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by jjackowski
Mon Sep 07, 2015 11:24 pm
Forum: Gentoo
Topic: Install Gentoo on rpi2 but /usr/src is empty
Replies: 7
Views: 9549

Re: Install Gentoo on rpi2 but /usr/src is empty

In case anyone else is still reading this thread, I keep seeing this and it has never been a problem. I put Gentoo on a Raspberry Pi maybe a couple years ago, and more recently on a 2B. I do build the kernel, but on another much faster computer. I do not move the kernel source over to the Raspberry ...
by jjackowski
Wed Sep 17, 2014 8:41 pm
Forum: C/C++
Topic: restrictions when porting code in C
Replies: 3
Views: 711

Re: restrictions when porting code in C

armv6 doesn't support 64-bit code, but you're writing C code, not binary code, so you're fine. gcc has a non-standard 128-bit integer, but only for 64-bit targets like AMD64, not armv6 or armv7. Some data types are a different size, and data alignment can be different. Both can cause data structures...
by jjackowski
Sat Aug 02, 2014 12:36 am
Forum: General discussion
Topic: Help compiling kernel: external/built-in modules?
Replies: 1
Views: 606

Re: Help compiling kernel: external/built-in modules?

You've just about got it figured out. If the code is built-in, it'll become part of the big kernel image. If it is a module, it'll be in a separate file. Some things are needed immediately by the kernel and cannot be in a module. Often you can get around that by placing modules into a special file, ...
by jjackowski
Tue Jul 15, 2014 6:30 pm
Forum: Arch
Topic: NTP Problem
Replies: 7
Views: 3382

Re: NTP Problem

I had similar issues with the NTP client that were caused by a stupidly slow DHCP server. The network wasn't configured for a while after the login prompt was up, and the system didn't wait for the network or the NTP client while booting, and did not run the NTP client after the DHCP client finally ...
by jjackowski
Wed Jun 11, 2014 6:48 pm
Forum: Automation, sensing and robotics
Topic: Occupancy sensing
Replies: 6
Views: 4634

Re: Occupancy sensing

I've been slowly working towards a similar goal. I was thinking PIR in combination with some MLX90614s for places where people may not move much. There are some pressure sensors that might be useful, and maybe embedding a temperature sensor in furniture could work. Also, the camera module with some ...
by jjackowski
Wed Jun 04, 2014 5:54 pm
Forum: Gentoo
Topic: Gentoo for the Raspberry Pi - Overview
Replies: 4
Views: 5042

Re: Gentoo for the Raspberry Pi - Overview

Here is another option for speeding updates: distcc. I have found a cross compiling distcc setup to not be all that time consuming, save for waiting on crossdev to build things. It avoids emulators by letting a Raspberry Pi control the build, but lets me use an AMD64 system to assist. I was original...
by jjackowski
Tue Nov 05, 2013 10:48 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Sample code for reading MLX90614 IR thermometer?
Replies: 5
Views: 2844

Re: Sample code for reading MLX90614 IR thermometer?

Thanks to the repeated start issue, you won't get any temperature data from a MLX90614 unless you either patch the kernel, use the kernel's GPIO based I2C master, or interface directly with the hardware. There is a C library ( http://www.airspayce.com/mikem/bcm2835/ ) for such direct hardware interf...
by jjackowski
Wed Sep 18, 2013 8:36 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: [RESOLVED]Python smbus.read_i2c_block_data
Replies: 5
Views: 8902

Re: Python smbus.read_i2c_block_data

As I understand it, the block read and writes usually cause the address to increment as they operate on each word. They aren't very useful otherwise. The datasheet for the component will probably explicitly state if it does this, and if it even supports the block operations.
by jjackowski
Fri Sep 13, 2013 7:05 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Read-only SPI
Replies: 3
Views: 1279

Re: Read-only SPI

You can transfer some number of bytes. I think the Linux kernel interface will accept a NULL pointer to indicate there is nothing to send. I'm not sure about the bcm2835 library. If you have to specify an output buffer, just make a buffer on the stack and don't bother to initialize it. The output pi...
by jjackowski
Fri Sep 13, 2013 6:56 pm
Forum: Automation, sensing and robotics
Topic: Raspberry PI and bus master
Replies: 6
Views: 1867

Re: Raspberry PI and bus master

I haven't tried a DS2483, but I'm sure you're right that it will be more reliable than using a GPIO line, especially for more devices and longer cables. If I'm not mistaken, the Linux kernel has support for the DS2483.
by jjackowski
Thu Aug 29, 2013 8:45 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Some I2C related questions (interrupts, switching)
Replies: 3
Views: 2645

Re: Some I2C related questions (interrupts, switching)

You may be able poll those MCP23017 at more than 200Hz if nothing else uses that I2C bus. I'm not sure how the Linux kernel driver for them handles reads and writes; the details may make using the userspace i2c-dev interface faster or slower. The calls to i2c-dev are synchronous, so you might want t...
by jjackowski
Wed Aug 28, 2013 8:39 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Is there a SPI/I2C library that works with 2+ different apps
Replies: 2
Views: 552

Re: Is there a SPI/I2C library that works with 2+ different

Anything that goes through the Linux kernel's interfaces for these instead of something that uses /dev/mem to manipulate the hardware directly should work fine. Personally, I don't find the kernel's user-space interface with the ioctl function difficult to work with, but I may just be weird.
by jjackowski
Wed Aug 14, 2013 10:51 pm
Forum: C/C++
Topic: Eclipse - Error 127 - No information on unknown command
Replies: 6
Views: 5287

Re: Eclipse - Error 127 - No information on unknown command

Actually, I wrote that the system cannot find a library that gcc needs to run. gcc isn't doing anything useful because it always fails with the same error 127, even if you can't see the error. If you run it in one of the ways I suggested, you might get a better error message. As for 32 vs 64 bit stu...
by jjackowski
Tue Aug 13, 2013 11:42 pm
Forum: C/C++
Topic: Eclipse - Error 127 - No information on unknown command
Replies: 6
Views: 5287

Re: Eclipse - Error 127 - No information on unknown command

That error is usually caused by the system not finding some library that a program, gcc in this case, needs. I'm sure its giving back error 127 when you request the version, too. It might be that a required path isn't in the path environment variable. Try running it some other way, like from the Win...
by jjackowski
Mon Aug 05, 2013 6:59 pm
Forum: Automation, sensing and robotics
Topic: Weather Station (Predict weather)
Replies: 2
Views: 1686

Re: Weather Station (Predict weather)

To predict the weather requires a lot of information about conditions over a large area around the spot for the prediction. If you can get this information, you've probably got a network connection over which you can get a prediction from someone else. I did look at the software for forecasting a fe...
by jjackowski
Sat Aug 03, 2013 11:22 pm
Forum: Automation, sensing and robotics
Topic: GPIO control between two RPis
Replies: 9
Views: 2919

Re: GPIO control between two RPis

I'd suggest using TCP sockets. UDP sends separate messages that might be lost, while TCP manages a continuous stream and will provide an error if data is not delivered. I haven't done this in Python, just C and C++, but it looks like Python has a similar interface. This seems to be an easy place to ...
by jjackowski
Sat Jul 13, 2013 4:34 pm
Forum: Linux Kernel
Topic: I2C repeated starts implemented in the kernel
Replies: 2
Views: 2580

I2C repeated starts implemented in the kernel

I really wanted to use user-space SMBus code for the MLX90614 sensor. Finding code to access the Raspberry Pi's I2C master directly was easy, but I couldn't find a fix for the kernel. So I fixed it. The changes are in bcm2708_i2c_master_xfer() of i2c-bcm2708.c. http://home.hiwaay.net/~jeffj1/i2c-bcm...
by jjackowski
Thu Jun 06, 2013 7:12 pm
Forum: C/C++
Topic: Developing code in linux PC and compiling source on pi?
Replies: 6
Views: 2206

Re: Developing code in linux PC and compiling source on pi?

You don't even have to copy the files. I've got my deskunder running an NFS server and mount that on the Raspberry Pi so that I can access the files from both computers while storing them only on the deskunder. Remote debugging with gdb works, but gdb is generally unpleasant to use directly. So far,...
by jjackowski
Mon May 13, 2013 7:17 pm
Forum: Automation, sensing and robotics
Topic: Hardware Advice Requested
Replies: 8
Views: 1407

Re: Hardware Advice Requested

One possibility might be to always be capturing frames and inspect a subset of two frames to determine if a sufficiently large enough change has occurred to be considered interesting. That could be used as a trigger for actually recording the captured video. There are people playing around with Open...
by jjackowski
Wed May 01, 2013 4:52 pm
Forum: C/C++
Topic: swp{b} is deprecated
Replies: 1
Views: 1191

Re: swp{b} is deprecated

I get the same warning when invoking gcc with fairly simple parameters that are in no way specific to any target. I wondered about it for a while, but then decided to ignore it.
by jjackowski
Tue Apr 30, 2013 5:31 pm
Forum: Automation, sensing and robotics
Topic: Source code to w1-therm?
Replies: 41
Views: 32239

Re: Source code to w1-therm?

Is it possible to make this GPIO pin change and rebuild the required modules without recompiling the whole kernel? Yes, as long as the w1 stuff is in modules as apposed to built-into the kernel. In that case, you can even unload the old modules and then load the new ones without rebooting. Make the...
by jjackowski
Tue Apr 30, 2013 2:16 pm
Forum: C/C++
Topic: Getting keybord input, GLES, no X
Replies: 3
Views: 851

Re: Getting keybord input, GLES, no X

Seems like SDL has some way of doing it. That code should at least have some hints since it can be built to work without X.
by jjackowski
Tue Apr 30, 2013 1:30 pm
Forum: Gentoo
Topic: Building Firefox 20
Replies: 5
Views: 5822

Re: Building Firefox 20

Xeonist, I missed the libjpeg issues somehow. Maybe my build died before it got there. I tried again with the system-jpeg use flag in hopes of avoiding that problem and maybe picking up some recent fixes. The build still fails, but libjpeg doesn't kill it, so I don't know if the flag solves anything...
by jjackowski
Tue Apr 23, 2013 2:24 pm
Forum: Automation, sensing and robotics
Topic: Raspberry Pi vs. Beagle Bone Black
Replies: 3
Views: 1198

Re: Raspberry Pi vs. Beagle Bone Black

I'm curious as to the new Beagle Bone's interrupt latency. I measured the Raspberry Pi's response to GPIO interrupts at between 9 to 11 microseconds, which isn't terribly good.
by jjackowski
Sat Apr 13, 2013 11:36 pm
Forum: Automation, sensing and robotics
Topic: Source code to w1-therm?
Replies: 41
Views: 32239

Re: Source code to w1-therm?

Glad I could help! I'm not sure why it is hard coded like that. The module even has a parameter; it tells the module what pin to use for a strong pull-up. Seems like a fine example for making it take an optional parameter for the one-wire pin, and falling back on the hard coded one as a default. Cer...

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