Programming Manual Elektor Proton Robot - ELEKTOR.se

RS232 communication explainedRS-232 (Recommended Standard 232) is the traditional name for a series of standards for serialbinary data and control signals connecting between a processor and peripheral circuits andmachines. It is commonly used in computer serial ports but modern microcontrollers also have oneor more UART’s – capable of communicating with other RS232 devices.RS232 has been used for many years, and in spite of new standards like CAN – RS485 and I2C toname some – is still very popular and widely used.Features:• Uses 2 pins – TX (transmit) and RX (receive) + gnd• Asynchronous – no separate clock signal is transmitted• Asynchronous signals means that transmitter and receiver need exactly the same settings:o Baud rate (1200bps – 9600bps…)o Parity control (yes – no – even – odd)o Stop bits (0-1-2)o Voltage levels (+/-12V or TTL)o Number of data bits (5-6-7-8…9)Most modern microcontrollers have a UART embedded in the controller. This UART - after correctconfiguration – will take care of all the complex timing and other RS232 tasks – in the background.Programmers just need to feed them with data to be sent or read out and clear the receive bufferwhen new data has been received.For microcontrollers without an embedded UART – there is also the possibility to set up a RS232communication – entirely in the software. This is called a bitbanged UART and this is more complexto program and will take more of the resources of the microcontroller away.Bart Huyskens Manual Elektor Proton V1.0 3 April 2011 89