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by knute
Tue Jun 16, 2015 2:58 am
Forum: Troubleshooting
Topic: Can't get I2C to work?
Replies: 1
Views: 435

Can't get I2C to work?

New copy of raspian from the 2015-05-05 file. Answered the raspi-config questions to install and load I2C. Added i2c-dev to /etc/modules. /etc/modprobe.d/raspi-blacklist.conf is empty. Device tree is enabled and /boot/config.txt has dtparam=i2c_arm=on line. Pi has been rebooted. PiGlow is plugged in...
by knute
Tue Jun 16, 2015 2:10 am
Forum: Networking and servers
Topic: Connect two Pi's over Ethernet in Client/Server config
Replies: 1
Views: 714

Re: Connect two Pi's over Ethernet in Client/Server config

Give them static IP addresses on the same network and connect a cable between them.
by knute
Tue Jun 02, 2015 3:55 am
Forum: Beginners
Topic: SSH Key Authentication Not Working
Replies: 1
Views: 318

Re: SSH Key Authentication Not Working

You probably know this but the authorized_keys and the id_rsa files need to be user rw only.
by knute
Tue Jun 02, 2015 3:23 am
Forum: Raspberry Pi OS
Topic: Configuring Network using dhcpcd
Replies: 11
Views: 73552

Re: Configuring Network using dhcpcd

It's still not clear to me what "manual" means in the /etc/network/interfaces file. When I installed the raspberrypi-net-mods it overwrote my /etc/network/interfaces file that had my static IP setup in it. When I reboot it it still comes up with the old static IP address even though all of that is n...
by knute
Thu May 28, 2015 5:14 pm
Forum: Troubleshooting
Topic: Latest raspi and no wifi?
Replies: 2
Views: 423

Re: Latest raspi and no wifi?

I could have sworn that I rebooted but I must not have. When I started it up this morning it's working fine now.

Thanks
by knute
Wed May 27, 2015 2:43 am
Forum: Troubleshooting
Topic: Latest raspi and no wifi?
Replies: 2
Views: 423

Latest raspi and no wifi?

I got a new SD card, loaded the May 5th raspi on it and started it up. Works fine except WIFI. There's a new applet for the WIFI that finds my access points and takes the key but gives me an address that isn't on my network. The address I get is 169.254.93.83. It should be 192.168.3.? wpa_gui isn't ...
by knute
Sat May 23, 2015 10:04 pm
Forum: Beginners
Topic: Install JAVA??
Replies: 3
Views: 565

Re: Install JAVA??

1. Download the latest JDK from the Oracle website

2. Unzip and untar it to someplace, /opt maybe

3. You can run alternatives from the command line but it is really easier to install the GUI version, galternatives, and use that to point to all of the Java tools

4. You are done!
by knute
Fri May 22, 2015 3:02 am
Forum: Python
Topic: Displaying shapes on gif file
Replies: 3
Views: 667

Re: Displaying shapes on gif file

How do you combine a cirlce with a gif image? Simple Java program draws a circle on a GIF (or a JPG or BMP) and saves it in a new file. import java.awt.*; import java.awt.event.*; import java.awt.image.*; import java.io.*; import javax.imageio.*; import javax.swing.*; /** * Compile: javac DrawCircl...
by knute
Sat Apr 18, 2015 4:51 pm
Forum: C/C++
Topic: C pigpio DHTXX sensors
Replies: 8
Views: 1540

Re: C pigpio DHTXX sensors

The DHT readings on user space is restricted by the cpu usage. Did you try to overclock your PI. Daniel Good suggestion. When I overclock the Pi I get the same results. Without the code raising the line to high, I get a lot of errors caused by missing transition(s). With the code in it works every ...
by knute
Fri Apr 17, 2015 8:01 pm
Forum: C/C++
Topic: C pigpio DHTXX sensors
Replies: 8
Views: 1540

Re: C pigpio DHTXX sensors

Adding a pullup resistor doesn't appear to make it work any differently. It still has about 10% errors without the call in the code to raise the line high. Any ideas?

thanks,
by knute
Thu Apr 16, 2015 7:47 pm
Forum: C/C++
Topic: C pigpio DHTXX sensors
Replies: 8
Views: 1540

Re: C pigpio DHTXX sensors

It might be interesting to experiment with a slightly different trigger method. Rather than // return bus to high for 20us gpioWrite(gpio,1); gpioDelay(20); // change to input mode gpioSetMode(gpio,PI_INPUT); as the line is pulled high with a resistor you could lose the first three lines and just h...
by knute
Wed Apr 15, 2015 11:49 pm
Forum: C/C++
Topic: C pigpio DHTXX sensors
Replies: 8
Views: 1540

C pigpio DHTXX sensors

I haven't programmed C in a couple of decades but I'm probably more familiar with it than Python. So when I went looking for some example C code to read the DHTXX sensors I couldn't find much. The one piece of code that I found used wiringPi worked but it got a lot of failed reads and so I was looki...
by knute
Wed Apr 15, 2015 11:11 pm
Forum: Java
Topic: UDP receive buffer size?
Replies: 9
Views: 6101

Re: UDP receive buffer size?

Thanks, I'll try that.
by knute
Sat Apr 11, 2015 3:40 am
Forum: Java
Topic: UDP receive buffer size?
Replies: 9
Views: 6101

Re: UDP receive buffer size?

Having a larger buffer is a simple solution to prevent buffer overrun and loss of data. Surely you must already cope with missing (and duplicated or reordered) data, since you are using UDP, which does not guarantee delivery in the first place. Yes, I send it again shortly. [quot="jojopi"]It is ano...
by knute
Sat Apr 11, 2015 3:36 am
Forum: Java
Topic: UDP receive buffer size?
Replies: 9
Views: 6101

Re: UDP receive buffer size?

DougieLawson wrote:
knute wrote: So does anybody actually know how to make the UDP buffer larger?
Five seconds spent googling turns up
sysctl -w net.core.rmem_max=2097152
Thanks for that. Now I know why it didn't work when I tried it before. It doesn't persist after a reboot. Is there a way to make it stay?
by knute
Fri Apr 03, 2015 4:10 am
Forum: Java
Topic: UDP receive buffer size?
Replies: 9
Views: 6101

Re: UDP receive buffer size?

Our server ultimately has to serve data to as many as 2000 sites. More full up socket connections than we want to have on a PC. There are periodic record bursts that are 1MB. The holdup in the Pi appears to be reading the data from the buffer into my program. Having a larger buffer is a simple solut...
by knute
Wed Apr 01, 2015 3:49 am
Forum: Java
Topic: UDP receive buffer size?
Replies: 9
Views: 6101

UDP receive buffer size?

I'm testing a Java program on my A+ and I would like to set the socket receive buffer size to 2MB but using Socket.setReceiveBufferSize(1024*2048) gives me a buffer size of 163840. The default is 81920. Is there another way to increase the buffer size with an OS option somewhere?

Thanks,

knute...
by knute
Mon Mar 09, 2015 3:19 am
Forum: Java
Topic: Could not initialize class gnu.io.CommPortIdentifier on tomc
Replies: 7
Views: 4237

Re: Could not initialize class gnu.io.CommPortIdentifier on

The -cp option is ignored if -jar is specified. -jar filename Executes a program encapsulated in a JAR file. The filename argument is the name of a JAR file with a manifest that contains a line in the form Main-Class:classname that defines the class with the public static void main(String[] args) me...
by knute
Fri Mar 06, 2015 5:27 am
Forum: Beginners
Topic: Send an email when raspberry pi is connected to the internet
Replies: 11
Views: 2825

Re: Send an email when raspberry pi is connected to the inte

Write a program...

What is controlling whether or not the Pi is connected to the internet? Is the connection dodgy?
by knute
Sat Feb 21, 2015 4:52 am
Forum: Troubleshooting
Topic: Pi2 boot problem?
Replies: 2
Views: 555

Pi2 boot problem?

My new Pi2 occaisionally fails to boot. It produces a lot of error messages but a couple are repeated: WARNING: CPU: 2 PID: 55 at drivers/mmc/host/bcm2835-mmc.c:476 mmcblk0: unknown error -5 sending read/write command, card status 0x900 The green light that usually flashes during boot comes on solid...
by knute
Fri Feb 20, 2015 3:56 am
Forum: Raspberry Pi OS
Topic: Pi2 error dialog when starting X?
Replies: 3
Views: 921

Re: Pi2 error dialog when starting X?

OK
by knute
Thu Feb 19, 2015 5:31 am
Forum: Raspberry Pi OS
Topic: Pi2 error dialog when starting X?
Replies: 3
Views: 921

Pi2 error dialog when starting X?

So I just got my Pi2, loaded up an SD card with the lastest Raspbian image (2015-02-16) and booted it up. Had a few problems that I think are SD card related so I programmed another one and it appears to be more stable. When I start X for the first time after a boot, I get a dialog with the followin...
by knute
Sun Dec 21, 2014 5:49 pm
Forum: Raspberry Pi OS
Topic: fullscreen analog clock?
Replies: 8
Views: 8437

Re: fullscreen analog clock?

Oh goody! I get to learn to work in yet another programming language! lol :lol: Seriously, though, I have a feeling that this is probably going to be what I am looking for. Off I go to read a couple of books real quick ;) Thank you! It may take a little while for me to be able to take a look it thi...
by knute
Sun Dec 21, 2014 1:28 am
Forum: Raspberry Pi OS
Topic: fullscreen analog clock?
Replies: 8
Views: 8437

Re: fullscreen analog clock?

How about a Java analog clock? import java.awt.*; import java.awt.event.*; import java.awt.geom.*; import java.util.*; import javax.swing.*; /** * AnalogClock is a resizable Swing component that draws an analog clock. * * @author Knute Johnson */ public class AnalogClock extends JComponent implement...
by knute
Fri Dec 19, 2014 4:23 am
Forum: General discussion
Topic: Good Wireless Keyboard????
Replies: 8
Views: 2301

Re: Good Wireless Keyboard????

I bought a Gear Head 2.4Ghz wireless touch keyboard at Fry's the other day. It has a USB dongle that communicates with the keyboard/touchpad. It works well enough, with the occasional hiccup. The keyboard is really too small for my fat fingers, I have to use one finger at a time. I bought it to use ...

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