Articles, notes and random thoughts on Software Development and Technology
Add the following to /etc/modules:
i2c-bcm2708 i2c-dev
Install i2c-tools:
sudo apt-get install i2ctools
Edit /etc/modprobe.d/raspi-blacklist.conf and remove/comment out these two lines:
blacklist spi-bcm2708 blacklist i2c-bcm2708
Detect your ic2 interface with:
sudo i2cdetect -y 1 #1 = Pi model B
If you get this error:
Error: Could not open file '/dev/i2c-1' or `/dev/i2c/1': No such file or directory
Then run this first and you should be good to go:
sudo modprobe i2c-dev
More info here.
Key checking on ssh validates that the remote system you’re attempting to connect to is the same server that you connected to the last time, to help prevent the possibility that someone has hijacked the DNS name, IP, or the hardware itself.
However, some times you may want to avoid this checking. For example, I have a Raspberry Pi that I boot from multiple SD cards, but each is setup with the same IP. If strict key checking is enabled then your ssh client will prevent you from connecting when it detects a signature change. You’ll see this error:
RSA host key for 192.168.x.x has changed and you have requested strict checking.
To avoid this, edit or add ~/.ssh/config, and add:
Host 192.168.x.x
StrictHostKeyChecking no
where the IP can be the IP of the machine you’re connecting to, or you can use a * wildcard too (maybe not as secure).
If you’ve already connected and have a key in your known_hosts, then I think you need to delete this entry first, and then try with this config.
A few notes on useful syscalls:
SWI 0 : executes instruction based on value in R7
Write to screen: R7 = 4
MOV R7, #4 @ Syscall 4 = write to screen MOV R0, #1 @ stdout: move 1 to R0 MOV R2, #4 @ length of string to R2 LDR R1, =string SWI 0 string: .ascii "testn"
Read from keyboard: R7 = 3
MOV R7, #3 @ Syscall 3 = read from keyboard MOV R0, #0 @ stdin?: move 0 to R0 MOV R2, #4 @ length of string to ready to R2 LDR R1, =string @ load R1 value to string location SWI 0 string: .ascii ""
JAXB appears to fail silently in some cases if the XML it’s attempting to unmarshall to mapped classes doesn’t have the necessary mapped properties.
You can get additional output by adding the following:
-Djaxb.debug=true
– displays information during JAXB initialization
Before you call unmarshall() on your Unmarshaller, call setEventHandler() and add a DefaultValidationEventHandler as follows:
Unmarshaller um = jaxbContext.createUnmarshaller(); um.setEventHandler(new javax.xml.bind.helpers.DefaultValidationEventHandler());
– this will output additional failure information about missing mappings for xml elements, useful if your mapped class ends up with missing values.