Ubuntu 9.04 + Virtual Box (non ose) + usb grayed out
No commentsto solve this
add yourself to the virtual box group
type “grep vboxusers /etc/group” to get your id .. it will be the number
add
none /proc/bus/usb usbfs devgid=###,devmode=664 0 0
to your /etc/fstab where ### is the number you got with the previous command.
i tried all the other stuff, spent all day on it this worked .. if you have version 9.04 of ubuntu do this ! If you have VirtualBox ose from the package manager your usb devices wont work at all. Just go to the virtual box webpage and get the deb.
Ubuntu + VirtualBox + Existing WinXP 64 Hopefully !:
No commentsThis will hopefully tell you how to install virtual box in ubuntu, and have it use your existing windows partition. Of course, no one wants to reinstall all their stuff in the “virtual drive”. This is my first time using a virtual machine. This is based off the tutorials at http://ubuntuforums.org/showthread.php?t=769883 but that didnt work for me so this is what i did to make it work on my machine. A lot of it is the same.
Create a grub boot cd
First you might want to create a boot cd as a easy way to boot your partitions. This first line just takes your current config and moves it to your home directory so you can edit it then turn it into a iso.
cd ; mkdir -p iso/boot/grub ; cp /usr/lib/grub/*-pc/stage2_eltorito /boot/grub/menu.lst iso/boot/grub <strong>Edit the menu.lst in our soon to come boot cd</strong>
at this point we want to edit this file so we can make it ONLY boot our windows partition. If you boot the partition your on in a virtual machine its horrible i’ve heard so we dont want it to default to our ubuntu partition or something.
gedit ~/iso/boot/grub/menu.lst
Now go to the part where it has all the ubutnu or other os’s options and delete all that, most of the entries look like this. Only leave the last one which is your windows partition.
title Ubuntu 8.10, kernel 2.6.27-11-generic uuid 6bb9b9cc-0bc9-4b1f-af2e-bb675a993b65 kernel /boot/vmlinuz-2.6.27-11-generic root=UUID=6bb9b9cc-0bc9-4b1f-af2e-bb675a993b65 ro xforcevesa quiet splash vga=791 initrd /boot/initrd.img-2.6.27-11-generic quiet
Then on your windows partition modify it to look similar to this, the main thing i did was changed “root” to “rootnoverify”
# This entry automatically added by the Debian installer for a non-linux OS # on /dev/sda1 title Windows XP Professional x64 Edition rootnoverify (hd0,0) # savedefault !! comment this out makeactive chainloader +1
Make the boot CD iso
Now save and close that gedit window. Then make the grub stuff we were just messing with into a bootable iso.
cd ; mkisofs -R -b boot/grub/stage2_eltorito -no-emul-boot -boot-load-size 4 -boot-info-table -o grub.iso iso <strong>Make sure you have latest version of VirtualBox</strong>
At this point i totally removed my old version of virtual box using package manager, then i installed the new version from virtualbox.org using their easy package installer thing. You need the version 2.1+ to get support for 64bit os’s. I installed version 2.2 … so this tutorial is working for that version.
After i installed i didnt see it anywhere so i went to a terminal and typed “VirtualBox” to start it … yes the case matters.
Add your user to disk and vboxusers
In order for you to run the command we need to run next your user must be part of a group that is allowed to do this so we type this.
sudo usermod -a -G disk sudo usermod -a -G vboxusers <strong>Setup our passthrough virtual drive</strong>
then run this command to make our weird passthrough thing that links to our real physical partition.
VBoxManage internalcommands createrawvmdk -filename ~/.VirtualBox/WinHD.vmdk -rawdisk /dev/sda -partitions 1 -relative -register
Please note the “/dev/sda -partitions 1″ specifies partition one of my first sata disk… change this to your windows partition.
Create different profile for windows MUST DO !!
Ok now you must also at this point boot into windows and create another “profile” to boot into when you boot from linux. If not your hardware profile will get messed up when you boot into it from linux and you will not be able to use windows by itself anymore. So go into windows, right click my computer -> properties -> Hardware -> hardware profiles ->copy. Then name your second one to something you want, and make sure the timer is like 30 seconds so you can choose.
Create and run new virtual machine
Ok now boot back into linux, open a terminal type “VirtualBox” create a new virtual machine as type windows, use the drive we made and tell it to also mount a iso, use the iso we made.
The first time i tried it it said “error 15 file not found” … which i had been getting a lot of, dont fret just type “c” to get a command then type
grub: rootnoverify (hd0,0) grub: makeactive grub: chainloader +1 grub: boot
I cant because i dont have hardware virtualization in my cpu but you might
Then windows tries to start but cant because it still thinks its running on a 32 bit machine … lets go look in the virtual box settings for our virtual machine.
Ok, this story does not have a happy ending. Turns out my processor E4400 does not support VT or whatever it is. Its called hardware virtualiziation, and you need it to run a 64 bit guest OS. So even if i was in windows 7 using this feature to run Win XP 64 it would not work. Sorry everyone. You should note that everything else worked its just that windows 64 bit was unable to start due to the above problem.
Here is a list of cpu’s and if they have hardware virtualization
Testing RCT-433-AS-TRANSMITTER and RCR-433-RECIVER
No commentsBrief Description
My purpose was to test this transmitter/receiver pair to see how far i could go and still reliably transmit data. I used my protoboard to transmit. The reciever was attached to a uart to rs232 converter then to the db9 port on my computer and i watched the input from hyperterminal.
Equipment
- ProtoBoard
- rct-433-as transmitter Mouser Part # 509-RCT-433-AS
- rcr-433 reciever Mouser Part #509-RCR-433-RPR
- A transistor and some 10K resistors for Conversion
- A few 4.7uF and .01uF Filter Capacitors
Prelab
Get and study data sheets for the transmitter and reciever. Brush up on rs-232 and ttl signaling levels.
Procedure
The first thing i did was get the Conversion circuit working. I’ve found that the other circuit i have listed does not work well with the 2N3904/6 transistors that i have on hand. I was only able to get the uart to rs232 portion to work, as soon as i plugged in the capacitor or the line going to rs-232 RX the circuit would stop working. So I only hooked up half of the ciruit using a 2N3906 and three 10K resistors. You can do that or use the other one way circuit. You should be comfortable enough with the signalling levels by this point to do this easily, if not i suggest you go back to those sections.
After thats hooked up connect it to the tx pin on the pic to make sure its transmitting correctly. Then hook up the reciever and put the data out line where your pic was connected (before the 10K going into the base of the transistor). You can get the data sheets for the reciever and transmitter in the links that i posted above in the equipment bullets. Hooking up the reciever is really simple, its just ground and power lines and a data out. I hook up all the ground and power lines just to be sure, and when in doubt remember vsS = “sink” so its the ground.
I hooked the transmitter into my “protoboard”.
There is a program on the pic that just transmits a number like 10 times and then does a newline. That way i can print out lots of data and see what number it messed up on. I used the lowest setting i could for the pic, since it has a 20Mhz clock i can use any baud rate slower than 1200.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 | #include <16F877.h> #device adc=8 #use delay(clock=20000000) #fuses NOWDT,HS,NOPUT,NOLVP #use rs232(baud=1200,parity=E,xmit=PIN_C6,rcv=PIN_C7,bits=8) int i =0; int j=0; void main() { setup_adc_ports(NO_ANALOGS); setup_adc(ADC_OFF); setup_psp(PSP_DISABLED); setup_spi(FALSE); setup_timer_0(RTCC_INTERNAL|RTCC_DIV_1); setup_timer_1(T1_DISABLED); setup_timer_2(T2_DISABLED,0,1); output_b(0xFF); printf("\f \f \f \r \f \f \f \r \f \f \f \r"); printf("Start"); while(1){ for (j=0;j<10;j++){ printf(".%i",i); } printf("\r\n"); i++; } } |
Filter Capacitors
In the datasheet for both the transmitter and reciver it says you should use a “bypass” and “filter” cap. I noticed a great improvement of signal quality when i installed these. Pretty much for both of them i just connected them between ground and power in close proximity to the chip, I did this on both the tx and rx ends. You should be able to make it out from the pictures.
Antenna
There is some weird calculation to get “1/4″ of the wave or soemthing like that to calculate the optimum lenght of the antenna. Other people calculated it to 17cm. POST LINK HERE So, I just used a 17cm peice of telephone wire.
Conclusions
The pair works pretty good going at 1200 baud, I was able to transmit through walls. I transmitted at least 20 feet away through walls without loosing any info. This was only after installing the filter capacitors though.
In the datasheets it recommends that you invert the output signal on both ends. This allows you to only transmit when you are actually transmitting, if you dont do this to hold the line without sending data you have to send a ‘1′, but if you invert before it hits the transmitter and then invert coming out of the reciever then you wont need to waste power. If you are transmitting from the pic then you need to set the INVERT option in your program, or you can just invert after that. I didnt implement this part but i might later on.
When you are not transmitting the reciever picks up some weird square wave that does strange things. Then, when you start to transmit some of this weird square wave is picked up in the beggining of your signal, this almost always makes the first part of a string of data get garbled. You can get around this by just constantly transmitting data, which might not be efficent. Possibly you could create some kind of circuit to filter this out, or maybe by inverting the singal it would help ? Just something to consider.
Depending on the needed applications of this it seems to be a very nice way to transmit data, I plan on making a RC car, for that it should work just fine.
My Linux Firewall Script
9 comments so farThis is a continuation of articles “using iptables on your linux router“ and “how to setup your slackware linux box as a router“. This is the script that im pretty much finished with and how it works.
Hardware Setup
This is a basic diagram of my network setup. Crossover cables are denoted with ‘C’. This does not represent the actual spacing between items at all, for instance PC 2 is about 100ft away from the hub, the hub is right on top of the server.
Eth1 Network (192.168.10.0)
Very Un-trusted !
Only allow ports 80, and 22
PC1 can be allowed samba ports also
Eth2 Network(192.168.1.0)
Very trusted
All Packets are passed directly through
Firewall Script Flow Chart
This is a flow chart that explains how the firewall handles packets.
After making all this i realized that everything goes differently, packets go to see if its pc3 then to see if eth1 then they go to the firewall table to see if established/related, that is of course if they made it that far. If they were eth1 then they would have gone to net two. So please realize this above diagram is not exactly like my script, but very similar.
For simplicity I don’t include the “firewall” table which just accepts all local loopback and then goes to the trusted table. Really I should eliminate the “firewall” table, feel free to. The “NETTWO” table is dedicated to the unsecure network, It only allows port 80, 22 and PC1. PC1 is also pretty restricted. The table “NETTWO” hooks into the wifi router, which I am VERY weary of, I do further security on that router, its just a old Linksys wireless router. Its actually the router that I replaced my linux box with.
Anyway without further a due here is the actual script.
#!/bin/bash RETVAL=0 external_int="eth0" external_ip="`ifconfig $external_int | grep 'inet addr' | awk '{print $2}' | sed -e 's/.*://'`" # start the firewall start() { # set all default behaviour to accept iptables -P INPUT ACCEPT iptables -P OUTPUT ACCEPT iptables -P FORWARD ACCEPT # create new chains for firewall and trusted filtering iptables -N FIREWALL iptables -N TRUSTED iptables -N NETTWO # temp? tables for subnetwork of wifi, luis and garage computer # Log chain iptables -N LOG_DROP iptables -A LOG_DROP -j LOG --log-prefix '[IPTABLES DROP] : ' iptables -A LOG_DROP -j DROP # allow established and related incoming connetions only iptables -A FIREWALL -i eth0 -m state --state ESTABLISHED,RELATED -j ACCEPT # Allow self communication iptables -A FIREWALL -i lo -j ACCEPT iptables -A FIREWALL -o lo -j ACCEPT # send all package to the trusted chain iptables -A FIREWALL -j TRUSTED # drop all other packets iptables -A FIREWALL -j LOG_DROP ############################ # Prerouting, to speed up things ############################ # give the ubuntu pc a green light to do whatever, compleatly trusted ! (to firewall only) # ubuntu pc is connected to eth2 and has static ip of 192.168.1.11 iptables -A INPUT -j ACCEPT -p all -s 192.168.1.11 -i eth2 iptables -A OUTPUT -j ACCEPT -p all -d 192.168.1.11 -o eth2 # for the subnetwork that has luis and wifi we send it to its own table iptables -A INPUT -i eth1 -j NETTWO # send all input packets to the firewall chain iptables -A INPUT -j FIREWALL ############################ # Begin Forward Table and Inet sharing ############################ # forward all traffic coming from eth1 to eth 0 ( make all eth1's stuff go to the net) iptables -A FORWARD -i eth1 -o eth0 -j ACCEPT # forward only established or related connections from eth0 to eth1 ( so only stuff a local lanputer has started) iptables -A FORWARD -i eth0 -o eth1 -m state --state ESTABLISHED,RELATED -j ACCEPT # same as above but for eth2 (gigabit connection) iptables -A FORWARD -i eth2 -o eth0 -j ACCEPT iptables -A FORWARD -i eth0 -o eth2 -m state --state ESTABLISHED,RELATED -j ACCEPT # forward all sof2mp test stuff to this computer (take all connections to server) iptables -A FORWARD -i eth0 -o eth2 -p udp -m udp --dport 20100:20112 -j ACCEPT # broadcast the sof2 mp test server iptables -A FORWARD -i eth0 -o eth2 -p tcp -m tcp --dport 20100:20112 -j ACCEPT # any packets that get to this point are logged then dropped iptables -A FORWARD -j LOG_DROP # masquerade the ip's so they look like they are "all from one" machine iptables -A POSTROUTING -t nat -o eth0 -j MASQUERADE # turn forwarding on "tell the kernel" echo 1 > /proc/sys/net/ipv4/ip_forward ############################ # network two routing table, for subnetwork with luis and wifi # only port 80 and 22 are allowed, the rest are logged/dropped ############################ iptables -A NETTWO -p tcp -m tcp --dport 80 -j ACCEPT iptables -A NETTWO -p tcp -m tcp --dport 22 -j ACCEPT #iptables -A NETTWO -m mac --mac-source "pc2's mac" -p tcp -m tcp --dport 137:139 -j ACCEPT #iptables -A NETTWO -m mac --mac-source "pc2's mac" -j ACCEPT iptables -A NETTWO -j LOG --log-prefix '[NETTWO DROP] : ' iptables -A NETTWO -j DROP ############################ # Begin Trusted Table ############################ # Allow http, the eth+ defines "all" ethernet devices iptables -A TRUSTED -i eth+ -p tcp -m tcp --dport 80 -j ACCEPT # Allow http, the eth+ defines "all" ethernet devices iptables -A TRUSTED -i eth1 -p tcp -m tcp --dport 80 -j ACCEPT # Allow https iptables -A TRUSTED -o eth0 -p udp -m udp --dport 443 -j ACCEPT iptables -A TRUSTED -o eth0 -p tcp -m tcp --dport 443 -j ACCEPT # Allow SSH iptables -A TRUSTED -i eth+ -p tcp -m tcp --dport 22 -j ACCEPT # sof II test iptables -A TRUSTED -i eth0 -p tcp -m tcp --dport 20100 -j ACCEPT iptables -A TRUSTED -i eth0 -p udp -m udp --dport 20100 -j ACCEPT # Nexuiz iptables -A TRUSTED -i eth0 -p tcp -m tcp --dport 26000 -j ACCEPT iptables -A TRUSTED -i eth0 -p udp -m udp --dport 26000 -j ACCEPT # teamspeak iptables -A TRUSTED -i eth0 -p tcp -m tcp --dport 8767 -j ACCEPT iptables -A TRUSTED -i eth0 -p udp -m udp --dport 8767 -j ACCEPT # allow samba server for print and files to local nics only iptables -A TRUSTED -i eth1 -p tcp -m tcp --dport 137:139 -j ACCEPT iptables -A TRUSTED -i eth2 -p tcp -m tcp --dport 137:139 -j ACCEPT iptables -A TRUSTED -i eth1 -p tcp -m tcp --dport 445 -j ACCEPT iptables -A TRUSTED -i eth2 -p tcp -m tcp --dport 445 -j ACCEPT # log and drop all packets going through the trusted chain that make it this far iptables -A TRUSTED -j LOG_DROP # end message echo "- Iptables Script ran, security enabled" RETVAL=0 } # open everything and forward everything dumb() { # set all default behaviour to accept iptables -P INPUT ACCEPT iptables -P OUTPUT ACCEPT iptables -P FORWARD ACCEPT # now forward everything # forward all traffic coming from eth2to eth 0 (all ubuntu's computer goes to net) iptables -A FORWARD -i eth1 -o eth2 -j ACCEPT # forward all traffic from eth0 to eth2, all traffic from net to ubuntu computer iptables -A FORWARD -i eth2 -o eth1 -j ACCEPT # same as above but for eth1 (local lan slow) iptables -A FORWARD -i eth2 -o eth0 -j ACCEPT iptables -A FORWARD -i eth0 -o eth2 -j ACCEPT iptables -t nat -A PREROUTING -p udp -i eth0 -d $external_ip --dport 20100:20112 -j DNAT --to-destination 192.168.1.11 iptables -t nat -A PREROUTING -p tcp -i eth0 -d $external_ip --dport 20100:20112 -j DNAT --to-destination 192.168.1.11 # masquerade the ip's so they look like they are "all from one" machine iptables -A POSTROUTING -t nat -o eth0 -j MASQUERADE # turn forwarding on "tell the kernel" echo 1 > /proc/sys/net/ipv4/ip_forward echo "+ everything accepted, everything forwarded"; } # stop the firewall (everything is open !) stop() { # set the default policy iptables -P INPUT ACCEPT # accept all incoming packets iptables -P FORWARD ACCEPT # forward all packets to other puters (flood) iptables -P OUTPUT ACCEPT # accept all outgoing packets and send them # set default policy for the NAT table iptables -t nat -P PREROUTING ACCEPT iptables -t nat -P POSTROUTING ACCEPT iptables -t nat -P OUTPUT ACCEPT # delete all old rules iptables -F # flush iptables -t nat -F # flust nat table # delete all chains iptables -X iptables -t nat -X echo "+ All tables flushed" RETVAL=0 } lockdown() { echo "locking down everything" iptables -t nat -P PREROUTING DROP iptables -t nat -P POSTROUTING DROP iptables -t nat -P OUTPUT DROP iptables -t nat -P PREROUTING DROP iptables -t nat -P POSTROUTING DROP iptables -t nat -P OUTPUT DROP echo "itz locked down" } # case statement to call the correct function, exept status which is in the case case $1 in start) start ;; dumb) stop dumb ;; stop) stop ;; restart) stop start ;; status) iptables -L iptables -t nat -L RETVAL=0 ;; lockdown) stop lockdown ;; *) echo "Usage: Firewall (start|stop|restart|status)" esac exit
Thats pretty much it. I’m still kinda dumb when it comes to the forwarding part, so be careful of that part. Also when i allow pc2 to connect to samba ports i use its mac addres so replace “pc2 mac” with the mac address without quotes. Like this 00:00:00:00:00
Im dropping packets like there is no tommorrow. I’ve found that pc1 has something on it that is always sending packets to weird ports/ip’s they are all getting blocked.
Please comment if you know how i can improve this, or can point out any errors.
Another note, if you have email coming out from your server be sure to enable port 25, or whatever port you use. I just did that to mine.
Standard Lab Journal Format that I will be using
No commentsI’ve been wanting to organize my findings in a easy to read/reference way. So, I’ll be using a standard lab journal format for most of the things that i start as of now. Of course, it does not apply to everything. I’ve done so much stuff that i never wrote down anywhere, i want to be sure i can look back at stuff i do from now on. Anyway the standard format ill be using (thanks to my teachers)
Standard Lab Format
The following is a description of the standard lab format to be used:
I. Each lab entry should start with the title of the experiment and a brief description
II. The equipment to be used should be listed; leave some room below the initial list to add additional equipment and parts.
III.A prelab section (when applicable) should include any preliminary work to be done prior to coming to the lab.
IV. The procedure section describes the activities done in the lab. The reader of your journal should be able to follow your description without referring to a manual or handout, but you may summarize in your own words. Record your data, figures, sketches and observations. Be sure to label everything.
V. In the conclusions, you should write in a narrative style. Summarize your results and condense data when appropriate. Answer all questions asked.
RS232 Revisited
No commentsAbstract
Even though I have studied this subject several times it still continues to annoy me. This will be a in depth disscussion (kinda for myself) of the signal levels and such. Im wondering if CCS C is inverting the signal coming out of the pic so that its ready for consumption by the db9.
This straight out sort of conversion works off of the fact that most rs232 with short range cables can work just fine with +/- 3 volts. So if you use a transistor to invert the pic signal and a resistor to sink the current when the line is 0 you will get +/-3 volts to drive the rs232 line. So basically we invert the data coming out of the pic and add a resistor to that so when the pic outputs a 1 it is inverted to a 0 then sunk to the resistor to make -3 ish. This is best looked at with a table
Table 1
Pic out | RS-232 In
0volt | +3volt
5volt | -3volt
This is because for the pic a ‘1′ is 5v and for the rs-232 a ‘1′ is less than -3volts, likewize for the pic a ‘0′ is 0v and for rs-232 it is above 3v. So its pretty easy (in theory) to convert from the pic to rs-232, converting from rs-232 to pic levels is more tricky though. But, enough theory and such lets see what we actually get through the scope.
Results
Here I will show you (and myself) the results i get from rs232 and pic while sending the same characters. Hopefully after looking at everything and putting it in perspective we will be able to clearly see whats going on, or we will realize what we are doing wrong.
Setting the scope (soundcard scope)
I’m going to send ‘A’ then ‘a’ at 1200 baud via the pic, and via rs-232, we will be using eight bits with one stop bit. This makes 9 bits total so 1200/9 gives ~133 Hz for each bit. A less confusing way of figuring this out is: we have 1200 bits per second so thats 1/1200 8.3e-4 seconds or (*1000) .83 milliseconds for each bit. We know that we are getting 9 bits so to see the “whole thing” we use .83ms*9bits= 7.5ms. When i set my scope to 8ms i see nothing so i will just use about 60ms then zoom in.
Getting the shot
If you turn on your speakers and your using the soundcard scope you will be able to “hear” the bits go through. I use this as a metronome and i hit the run/stop button to get a good shot of what was sent. Then in the mid bottom i go to the “measure” setting and put it on cursor time. Then i get the blue lines and drag them from the start till about 130hz. This is what i get
So where i have the blue lines is the first char ‘A’ and the rest is the second char ‘a’. From http://www.asciitable.com/ we know that ‘A’ is 65D or 1000001 in binary. Looking at the output we can see we have something like 10???01, we know those four bits so the rest must be 9-4=5. But, I think there is always a “start” bit so that would make it 10 bits we really have so 10-4=6, and that chunk in the middle is all 1’s so 1011111101 is what we have which looks like
start bit | (data)’ | stop bit
I know we cant tell with this one but the data is sent lsb first, and yes that is the inverse of the data. So, where there was a 1 there is a 0 and so forth. This is what we get out of the pic, there is no manipulation its just “putc(’A')” so either it should be inverted, or ccs c is inverting it for us. Looking at the ‘a’ we see it is 1100001, and we are getting 10???001. Since we can make out 5 bits, 5 are left that chunk is 1’s so we get 1011111001. Which is just like before start/stop bits and lsb first inverted data. You dont have to figure out just by looking at it what the bits are you can start from the first bit and set f=134/9 and see what each bit is if need be.
Doing the same thing with RS232
It wasnt as easy to get the shot with rs232 but i opened hyperterminal set bits to 8 stop bits to one and baud to 1200. Then while hitting ‘A’ i hurried up and hit run/stop to get this.
From before we know that ‘A’ is 1000001, and yes all that below the red line is negative so we get “1011111101″, assuming that second bit is supposed to be above 3v (what else?). Also i already inverted everything from rs232 to ttl in my head. So we see that here too we get the data portion inverted.
Well, this is what we are getting, but according to sites like http://www.winpicprog.co.uk/pic_tutorial7.htm we should be getting something compleatly different, mainly inverted stuff. But im going to see terminator “salvation” in a hour so ill have to come back to this 
Protoboard Version 0.2
1 comment so far
This is my second attempt at making a general purpose board for my pic 877’s. This time the plan was dont connect anything. So the only connectors on the board are iscp, power, and a 40 pin header.
My idea behind the 40 pin header was to be able to connect this board through a normal ide cable to other stuff. I had planned a nice clean structure for the pins, but after soldering things went wrong. Its very confusing when everything is backwards and upside down. None the less its mostly consistent.
So far its working well. The only problem i have had is shorting the +- and blowing up a pic, also the ide cables for more than one drive dont seem to work with it. I dont think ide cables that go to more than one drive are “straight through”.
For anyone curious about version 0.1 you can see a picture here, its in a box ill pull it out and do something useful with it one day, its pretty stable. Its just too big.
this is the bottom view of version 0.1
I’ll write more about this as i use it, im kinda in a hurry now. I want to do a little more and write a little less, but i also want to document everything i do. Even if I’m brief.
SoundCard Oscilloscope
No comments
This is a tool any engineer needs ! We cant all go out and buy a $1000 scope, but we can use some old pc to look at just about anything.
The soundcards in todays pc’s are able to read signal data and display it on your scree. Big suprise right ? This works just like your visualization for winamp or windows media player, a sound/signal goes through and something displays peaks and pits on the screen.
There is software that does this very well, the one i use is made in lab view. It works very well and i have become accustomed to it, but I did not pick it for any good reason other than it was the first one to come up in my google search. It was created with labview, but it is a normal program like any other. You can find it here http://www.zeitnitz.de/Christian/index.php?sel=scope_en
Dont Fry your soundcard !
One consideration that must be made is how do you hook stuff into your microphone without burning it up. You CANNOT just hook 5v into your soundcard and expect it to work. The max you can send to your soundcard is about 1v. What I did was use a voltage divider, R1=100K R2=10K. Using the equation for a voltage divider i get Vout = R2/(R1+R2)*Vin => 10/110*Vin which is about 1/11*Vin. So for 5volt logic level i get .45 and for 12v i get 1.09 which is about as high as i want to go. To tell you the truth i only use this for ttl voltage levels and sometimes rs-232, i would never plug this directly into a power supply or something.
There you go, for about 4 resistors and a 1/16 cable you have a soundcard Scope.
The only disadvantage is that you cant see the voltage of the incoming signal, but since we have a right and left signal you can connect the left signal to a +5v and use that for comparison. Also on the bottom where it says measure it allows you to measure the exact fq of bits and such. There isnt much that i cant do with this scope that i can do with the scopes at school. Also this is free and you can use your mouse and take screen shots easily.
In the top screen shot im recording the input and output of a rf system (backspace). And in this screenshot below im doing the same thing, the red lines are the reciever and the green lines are the transmitter. Im sending a “tab” which in ascii is 9 decimal or 1001 binary. If you look at the green one you can see the input is 101101111 which is nine bits. There is startbit | data` | stopbit. The data is inverted, not sure if it should be but thats the way i saw it come out of the pic too. Anyway the main reason is to show that i can clearly see the two signals and compare them to each other to make sure im getting what i should.
Blow UP your Pic’s
No commentsEver wonder what happens if you run too much current through a pic ?
Ever wonder what happens if you connect the power supply backwards?
Ever wonder what happens when you accidentally short pos/neg?
You get to see the inside of the chip ! Thats if your eyes where out of the way of the piece of glass like silicone that goes blasting out of the pic.
Needless to say
- the chip does not work anymore
- this could cut you or hit you in the eye
- be careful, wear glasses
- when you start thinking “just a little more power” STOP
RS-232 to serial Conversion, using 2 transistors
No commentsIntro
‘This article covers my experience in converting from rs-232 signal levels to ttl signal levels. I have done it several different ways, there are hard ways and easy ways to do this.
I find myself frequently converting from ttl to rs232 to allow devices using ttl datalevels to communicate with the computer through the rs232 port. And im not archaic in doing so, a lot of devices that we use nowadays still use the same technology, you just dont see it.
What uses rs232 anymore ?
Lots of things plug into the usb port, but somewhere down the line there is a usb to uart or a usb to rs232 converter. I know that on most Microchip ® pic programmers there is a little 32 pin surface mount chip that converts the usb into a serial interface, it has FTDI on it in my case. These are the same type of chips you will find in the “usb to rs232″ cables around. And hidden in lots of devices there is this same “middle man” to allow the same old technology to look new.
If you already know how to plug your own devices into your computers comm port to communicate, just imagine if you buy a “usb to serial” converter for $3 rip the chip out and solder it to your board, then you can connect directly to the usb port. I just use the cable myself, I’m not trying to fool anyone. Anything you plug in via usb that then makes a “virtual serial port” is doing this, also other devices may do this but their drivers dont let you see whats going on.
The Easy way to convert
I have used this adapter before, it works very well and is the best design i have found anywhere. The original maker of this design (great guy!) has a webpage at http://picprojects.org.uk and the actual page for this project can be found at http://picprojects.org.uk/projects/simpleSIO/ssio.htm he has tons of info on how to do lots of neat stuff on that page. I recommend you read it.
This is the circuit.
Simple RS232 conversion
I’m a lazy person, and found that in my case the circuit works without the capacitors. Also i used 2N3904 and 2N3906 transistors in place of the BC ones he has listed in the circuit. I used all surface mount components, here is my finished product.
A harder Way (but better for long distances, or back to back connections)
This solution is much easier than the MAX-232 implementation, I wont even discuss that much here. But if you want a commercial grade product you want to look into the MAX232 chip. It allows two connections to go through it at the same time for a total of 4 devices, but it uses lots of electrolytic capacitors.
What if you are just transmitting one way ?
If you are just converting from uart to rs232 and you dont care about the pic receiving data from the rs232 then you can just use one transistor.
This was much harder to find. There is a guy who like me is just making stuff, this is his page (where i got this info/schematic) http://members.cox.net/berniekm/card.html
He is making a card reader that communicates with the computer via rs232. This is a very good application, turn your computer into a cash register
Of course you dont have to worry about anything except the three wires coming out of the db9 connector. So that amounts to three resistors and a transistor. You should NOTE i could not get this circuit to work until i removed the connection from the tx pin on the db9. So my circuit only connected to the ground and pin2 (the RX pin). Not sure why it didnt work like the schematic, but if yours dont work try unplugging pin 3 on the db9 see if that fixes it.
We used this second design for a lab project, you can read about that here http://zonemikel.com/wordpress/?p=133
Best of wishes, hopefully these simpler designs will result in less time debugging your circuits.