ASH Transceiver Software Designer's Guide
Updated 2000.12.12
ASH Transceiver Software Designer's Guide 1 Introduction 1.1 Why Not Just Use a UART 1.2 The Radio Channel – Magic and Imperfect 1.2.1 Modeling a radio system 1.2.2 Data rate and bandwidth 1.2.3 Noise and interference 1.2.4 Indoor RF propagation 1.2.5 Regulatory considerations 2 Key Software Design Issues 2.1 2.2 2.3 2.4 Fail-Safe System Design Message Encoding for Robust RF Transmission Clock and Data Recovery Communication Protocols 2.4.1 Digital command transmissions 2.4.2 Data transmissions using packet protocols
3 IC1000 "Radio UART" 3.1 IC1000 Description 3.2 IC1000 Application 4 Example Data Link Layer Protocol 4.1 4.2 4.3 4.4 Link Layer Protocol Source Code Terminal Program Source Variations and Options Test Results
5 Source Code Listings 5.1 5.2 5.3 5.4 DK110X.ASM V110T20A.FRM DK110J.ASM V110T05A.FRM
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6 Disclaimer Drawings Figure 1.2.1 Figure 1.2.2 Figure 1.2.3.1 Figure 1.2.3.2 Figure 1.2.3.3 Figure 1.2.3.4 Figure 1.2.3.5 Figure 2.2.1 Figure 2.2.2 Figure 2.4.1 Figure 3.2.1 Figure 4.1 Figure 4.2 Figure 4.3 Figure 4.4 Radio System Model Receiver Signal Processing Noise Amplitude Probability Distribution Signal Reception with No Noise Signal Reception with Moderate Noise Signal Reception with Heavy Noise Reception with Heavy Noise (expanded scale) Noise Reception with No Signal and No Threshold Signal Reception with No Signal and Moderate Threshold ASH Receiver Application Circuit – Keyloq Configuration Typical IC1000 Application ASH Transceiver Application Circuit – Low Data Rate OOK Radio Board Modification Detail Jumper Pin Detail Packet and Byte Structure Details
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1 Introduction
1.1 Why Can't I Just Use a UART Why can't I just use a UART and a couple of transistors to invert the TX and RX data signals to and from your ASH transceiver and get my application on the air Well, you can if you don't need maximum performance and you make the necessary provisions in your software for the characteristics of radio communications. But, you are going to leave a lot of performance on the table. A radio link is a type of communication channel, and it has specific properties and characteristics, just as an ordinary phone line is another type of communication channel with its own properties and characteristics. To get usable data communications over your phone line, you place a modem between your PC's UART and the phone line. And to get good performance from your ASH radio link, you are going to need to put something more than a couple of transistors between the UART and the transceiver. 1.2 The Radio Channel – Magic and Imperfect Radio is magic. It allows commands, data, messages, voice, pictures and other information to be conveyed with no physical or visible connection. A radio wave can penetrate most materials, and it can get around most barriers it cannot directly penetrate. It is arguably the most useful electronic communication channel so far discovered. But from a software developer's point of view, a radio channel has some aggravating properties and characteristics. The good news is there are strategies for dealing with them. 1.2.1 Modeling a radio system Figure 1.2.1 is a block diagram of a radio system. The antenna on the transmitter launches energy into the RF channel, and the antenna on the receiver retrieves some of the energy and amplifies it back to a useful level. No big deal, right Well its no small deal either.

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