Try running as root!

On site working, stressed out because I want to demo before end of play - stumped by this absurdity: sudo python matrix_v2.py Traceback (most recent call last): File "matrix_v2.py", line 126, in <module> GPIO.setup(button, GPIO.IN, pull_up_down=GPIO.PUD_UP) RuntimeError: No access to /dev/mem. Try r...
by Lomax
Sun Aug 19, 2018 11:43 am
Forum: Automation, sensing and robotics
Topic: RFID aperture detection
Replies: 1
Views: 425

RFID aperture detection

Hi all, I'm hoping to come up with a method to detect the passage of an object through one or other aperture using RFID. Would it be possible to make an RFID antenna "loop" around an opening such that tags passing through are read, while any passing on the outside are not? I've looked briefly at (ex...

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