EVAL-315-KH2

EVAL-315-KH2 EVAL-418-KH2 EVAL-433-KH2 WIRELESS MADE SIMPLE ® KH2 SERIES BASIC EVALUATION KIT USER’S GUIDE ORDERING INFORMATION PART # DESCRIPTION EVAL-***-KH2 KH2 Series Basic Evaluation Kit *** = 315, 418 (Standard), 433MHz INTRODUCTION Linx KH2 Series RF modules offer a simple, efficient, and cost-effective method of adding wireless communication capabilities to any product. The basic Evaluation Kit is intended to give a designer all the tools necessary to correctly and legally incorporate the KH2 Series modules into an end product. The development boards themselves serve several important functions: • Rapid Module Evaluation - The boards allow the performance of the Linx KH2 Series modules to be evaluated quickly in a user’s environment. • Range Testing - Using the on-board encoders and decoders to generate a simplex transmission, a pair of development boards can be used to evaluate the range performance of the modules. • Design Benchmark - During the design process of your product, the boards provide a known benchmark against which the performance of your own design can be judged. • Application Development - An on-board prototyping area is provided to allow a designer to develop applications directly on the development board. All signal lines are available on a breakout header for easy connection to the designer’s circuits. The purpose of this guide is to show the designer how to take full advantage of the basic development boards included with the kit. The kit includes 2 KH2 Series transmitters*, 2 KH2 Series receivers*, 2 extra PCBmount RP-SMA connectors, 2 development boards, 2 CW Series antennas, 1 CR2032 battery, 2 AAA batteries, and full documentation. *One part is soldered to the board, one extra for use on your first prototype board. Revised 11/17/11 KH2 TRANSMITTER EVALUATION BOARD THEORY OF OPERATION TRANSMITTER EVALUATION BOARD The transmitter board is powered by an on-board 3V CR2032 lithium battery. It has eight SPST pushbutton switches, the state of which are encoded into a data stream by the module. If a switch is closed, the module will capture the settings of the 10-position DIP switch address bits and pushbutton states for encoding and transmission. The transmitter will transmit continuously when any switch is closed or when Transmit Enable (TE) is pulled high. This board has a prototyping area with all of the transmitter lines brought out to a header for easy access by external circuitry. 7 5 4 3 1 8 6 9 The receiver board is powered by two AAA batteries. The KH2 Series receiver exhibits a sensitivity of greater than -112dBm, so under optimum line-of-sight conditions, the transmitter / receiver link can operate over distances of up to 3,000 feet. The data recovered by the KH2 Series receiver is internally decoded. If the settings of the 10-position DIP switch on the receiver board match the address setting of the transmitter board, the data lines are updated to match the state of the data lines (or pushbuttons) on the transmitter board. To demonstrate this, one data line is used to drive a LED while another is used to activate a buzzer. Switching transistors are used as drive buffers because the KH2 receiver cannot directly source the current necessary to operate these devices. This board has a prototyping area with all of the receiver lines brought out to a header for easy access by external circuitry. 2 1. 2. 3. 4. 5. 6. 7. 8. 9. Battery - 3VDC (use a CR2032-style battery only) Power Switch Momentary Pushbutton - S0 (D0) Momentary Pushbutton - S1 (D1) Continuous Transmit Switches Prototyping Area Reverse-Polarity SMA Antenna Connector KH2 Series Transmitter Module 10-Position Address DIP Switch USING THE KIT KH2 RECEIVER EVALUATION BOARD 2 Using the kit is straightforward. Simply attach the antennas, turn on the power, and press one or both of the buttons on the transmitter board. When S0 is pressed, the buzzer will sound; when S1 is pressed, the LED will turn on. 3 7 4 1 6 5 RECEIVER EVALUATION BOARD 8 DEVELOPMENT USING THE PROTOTYPING AREA In addition to their evaluation functions, the boards may also be used for actual product development. They feature a prototyping area to facilitate the addition of application-specific circuitry. This area has a connection to VCC at the top and ground at the bottom that can be used to power the added circuitry. NOTE: The CR2032-style battery on the transmitter board has very low current capacity, with only about 3mA available for external circuitry. If added circuitry requires a higher current, the battery must be removed and the board powered from an external source. The holes are plated and set at 0.100” on center with a 0.040” diameter, making it easy to add most industry-standard SIP and DIP packages to the board. 1. 2. 3. 4. 5. 6. 7. 8. Page 2 Battery - 3VDC (use 2 AAA style batteries only) Power Switch Buzzer - D0 LED - D1 Prototyping Area KH2 Series Receiver Module Reverse-Polarity SMA Antenna Connector 10-Position Address DIP Switch On the transmitter board, the data lines and the TE line from the encoder have been wired out to a header on the right side of the prototyping area. On the receiver board, the data lines from the decoder plus the PDN, and DATA lines from the receiver have been wired out. This allows for easy access to connect external circuitry to the modules, the encoder, and the decoder. Data line D0 is connected to the buzzer and D1 is connected to the LED. Page 3 RANGE TESTING Several complex mathematical models exist for determining path loss in many environments. These models vary as the transmitter and receiver are moved from indoor operation to outdoor operation. Although these models can provide an estimation of range performance in the field, the most reliable method is to simply perform range tests using the transmitter and receiver in the intended operational environment. Simple range testing can be performed with the transmitter and receiver evaluation boards. To prepare the board for range testing, ensure that the address line DIP switches on both boards are identically set. Turn on the boards by switching the power switch to the ON position. Pressing S0 on the transmitter will activate the buzzer on the receiver board, while S1 activates the LED. Sliding switch SW0 or SW1 to the right will cause the transmitter to continiously transmit. This will allow the designer to turn on the transmitter and walk with the receiver. As you near the maximum range of the link in your area, it is not uncommon for the signal to cut in and out as you move. This is normal and can result from other interfering sources or fluctuating signal levels due to multipath effects. This results in cancellation of the transmitted signal as direct and reflected signals arrive at the receiver at differing times and phases. The areas in which this occurs are commonly called “nulls” and simply walking a little farther will usually restore the signal. Since the evaluation boards are intended for use by design engineers, they are not FCC certified. The transmitter has been set to approximate legal limits by resistor R1 so that the range test results will approximate the results from a welldesigned, certified product. For applications where Part 15 limits are not applicable or output levels can be legally raised due to protocol duty cycle, R1 can be changed according to the graph on Page 3 of the KH2 Series Transmitter Data Guide. To achieve maximum range, keep objects such as your hand away from the antenna and ensure that the antenna on the transmitter has a clear and unobstructed line-of-sight path to the receiver board. Range performance is determined by many interdependent factors. If the range you are able to achieve is significantly less than specified by Linx for the products you are testing, then there is likely a problem with either the board or the ambient RF environment in which the board is operating. First, check the battery, jumper routing, and antenna connections. Next, measure the receiver’s RSSI voltage with the transmitter turned off to determine if ambient interference is present. If this fails to resolve the issue, please contact Linx technical support. ABOUT ANTENNAS The choice of antennas is one of the most critical and often overlooked design considerations. The range, performance, and legality of an RF link are critically dependent upon the type of antenna employed. Linx offers a variety of antenna styles that you may wish to consider for your design. Included with your kit is a Linx CW Series connectorized whip antenna that should be connected prior to using the kit. Despite the fact that the antenna is not centered on the board’s ground plane, it exhibits a VSWR of