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by jwatte
Sun Feb 21, 2016 7:04 am
Forum: Official Foundation Display
Topic: backlight, brightness control on official disp or another?
Replies: 4
Views: 2632

Re: backlight, brightness control on official disp or anothe

This code should work fine: f = open("/sys/class/backlight/rpi_backlight/brightness", "wb") f.write("80\n") f.close() If it doesn't work, then one of two things are wrong: 1) You're using a v1.0 display instead of the v1.1 display -- I don't know if backlight adjust actually works on 1.0. 2) You're ...
by jwatte
Sun Feb 21, 2016 6:44 am
Forum: Official Foundation Display
Topic: disable screensaver
Replies: 10
Views: 7347

Re: disable screensaver

I applied this change and rebooted, but the display backlight still turns off after a few minutes. (I'm booting into a logged-in X session.) For what it's worth, when the display has gone to sleep, putting 0 or 1 into the bl_power control file does NOT turn it on. I have to physically touch it to ge...
by jwatte
Sun Jun 07, 2015 9:27 pm
Forum: HATs and other add-ons
Topic: Question about HAT specification
Replies: 3
Views: 1819

Question about HAT specification

The HAT specification states: It uses a GPIO connector that spaces the HAT between 10mm and 12mm from the Pi (i.e. uses spacers between 10mm and 12mm). However, the RPi has black nylon spacers at the bottom of the GPIO pins already. To make a 10mm spacing, I'd need more like a 7.5mm header. Which ha...
by jwatte
Tue Apr 07, 2015 3:27 am
Forum: Camera board
Topic: Question about RaspiCam native resolution
Replies: 4
Views: 1879

Re: Question about RaspiCam native resolution

Also: When you say those formats are the only ones for 30 fps, what does that actually mean? If I ask for, say, 736x414, or 640x360, will those count as formats that will run at 30 fps, or does it have to be EXACTLY those formats?
by jwatte
Tue Apr 07, 2015 3:25 am
Forum: Advanced users
Topic: OMX h264 encoder
Replies: 17
Views: 10184

Re: OMX h264 encoder

The bitrate it chooses to output is much less than the maximum bitrate. I leave it at the default, but then only give it the small images, so I assume it should do great. I'll play with the quantization.
by jwatte
Tue Apr 07, 2015 3:23 am
Forum: Camera board
Topic: Question about RaspiCam native resolution
Replies: 4
Views: 1879

Re: Question about RaspiCam native resolution

If you're using MMAL via a modified raspivid, then the things to remember is that format->es.video.width must be a multiple of 32, but format->es.video.crop.width can be any multiple of 2. Likewise format->es.video.height must be a multiple of 16, but format->es.video.crop.height can be any multipl...
by jwatte
Tue Apr 07, 2015 3:17 am
Forum: Compute Module
Topic: Where do you get SO-DIMM slots?
Replies: 2
Views: 1372

Re: Where do you get SO-DIMM slots?

In the US, I like DigiKey. Here's a search for the part, but I don't know if this includes the cheapest versions. http://www.digikey.com/product-search/en?pv149=107&pv1061=12&FV=fff40016%2Cfff804a8&k=200+sodimm&mnonly=0&newproducts=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25 (About $3 a...
by jwatte
Tue Apr 07, 2015 3:15 am
Forum: Advanced users
Topic: How to have git remember SSH password
Replies: 5
Views: 3697

Re: How to have git remember SSH password

It's not "git" that is asking, it's "ssh" that's asking. "ssh" will by default try to load a key that is in the file "identity" in the .ssh directory, and if that key is protected with a passphrase, it will ask for that phrase. If it can't find that key, it will attempt to do a password-interactive ...
by jwatte
Tue Apr 07, 2015 3:10 am
Forum: Bare metal, Assembly language
Topic: Task Scheduling with Interrupts
Replies: 5
Views: 2482

Re: Task Scheduling with Interrupts

I don't know the ARM interrupt handler semantics, but in most CPUs, you have to store the register state of the thread, in addition to the PC and stack pointer information, in the thread control block. This is also important when a non-interrupt causes a context switch, such as when blocking on a se...
by jwatte
Tue Apr 07, 2015 2:58 am
Forum: Advanced users
Topic: MMAL: How do I get rid of VCOS_INLINE_DECL warnings?
Replies: 1
Views: 374

Re: MMAL: How do I get rid of VCOS_INLINE_DECL warnings?

That was not an April Fools joke -- I really want to know!
by jwatte
Mon Apr 06, 2015 12:15 am
Forum: HATs and other add-ons
Topic: AVRPi: ATmega32U4 and ATmega328 addon boards ("arduino")
Replies: 9
Views: 6627

Re: AVRPi: ATmega32U4 and ATmega328 addon boards ("arduino")

Then why would I want an AVR board at all? The Pi already has SPI, I2C, USART, and GPIO. The reason to use AVR 8-bit is to re-use existing Arduino libraries and shields. Else you might as well go with a more capable chip like the M4 used on the Teensy 3.1. BTW, the $20 Teensy is a great 3.3V, 5V tol...
by jwatte
Mon Apr 06, 2015 12:06 am
Forum: Graphics, sound and multimedia
Topic: Pi-based CarPC using iPhone for control?
Replies: 8
Views: 2506

Re: Pi-based CarPC using iPhone for control?

I don't think the iPhone allows that (it had only one WiFi chip) but it you use it as a hotspot, perhaps you can already see the raspberry on that hotspot network?
by jwatte
Mon Apr 06, 2015 12:04 am
Forum: Beginners
Topic: Controlling 6 Solenoid Valves Using Raspberry Pi B?
Replies: 6
Views: 2446

Re: Controlling 6 Solenoid Valves Using Raspberry Pi B?

Oh - the description didn't make it clear that it was buffered, but the circuit diagram does. I take back my suggestion it wouldn't work.
by jwatte
Sun Apr 05, 2015 9:54 pm
Forum: Graphics, sound and multimedia
Topic: Pi-based CarPC using iPhone for control?
Replies: 8
Views: 2506

Re: Pi-based CarPC using iPhone for control?

You can make the Raspberry Pi be its own wireless access point with a $10 USB wifi adapter and running hostapd. I'm using this one: http://www.amazon.com/gp/product/B00H95C0A2/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1 Works a treat! I use Wifi-B to get more robustness to interference; throughput o...
by jwatte
Sun Apr 05, 2015 9:52 pm
Forum: Off topic discussion
Topic: How do processors work?
Replies: 50
Views: 5191

Re: How do processors work?

The first time I built a 4-bit microcontroller from TTL ICs and hand-rolled microcode, was when this lightbulb went off for me! Modern RISC systems code the necessary "select" bits into the instruction format and just pipeline execution, rather than make the microcode just drive one thing at a time....
by jwatte
Sun Apr 05, 2015 9:46 pm
Forum: General discussion
Topic: Clone to slightly smaller SD
Replies: 9
Views: 2473

Re: Clone to slightly smaller SD

The ability to read/write an extra sdcard on the pi is important!
There are USB microSD card readers for $6 or so.
Then you can transfer individual partitions using "dd," or you can use something like "cpio" to transfer files rather than blocks.
by jwatte
Sun Apr 05, 2015 9:44 pm
Forum: HATs and other add-ons
Topic: AVRPi: ATmega32U4 and ATmega328 addon boards ("arduino")
Replies: 9
Views: 6627

Re: AVRPi: ATmega32U4 and ATmega328 addon boards ("arduino")

That was my thought as well -- the Arduino form factor would be the #1 thing someone would be looking for in a case like this.

Also, why 8 MHz? There's 5V available on the RPi header, so running at 16 MHz (like the Arduino) is probably a better match to people's expectations.
by jwatte
Sun Apr 05, 2015 9:42 pm
Forum: Beginners
Topic: Powering from 12 volt
Replies: 6
Views: 14621

Re: Powering from 12 volt

A slightly less bulky option is a 5A voltage regulator, preferrably a switching one to avoid a massive heat sink. I've used both of these, they both work great: https://www.pololu.com/product/2850 http://www.digikey.com/product-detail/en/OKI-78SR-5%2F1.5-W36-C/811-2196-5-ND/2259781 Note that the sec...
by jwatte
Sun Apr 05, 2015 9:29 pm
Forum: Beginners
Topic: Controlling 6 Solenoid Valves Using Raspberry Pi B?
Replies: 6
Views: 2446

Re: Controlling 6 Solenoid Valves Using Raspberry Pi B?

No, you need a buffer between the RPi and that board, because each of the relays draws 20 mA and needs 5V control; RPi only gives you 3.3V, and doesn't like it at all if 8 pins are all drawing 20 mA... That buffering isn't particularly hard; you could do it with one BS170 transistor and one pull-dow...
by jwatte
Sun Apr 05, 2015 9:20 pm
Forum: Advanced users
Topic: Support for OMX Face Recog
Replies: 13
Views: 2412

Re: Support for OMX Face Recog

it appears that OpenCV is currently unaccellerated on the Pi Well, yes-and-no. I'm running image processing at 30 fps on a Raspberry Pi 2, using the Raspberry Pi camera. I wrote this code in C++. I could link in OpenCV to process the data, but I didn't have to. The Pi 2 has two important improvemen...
by jwatte
Sun Apr 05, 2015 9:13 pm
Forum: Advanced users
Topic: OMX h264 encoder
Replies: 17
Views: 10184

Re: OMX h264 encoder

FWIW, I'm also not seeing great quality from raspivid using the built-in H.264 encoder. (This is using the Raspberry Pi camera) I'm using all default settings, 512x288 resolution, and 30 fps, on a RPi 2. Default settings. I'm wondering what I can do to improve quality? Set I-frame interval to 1 or 2...
by jwatte
Sun Apr 05, 2015 9:10 pm
Forum: Advanced users
Topic: Distributing software
Replies: 6
Views: 1070

Re: Distributing software

How big is the set of devices? Do you have control of all of them? For something simple, you could set up a master repository (a directory with ssh shell access for some user) and set up a crontab that does rsync from that master on each of the devices at a frequency you decide. You could also use v...
by jwatte
Sun Apr 05, 2015 9:06 pm
Forum: Camera board
Topic: Question about RaspiCam native resolution
Replies: 4
Views: 1879

Question about RaspiCam native resolution

I recently ran an autonomous car at robogames using a Raspberry Pi 2 and the RaspiCam. Great fun! I hacked up the raspivid example to send the preview stream to my own buffer for image recognition, while still encoding the H.264 stream to disk for after-action review. (I have plenty of takes of hitt...
by jwatte
Wed Apr 01, 2015 6:48 pm
Forum: Advanced users
Topic: MMAL: How do I get rid of VCOS_INLINE_DECL warnings?
Replies: 1
Views: 374

MMAL: How do I get rid of VCOS_INLINE_DECL warnings?

I generally compile with -Wall -Werror Unfortunately, the VCOS_INLINE_DECL macro used for some mmal functions generates a warning, because I get the inline declaration but not the definition. This comes from, for example, vcos_platform_types.h. How am I supposed to #define/#include these headers to ...
by jwatte
Mon Mar 30, 2015 4:35 pm
Forum: Camera board
Topic: [SOLVED] mmal_port_send_buffer - ENOMEM?
Replies: 22
Views: 4240

Re: [SOLVED] mmal_port_send_buffer - ENOMEM?

Currently I'm trying to get preview connected to the video renderer, video port to resizer, resizer callback to my opencv stuff
Did you get that working? Any notes, samples, or suggestions?

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