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by dpotop
Wed Feb 07, 2018 1:18 pm
Forum: Other programming languages
Topic: Sonic Pi : balance between left and right to create a rotating impression
Replies: 2
Views: 1027

Sonic Pi : balance between left and right to create a rotating impression

Hello, I'd like to create the impression of sound source rotating around me. To do this, I need to control how the sound is transmitted to the left and right channels of my amplifier. I do not want to do this globally by controlling the output volume, because I want just one buffer to do this. How c...
by dpotop
Thu Jun 22, 2017 9:24 am
Forum: Beginners
Topic: Modify the binding of one single key under Raspbian
Replies: 0
Views: 234

Modify the binding of one single key under Raspbian

Hello, I'm trying to change the binding of one single key on my Raspberry Pi system. On my QWERTY keyboard I'm using an international mapping to write french. All letters are OK except one "ç" (C with cedilla). Some web pages suggested that it should be possible to write it using ALT-GR c. This did ...
by dpotop
Tue Jun 20, 2017 5:29 am
Forum: Troubleshooting
Topic: Persistent crashes on Pi3 (still!)
Replies: 10
Views: 1539

Re: Persistent crashes on Pi3 (still!)

Shea wrote:It is good to hear you found the problem. What is the made, and size of sd card that give you then problem ?
Kingston, 32G, microSDHC, class 10, made in Taiwan.
by dpotop
Mon Jun 19, 2017 9:10 pm
Forum: Troubleshooting
Topic: Persistent crashes on Pi3 (still!)
Replies: 10
Views: 1539

Re: Persistent crashes on Pi3 (still!)

Ok, I found the problem: SD card incompatibility. The card works all right, just not with the RPis...
by dpotop
Mon Jun 19, 2017 5:35 pm
Forum: Troubleshooting
Topic: Persistent crashes on Pi3 (still!)
Replies: 10
Views: 1539

Re: Persistent crashes on Pi3 (still!)

Increasing the swap does not work. From the default 100M I pushed it to 512M, and it blocks the same way. I'll try the Pi2 and keep you informed.
by dpotop
Mon Jun 19, 2017 8:16 am
Forum: Troubleshooting
Topic: Persistent crashes on Pi3 (still!)
Replies: 10
Views: 1539

Re: Persistent crashes on Pi3 (still!)

I'll do that. What's funny, is that I can now deterministically reproduce my crash (by calling apt-get to update perl). Is there someone here interested in the SD card image, to test/debug it ? For instance, people developing Raspbian ? What I will also try is running the update on a Raspberry Pi 2...
by dpotop
Sat Jun 17, 2017 8:54 pm
Forum: Troubleshooting
Topic: Persistent crashes on Pi3 (still!)
Replies: 10
Views: 1539

Persistent crashes on Pi3 (still!)

Hello everybody, This is a recurring topic, but I could find no solution to my problem on existing posts. At the same time I can't believe I'm the only one having these problems. Here is my setting : I have 2 RPi3 cards, bought at a 10-month interval of time (meaning that there are few chances they ...
by dpotop
Sun Sep 25, 2016 12:35 pm
Forum: Automation, sensing and robotics
Topic: Battery pack compatibility...
Replies: 3
Views: 838

Re: Battery pack compatibility...

.... So I have two questions: 1. Does a simple micro USB to USB C adapter allow me to both charge and take power out of the battery pack through the USB C socket? 2. Can I take power from the other slot (supporting QuickCharge3.0) for the RPi3 ? Alternate question : can you point me to packs that w...
by dpotop
Sat Sep 24, 2016 10:15 pm
Forum: Automation, sensing and robotics
Topic: Battery pack compatibility...
Replies: 3
Views: 838

Battery pack compatibility...

Hello, I'm coming back with my questions on how to power the RPi3 (and some motors). I was thinking of buying this [url=https://www.amazon.com/Tronsmart-10400mAh-Portable-Charger-Technology/dp/B01KNJQZ4W/ref=sr_1_1?ie=UTF8&qid=1474754704&sr=8-1&keywords=Tronsmart+Presto+10400mAh] USB battery pack [/...
by dpotop
Mon Sep 19, 2016 5:57 am
Forum: Automation, sensing and robotics
Topic: Can I power a RPi3 with 4 C-size rechargeables ?
Replies: 14
Views: 2789

Re: Can I power a RPi3 with 4 C-size rechargeables ?

Hello again, Yes, there are 2 motors: one for thrust in the rear and one for steering in the front. Don't imagine anything fancy. I just took one of my son's ToysRUs cars that no longer worked. So, the motors are nothing like brushless or powerful. Still, the car used to work on 6xAA and was pretty ...
by dpotop
Wed Sep 14, 2016 10:44 am
Forum: Automation, sensing and robotics
Topic: Can I power a RPi3 with 4 C-size rechargeables ?
Replies: 14
Views: 2789

Re: Can I power a RPi3 with 4 C-size rechargeables ?

Thanks a lot for you advice. I now narrowed it down to 2 options: - A 5V USB powerbank , which seems to have the advantage of simplicity for the electric part. - 6xAA NiMh 2500mAh Eneloops with a smart charger and a UBEC rated at 3 amps . This solution has the advantage of reusing the battery holder...
by dpotop
Mon Sep 12, 2016 7:59 am
Forum: Bare metal, Assembly language
Topic: Pi camera input in bare metal
Replies: 1
Views: 1111

Pi camera input in bare metal

Hello, I'd be interested in reading video (or sequences of images) from my Pi camera in bare metal. I understand this is a difficult topic, and that one solution would be for me to dig into the kernel sources. However, it would be very useful if someone could point me to the relevant sources, and ma...
by dpotop
Sat Sep 10, 2016 9:31 pm
Forum: General discussion
Topic: RPi 3 SoC at nearly 100 °C, reporting 80 °C
Replies: 238
Views: 99299

Re: RPi 3 SoC at nearly 100 °C, reporting 80 °C

Small contribution to this thread: I also noticed a discrepancy between actual and measured temperature, but only after installing a heat sink on the SoC. Here's how it worked: - At first, I used my RPi3 without a heat sink. During heavy loads (e.g. compilation) temperature went to 80C and then sta...
by dpotop
Sat Sep 10, 2016 8:02 pm
Forum: Automation, sensing and robotics
Topic: Can I power a RPi3 with 4 C-size rechargeables ?
Replies: 14
Views: 2789

Can I power a RPi3 with 4 C-size rechargeables ?

Hello,

In other terms, is 4.8V enough to make RPi3 run?
I'm thinking of C-size rechargeables, of 3000mAh.
Is this realistic ?
I'm trying to avoid both building a power regulator
circuit, and buying large (and expensive, and non-standard)
battery packs.

Best,
Dpotop
by dpotop
Sat Sep 10, 2016 7:31 pm
Forum: C/C++
Topic: C++ slower than Python for OpenCV !
Replies: 6
Views: 4678

Re: C++ slower than Python for OpenCV !

I'm surprised as well (I'm using Pi3, OpenCV 3, Pi Camera V2, GCC (11?)). You didn't mention the driver for the camera I have a PiCamera version 1.3. For the driver, I have no idea. I just took an SD card pre-loaded with Noobs, and then upgraded the system using apt-get upgrade. I had no issues doin...
by dpotop
Sat Sep 10, 2016 2:59 pm
Forum: C/C++
Topic: C++ slower than Python for OpenCV !
Replies: 6
Views: 4678

Re: C++ slower than Python for OpenCV !

No debug mode for compilation. I first thought it's the cause of the slowdown, so I removed the option. With no significant impact on performance. I only have one installation of OpenCV on my RPi, which I have done by hand, making sure that both python and the C code use it... But of course there mu...
by dpotop
Sat Sep 10, 2016 1:22 pm
Forum: General discussion
Topic: RPi 3 SoC at nearly 100 °C, reporting 80 °C
Replies: 238
Views: 99299

Re: RPi 3 SoC at nearly 100 °C, reporting 80 °C

Small contribution to this thread: I also noticed a discrepancy between actual and measured temperature, but only after installing a heat sink on the SoC. Here's how it worked: - At first, I used my RPi3 without a heat sink. During heavy loads (e.g. compilation) temperature went to 80C and then stab...
by dpotop
Sat Sep 10, 2016 1:00 pm
Forum: C/C++
Topic: C++ slower than Python for OpenCV !
Replies: 6
Views: 4678

C++ slower than Python for OpenCV !

Hello, I have a RPi3 running OpenCV3 under raspbian with input from the Pi Camera. While I started (for simplicity) with Python, at some point I wanted to switch to C++, to get better performance. To my surprise, the C++ version of the same program with (seemingly) the same options is far worse, and...
by dpotop
Sat Sep 10, 2016 12:46 pm
Forum: Python
Topic: OpenCV latency (not throughput)
Replies: 0
Views: 531

OpenCV latency (not throughput)

Hello all, I have a nice RPi3 running Python2.7/OpenCV3 with the Pi Camera. I want to do some real-time detection, and I have some issues understanding where image processing latency is coming from. Mind you, I am really happy with the throughput, this is not an issue. Here is the problem: I am toyi...
by dpotop
Mon Mar 07, 2016 1:52 pm
Forum: Bare metal, Assembly language
Topic: RPi3 ethernet and wifi
Replies: 1
Views: 926

RPi3 ethernet and wifi

Hello, The wikipedia page of Raspberry Pi states that the new RPi3 has both ethernet and wifi and does not mention them being accessible through the USB chip. Is this the case ? If yes, it's a major improvement, but where can I find the documentation for the programming of the Ethernet chip? Best, D...
by dpotop
Thu Nov 26, 2015 7:02 pm
Forum: Bare metal, Assembly language
Topic: Ethernet: SPI vs USB
Replies: 2
Views: 1589

Ethernet: SPI vs USB

Hello everybody, I have written an OS for the RPi and I'd really like adding Ethernet networking support (bare Ethernet, for now). As far as I understand, there are two possible solutions: - Use the on-board USB-based Ethernet ports. - Use an SPI-based external module based on the ENC28J60 chip. I t...
by dpotop
Tue Jun 23, 2015 1:37 pm
Forum: Bare metal, Assembly language
Topic: Dedicating one core to hard realtime tasks
Replies: 26
Views: 12293

Re: Dedicating one core to hard realtime tasks

Hello mntmst,
mntmst wrote:If you do manufacturing engineering...
I don't. :D
Of course, you're doing manufacturing with your RPi, then the situation changes. But I was assuming a hobby usage.

dpotop
by dpotop
Fri Jun 19, 2015 11:58 am
Forum: Bare metal, Assembly language
Topic: Dedicating one core to hard realtime tasks
Replies: 26
Views: 12293

Re: Dedicating one core to hard realtime tasks

You may be able to live with the potential latencies introduced by the Pi's architecture, you may not. As noted above, everything depends on the size of the real-time code. If the whole code fits into 16k and all data fits into 16k, too, then he can disable cache coherency and execution of the RT c...
by dpotop
Thu Jun 18, 2015 6:11 pm
Forum: Bare metal, Assembly language
Topic: Managing the L2 cache on the RPi2
Replies: 1
Views: 909

Managing the L2 cache on the RPi2

Hello, Can anybody point me to documentation and examples helping me use the L2 cache of the RPi2. I didn't find the needed information in the ARM description of the SCU in cortex a7. What I would need to do is: - enable and disable the L2 cache, while keeping the L1 caches enabled - partition the L...
by dpotop
Thu Jun 18, 2015 11:40 am
Forum: Bare metal, Assembly language
Topic: Dedicating one core to hard realtime tasks
Replies: 26
Views: 12293

Re: Dedicating one core to hard realtime tasks

Even if you dedicate a core to bare metal, you will have interferences from the other cores when accessing RAM and L2 cache. Ensuring true isolation between cores on the RPi is not very easy. So, you should always expect some variability in execution times.

dpotop

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