====== Communication with the CAN bus ====== This topic handles about exchanging data with a CAN bus system by using the SPI interface of the Carambola 2 device. Additional to the Carambola it's necessary to build a hardware circuit with the [[http://ww1.microchip.com/downloads/en/DeviceDoc/21801e.pdf|MCP2515]] (CAN controller) and the [[http://ww1.microchip.com/downloads/en/DeviceDoc/21667f.pdf|MCP2551]] (CAN transceiver) from [[http://www.microchip.com/|Microchip]]. This article is a summary of To-Do actions paired with the patches released by forum user Gerd. Big thanks for your enormous help! ====== Hardware ====== This chapter handles the hardware connection of the Carambola 2 with the 2-wire CAN bus. ===== CAN bus ===== Please catch the information out of the Wikipedia page: [[http://en.wikipedia.org/wiki/CAN_bus|HERE]] The topic is much too complex to explain everything in here. ===== SPI bus ===== The SPI bus is a full-duplex and serial bus system with maximum speed of 11 MHz. It is a single master bus system where every slave must have a single connection to the master, the Chip Select (or Slave Select). The following lines are required to build a complete SPI bus system: * SPI-CLK (Clock, common line) * SPI-MISO (Data, Master In Slave Out, common line) * SPI-MOSI (Data, Master Out Slave In, common line) * SPI-CS (Chip Select, one line per slave, outgoing from the bus master) The master initiates a data exchange by selecting a slave chip by enabling the SS-Pin for the appropriate slave. Further, the master begins to clock the SPI-CLK line to syncrhonize with the slave. On each Clock the Master is able to send a bit information to the slave over the MOSI-line. Coincident the slave can provide information to the master over the MISO line. After the transmission the SS-pin is disabled and the slave stops sending. ===== Hardwarelayout with the MCPs =====