RS485 board datasheet EB062-00 00-1 Contents 1. About this document... 2 2. General information... 3 3. Board layout... 4 4. Testing this product... 5 5. Circuit description... 6 Appendix 1 Circuit diagram Copyright Matrix Multimedia Limited 2010 page 1
1. About this document This document concerns the E-blocks RS485 board code EB062 version 1. The order code for this product is EB062. 1. Trademarks and copyright PIC and PICmicro are registered trademarks of Arizona Microchip Inc. E-blocks is a trademark of Matrix Multimedia Limited. 2. Other sources of information There are various other documents and sources that you may find useful: Getting started with E-Blocks.pdf E This describes the E-blocks system and how it can be used to develop complete systems for learning electronics and for PICmicro programming. PPP Help file This describes the PPP software and its functionality. PPP software is used for transferring hex code to a PICmicro microcontroller. C and assembly strategies This is available as a free download from our web site. 3. Disclaimer The information in this document is correct at the time of going to press. Matrix Multimedia reserves the right to change specifications from time to time. This product is for development purposes only and should not be used for any life-critical application. 4. Technical support If you have any problems operating this product then please refer to the troubleshooting section of this document first. You will find the latest software updates, FAQs and other information on our web site: www.matrixmultimedia.com Copyright Matrix Multimedia Limited 2010 page 2
2. General information 1. Description This E-block provides an RS485 interface that can be used to facilitate communication between a microcontroller and third party devices like communications systems or industrial sensors etc. Flowcode macros for driving this E- block are available via the RS232 component or simply the I/O icons depending on your application. A set of jumper links are available which allow the RS485 E-block to easily be set for all microcontroller port configurations. Flowcode macros that make this device easier to use are available. 2. Features E-blocks compatible 1 full duplex RS485 connection 2 half duplex RS485 connection Data rates up to 16Mbps Up to 256 transceivers per bus 3.3V compatible (if alternate driver chips are retro-fitted) 3. Block diagram Copyright Matrix Multimedia Limited 2010 page 3
3. Board layout EB062-74-1.cdr 1) 9-way downstream D-type connector 2) Patch system 3) +V screw terminal 4) Transceiver data channel allocation 5) Transceiver data direction control 6) RS485 transceiver IC 7) RS485 termination control 8) RS485 bias control 9) RS485 level screw terminals General guide for patch settings: Jumper A Jumper B Jumper C (Patch) CH1 Signal BIT5 BIT6 PATCH CH2 Signal BIT2 BIT7 PATCH DDR1 Signal BIT0 BIT0 PATCH DDR2 Signal BIT1 BIT1 PATCH Copyright Matrix Multimedia Limited 2010 page 4
4. Testing this product The following program will test the circuit. The test file can be downloaded from www.matrixmultimedia.com. 1. System Setup Multi-programmer board (EB006) with: EB006 Options Power supply PICmicro device SW1 (Fast/Slow) SW2 (RC/Xtal) Xtal frequency Port A Port B Port C Port D Port E Test program EB005 Options Patch jumper setting EB060 Options Patch jumper setting CH1 CH2 DDR1 DDR2 BIAS Jumpers Termination Jumpers Setting External, 14V 16F877A Don t care Xtal 19.6608MHz LCD board EB005 RS485 board EB062 EB062_Test.hex Setting DEFAULT Setting B TX1 (J16) RX2 (J19) IO (J6) IO (J10) On Position On Position The EB062_Test.hex program will use a loop back method to test that data can correctly flow in and back out of the RS485 board. The LCD will show the status of the testing and confirm if your board has passed or failed testing. 2. Test Procedure 1. Setup the system as shown above. 2. Wire a connection from the +v terminal on the Multiprogrammer to the +V terminal on the EB062. 3. Wire a connection from the +v terminal on the Multiprogrammer to the +V terminal on the EB005. 4. Wire a connection from the A position of terminal J3 to the A position of terminal J7. 5. Wire a connection from the B position of terminal J3 to the B position of terminal J7. 6. Power up the Multiprogrammer by connecting the power supply. 7. Send the EB062_Test.hex program to the 16F877A device on the EB006 multiprogrammer. 8. The LCD will indicate that the testing is being performed and then give an indication of pass or fail depending on the outcome of the test. Copyright Matrix Multimedia Limited 2010 page 5
5. Circuit description The design of this product enables you to use this device with many standard microcontroller devices. This is achieved by identifying the pins on the PICmicro, then by selecting the corresponding jumper setting on the RS485 board. This will allow you to configure the correct pin-out for any microcontroller device. 1. Data Direction Control The data direction control jumpers allow for the two transceiver modules to be put into receive or transmit mode. A single transceiver cannot send and receive data at the same time. For bi-directional communications you can either set up one transceiver to be a receiver and the other a transmitter or you can use the IO settings and control the data direction using an output pin from the upstream microcontroller. Using this method up to two bi-directional halfduplex communications busses can be created using a single RS485 E-block. 2. Channel Selection The channel selection jumpers control the assignment of the data pins to functions on the transceiver chips. This can be used to assign both channels as inputs or outputs or one of each type to allow full duplex communications. 3. Termination and Biasing The termination control jumpers select if a terminating resistor is placed across the RS485 data lines. The termination resistor is required for RS485 nodes that are on the end of a bus or where data reflections need to be attenuated and minimized. Similarly the bias control jumpers select if pull up and pull down resistors are placed onto the RS485 data lines. These resistors can be used to help maintain voltage separation on the active data lines. 4. RS485 signals explained RS485 is often used as it can be used effectively over long distances and in electrically noisy environments. Multiple transceivers may be connected to a RS485 network in a linear or multi drop configuration. The signal is a differential signal and is sent along twisted pair wire to help retain noise immunity. The bus should be created as a single line of nodes with termination resistors fitted at each end and should not be connected into star or ring topologies. RS485 Signal Diagram 5. 3.3V operation This board comes with 5V driver chips fitted as standard. RS485 by standard is a 5V bus. A 3.3V version of the driver chip is available and can be used to provide 3.3V functionality by replacing the two 75176 driver chips with MAX3078 driver chips. Copyright Matrix Multimedia Limited 2010 page 6
Appendix 1 Circuit diagram