Chapter 8 - Asynchronous communication

Abstract

This chapter reviews the PIC24 asynchronous serial communication interface modules, UART1 and UART2. It develops a small console I/O library while reviewing the basic functionality of the UART module for operation as an RS232 serial port. In addition to the usual software tools, including the MPLAB® IDE, MPLAB C30 compiler and the MPLAB SIM simulator, the chapter requires the use of the Explorer16 demonstration board, the MPLAB ICD2 In-Circuit Debugger and a PC with an RS232 serial port. The UART interface is perhaps the oldest interface used in the embedded-control world. The serial port is declared a “legacy interface” and, for several years now, strong pressure is placed on computer manufacturers to replace it with the USB interface. Despite the decline in their popularity, and the clearly superior performance and characteristics of the USB interface, asynchronous serial interfaces are strenuously resisting in the world of embedded applications because of their great simplicity and extremely low cost of implementation. To demonstrate the basic functionality of a UART peripheral, we will use the Explorer16 demo board where the UART2 module is connected to an RS232 transceiver device and to a standard 9 poles D female connector. This can be connected to any PC serial port or, in absence of the “legacy interface” to an RS232-to-USB converter device. Further the chapter explains using the serial port as a debugging tool.