RS485 Transceiver Component

Transcription

1 RS485 Transeiver Component Publiation Date: 2013/3/25 XMOS 2013, All Rights Reserved.

2 RS485 Transeiver Component 2/12 Table of Contents 1 Overview 3 2 Resoure Requirements 4 3 Hardware Platforms Reommended Hardware Sliekit Demonstration Appliations RS485 Terminal Console Demo (app_rs485) API Configuration Defines RS485 API RS485 Funtion Configuration Funtions Transmit Funtions Programming Guide Key Files Initialising the Interfae Demo Appliations app_rs Makefile rs485_onf.h Top level program struture app_rs485_demo Makefile rs485_onf.h ommon.h Top level program struture

3 1 Overview This module implements a half-duplex RS485 UART with diretion ontrol. Integer baud rates up to 1 Mbps are supported along with one or two stop bits, 7, 8 or 9 data bits, and odd/even/no parity. The omponent an sustain 1Mbps in a single 62.5MIPS thread.

4 2 Resoure Requirements Resoure Usage Memory 1.5K Channelends 2 Timers 1 Clokbloks 0 Logial Cores 1 1-Bit Ports 1 4-Bit Ports 1* 1 bit of a 4-bit port is used for diretion ontrol. This an easily be moved to a 1-bit port should a 4-bit port not be available.

5 3 Hardware Platforms IN THIS CHAPTER Reommended Hardware Demonstration Appliations 3.1 Reommended Hardware Sliekit This module may be evaluated using the Sliekit Modular Development Platform. Required board SKUs are: XP-SKC-L2 (Sliekit L2 Core Board) plus XA-SK-XTAG2 (Sliekit XTAG adaptor) XA-SK-ISBUS (SlieKit Industrial Serial Bus Slie) 3.2 Demonstration Appliations RS485 Terminal Console Demo (app_rs485) This demostration appliation requires the three RS485 onnetions (A,B and GND_ISO) to be onneted to an appropriate USB to RS485 onverter (eg. Amplion USB-485Ui) onfigured in half-duplex mode with no loal eho. A serial terminal program on a PC an then be used to send and reieve the ehoed data.

6 4 API IN THIS CHAPTER Configuration Defines RS485 API 4.1 Configuration Defines The file rs485_onf.h an be provided in the appliation soure ode, without it the default values speified in rs485.h will be used. This file an set the following define: RS485_BUF_SIZE This define sets size of the reeive data buffer. 4.2 RS485 API RS485 Funtion void rs485_run(hanend _ontrol, hanend _data, rs485_interfae_t &rs485_if, rs485_onfig_t &rs485_onfig) Implemetation of a half-duplex RS485 interfae. This funtion requires an unbuffered 1-bit port for the bi-diretional RS485 data hannel, and one bit of a 4-bit port to set the data diretion. Setting the diretion bit low will put the hannel in to reeive mode, and setting high will put it in transmit mode. The funtion also requires two hannels, one for ontrol and the other for reeived data. The ports to be used are speified in the rs485_interfae_t strut and then passed in. The default state of the hannel is to go into reeive mode and wait for a start bit. One reeption has started a timeout is set, the timeout is reset for eah data byte reeived. On expiration of the timeout (no data reieved in the elapsed time) the reeived paket is transferred via the data hannel. The parameters that may be set in this way are: The operating parameters (stop bits, data bits, parity and baud) an be hanged using ommands on the ommand hannel, and are initially set in the rs485_onfig_t_ strut and then passed in. On a 62.5 MIPS ore this funtion shold be able to support 1 Mbps transmission rate.

7 RS485 Transeiver Component 7/12 This funtion does not return. _ontrol _data rs485_if rs485_onfig The ontrol hannel The data hannel for reeived data The IO pins for data and diretion The initial onfiguration of the omponent Configuration Funtions int rs485_set_baud(hanend, int baud) Set the baud rate. Sets the baud rate of the RS485. Only whole integer numbers are supported. The ommand interfae hannel baud The baud rate (bps) int rs485_set_data_bits(hanend, int data_bits) Set the number of data bits. Sets the number of data bits for the RS485. Only whole integer numbers are supported. The ommand interfae hannel data_bits The number of data bits int rs485_set_stop_bits(hanend, int stop_bits) Set the number of stop bits. Sets the number of stop bits for the RS485. Only whole integer numbers are supported. The ommand interfae hannel stop_bits The number of stop bits int rs485_set_parity(hanend, rs485_parity_t parity) Set the parity.

8 RS485 Transeiver Component 8/12 Sets the parity option for the RS485. The ommand interfae hannel parity The parity option, type rs485_parity rs485_state_t rs485_get_status(hanend ) Get the urrent status. Returns the urrent status of the RS485. Will return one of rs485_state The ommand interfae hannel Transmit Funtions int rs485_send_byte(hanend, unsigned har data) Transmit one byte. Transmit a single byte MSB first Return 0 if TX is not possible, 1 if TX suessful The ommand interfae hannel data The byte to transmit int rs485_send_paket(hanend, unsigned har data[], unsigned len) Transmit speified number of bytes. Most signifiant bit first order. Big endian byte order. Return 0 if TX is not possible, 1 if TX suessful data len The ommand interfae hannel The array of data to transmit The number of bytes to transmit, this must not be greater than the size of buffer

9 5 Programming Guide IN THIS CHAPTER Key Files Initialising the Interfae 5.1 Key Files The rs485.h header file ontains prototypes of all funtions required to use use the RS485library. No other header files need to be inluded in the appliation. The API is desribed in Initialising the Interfae The interfae is initialised and run using the rs485_run funtion.

10 6 Demo Appliations IN THIS CHAPTER app_rs485 app_rs485_demo 6.1 app_rs485 This appliation uses module_rs485 to reeive data from an RS485 hannel, and ehoes the data bak on the same hannel Makefile The Makefile is found in the top level diretory of the appliation. The appliation is for the Sliekit Core Board so the TARGET variable needs to be set in the Makefile as: TARGET = XK -SKC -L rs485_onf.h The rs485_onf.h file is found in the sr/ diretory of the appliation. This file ontains a #define that onfigures the RS485 omponent. The possible #define that an be set is desribed in 4.1. If not set, default values in the rs485 header file will be used. Within the demo appliation set the reeive data buffer is set to 128 haraters. // Copyright () 2011, XMOS Ltd., All rights reserved // This software is freely distributable under a derivative of the // University of Illinois / NCSA Open Soure Liense posted in // LICENSE. txt and at <http :// github. xore. om /> /*=========================================================================== Filename : rs485_onf.h Projet : app_rs485 Author : XMOS Ltd Version : 1v */ # ifndef RS485_CONF_H_

11 RS485 Transeiver Component 11/12 # define RS485_CONF_H_ # define RS485_BUF_SIZE 128 # endif /* RS485_CONF_H_ */ Top level program struture This appliation is ontained in app_rs485.x. Within this file is the main() funtion whih runs the example appliation funtion, that takes the reeived data and sends it bak out, and the RS485 server funtion. To make use of the RS485 funtion library the app_rs485.x must ontain the following line: # inlude " rs485.h" The RS485 interfae is initialsied to operate at 9600 baud, 8 data bits, 2 stop bits and a 10 harater timeout. When a paket of data is reieved it is passed to the appliation funtion via the data hannel, and is then transmitted as a paket using the rs485_send_paket funtion. 6.2 app_rs485_demo This appliation uses module_rs485 and demonstrates the usage module_rs Makefile The Makefile is found in the top level diretory of the appliation. The appliation is for the Sliekit Core Board so the TARGET variable needs to be set in the Makefile as: TARGET = XK -SKC -L rs485_onf.h The rs485_onf.h file is found in the sr/ diretory of the appliation. This file ontains a #define that onfigures the RS485 omponent. The possible #define that an be set is desribed in 4.1. If not set, default values in the rs485 header file will be used. Within the demo appliation set the reeive data buffer is set to 128 haraters.

12 RS485 Transeiver Component 12/ ommon.h The ommon.h file is found in the sr/ diretory of the appliation. This file ontains a #define that onfigures the RS485 omponent settings suh as Baud rate, parity, data bit length. The possible #define that an be set is desribed in 4.1. If not set, default values in the rs485 header file will be used. Within the demo appliation set the reeive data buffer is set to 128 haraters Top level program struture This appliation is ontained in app_rs485_demo.x. Within this file is the main() funtion whih runs the example appliation funtion, that takes the reeived data and sets the paramater settings for the RS485 server funtion. To make use of the RS485 funtion library the app_rs485_demo.x must ontain the following line: # inlude " rs485.h" The RS485 interfae is initialsied to operate at 9600 baud, 8 data bits, 2 stop bits and a 10 harater timeout. This information an be hanged in ommon.h header file. Copyright 2013, All Rights Reserved. Xmos Ltd. is the owner or liensee of this design, ode, or Information (olletively, the Information ) and is providing it to you AS IS with no warranty of any kind, express or implied and shall have no liability in relation to its use. Xmos Ltd. makes no representation that the Information, or any partiular implementation thereof, is or will be free from any laims of infringement and again, shall have no liability in relation to any suh laims. XMOS and the XMOS logo are registered trademarks of Xmos Ltd. in the United Kingdom and other ountries, and may not be used without written permission. All other trademarks are property of their respetive owners. Where those designations appear in this book, and XMOS was aware of a trademark laim, the designations have been printed with initial apital letters or in all apitals.