Quelltext der Seite RFM12 library/en

{{ProjektInfoBox
|name        = rfm12lib
|status      = stable
|image       = Avr_rfm12.png
|description = The rfm12 library provides the ability to use RFM12(B) modules in conjunction with Atmel AVR microcontrollers
|author      = [[Benutzer:Hansinator|Hansinator]], [[Benutzer:Tixiv|Tixiv]], [[Benutzer:Soeren|Soeren]]
|username    = 
|version     = 1.1.0
|update      = 
|platform    = AVR
|license     = GPLv2 or later
|download    = [https://www.das-labor.org/storage/LaborLib/rfm12/ SVN] [http://www.das-labor.org/LaborLibTrac/browser/rfm12 browse]
}}

== Library Features ==

* Basic packet format, including:
** An 8-bit (0..255) packet type or address field
** Packet length up to 255 bytes
** A simple header checksum
* Interrupt or polling based packet transfer handling
* Multiple frequency bands, depending on the used module (433, 868 and 915 MHz)
* Collision avoidance (carrier sense)
* Usage of synchronization patterns to start data reception
* Hardware or software SPI support
* Transmit only mode, to reduce the size of the binary
* Basic ASK (amplitude shift keying) receive and transmit functionality (for radio controlled outlets and the like)
* Low-battery detection feature (using the RFM12)
* Low-power Wakeup timer feature (using the RFM12)


== Documentation ==

Here's the online documentation for version 1.1.0:<br />
http://www.hansinator.de/rfm12lib/

A downloadable version can be found here:<br />
http://www.das-labor.org/files/rfm12lib_doc_1_0_0.zip

== Download ==
The source of version 1.1.0 is available as a downloadable ZIP file [http://www.das-labor.org/files/rfm12lib-1.1.0.zip here] (MD5: 4545ad72782bf9465c1be109ecce9da5).

Alternatively, you could checkout the newest version from our subversion repository. You can [http://www.das-labor.org/LaborLibTrac/browser/rfm12 browse] the repository or directly check out the sources with the command:
  svn co https://www.das-labor.org/storage/LaborLib/rfm12/

== Using the Library ==
The file '''rfm12_config.h''' contains all the configuration as well as a pin assignment table. See the documentation for more info.

Here's an example how to use the library:
 uint8_t teststring[] = "teststring\r\n";
 uint8_t packettype = 0xEE;
 rfm12_init();  /* initialize the library */
 sei();
 
 while (1)
 {
     /* ... */
     rfm12_tx (sizeof(teststring), packettype, teststring);
     rfm12_tick();  /* periodic tick function - call that one once in a while */
 }

== Technical Details ==

=== Collision Prevention ===
Before a packet is actually sent, the RFM12's status register is read in order to measure the current signal strength. When the signal strength is above a treshold, it is assumed that there's a transmission underway. The library then waits some time until the "ether" is free and starts the transmission when the module hasn't seen any traffic for some time.

Collision prevention is enabled by default. You can disable it by defining this '''"#define RFM12_NOCOLLISIONDETECTION 1"''' in your rfm12_config.h.

[[category:Automatisierung]]
[[category:Datenfunk mit dem Microcontroller]]