Monday, March 24, 2014

xbee notes

Nice page with list of things you can do wrong

High power xbee 

Xbee Pro 868

With XBee-PRO 868 you have 40 km within reach

If you´re searching for an RF communication module with a long range, you´re on the right address. More precisely said – 40 km at line-of-sight outdoor, or 550m indoor.
XBee technology enables to transfer data from various sources, mainly in industry – for example data from various sensors, controlling of technology and similar. XBee-PRO 868 from DIGI International (Maxstream) uses SRD G3 868 MHz band (869,525 MHz) and has a software selectable output power in the 1 - 315mW range.

Advantages / Features:

  1. powerful XBee module
  2. simple to use topology
  3. line-of sight range up to 40 km (outdoor) / 550m indoor and in urban conditions
  4. 1 to 315 mW (0 až +25 dBm) output RF power
  5. receiver sensitivity: -112 dBm
  6. 24kbps RF data rate
  7. AES 128 bit data encryption
  8. 16 bit network ID
  9. low power consumption 3,3V/65-500 mA
  10. footprint common with other XBee modules types
Relatively high maximum output power provides to the module a very long range. This enables to use it in applications with long distances between particular points. XBee_PRO can be connected to your application via a standard 3.3V CMOS UART with 1.2 to 230.4 Kbps data rate. Various XBee modules from Digi International feature common footprint, that´s why they´re mutually exchangeable this adaptable to your application requirements. XBee-PRO 868 features 128 bit AES encryption and a 64 bitovou adress (network ID). They are usable for Point-to-Multipoint/Star or also Peer-to-peer topologies. An advantage is also an easy use - no further configuration is necessary. Available are multiple versions, type XBP08-DPSIT-024 has an RPSMA connector. Thanks to it, the module can be connected to various antennas.

Detailed information will provide you the XBP08-DPSIT-024 datasheet, overview of XBee-PRO 868 modules, as well as XBee/RF family comparison from company Digi International. In case of interest, please contact us at

Xbee to wireshark article

Sunday, March 23, 2014

Simple method of mounting SD card image partitions for testing

Frequently you will have an SD card with linux or other partitions and you will require a method to access them.

In the case of the shell script here, I had to dd images of sd cards and I wanted to start out with just diffing everything on the two cards at a file level

First you need to fdisk the image and get the offset of the partitions you need to get to.

then perform a mount -loop,option with an offset to the start of the partition.

If you are lucky, you won't need to specify an FS type as the mount software will figure that out.

root@jws2:/home/jws/work/pitbull2# cat

#root@jws2:/home/jws/work/pitbull2# fdisk ipfire-72-pitbull.img
#Command (m for help): p
#Disk ipfire-72-pitbull.img: 15.7 GB, 15719727104 bytes
#64 heads, 32 sectors/track, 14991 cylinders, total 30702592 sectors
#Units = sectors of 1 * 512 = 512 bytes
#Sector size (logical/physical): 512 bytes / 512 bytes
#I/O size (minimum/optimal): 512 bytes / 512 bytes
#Disk identifier: 0x00000000
#                Device Boot      Start         End      Blocks   Id  System
#ipfire-72-pitbull.img1   *          32      131071       65520    c  W95 FAT32 (LBA)
#ipfire-72-pitbull.img3          131072    30701567    15285248   83  Linux

mount -o loop,offset=$((131072 * 512)) ipfire-72-pitbull.img /mnt/reference/
mount -o loop,offset=$((131072 * 512)) mmcblk0.backup.compress /mnt/test/

diff -u -r /mnt/reference /mnt/test > diffout.txt

This illustrates not only the mount method but also the diff method.

The two images are both 16gb SD card image files.  You would also have to create the files in /mnt, or some other location upon which to mount the images.

Reference on loop mounting: