please dont rip this site

SX Specific FSK Output

Frequency Shift Keying Virtual Peripheral for Telephony applications. This routine provides a 1200 baud, Phase-coherent FSK generation with minimal external circuitry.

Introduction

By combining several virtual peripherals, is possible to provide reception and transmission of asynchronous 1200 bps data using Frequency Shift Keying (FSK) signaling. The resulting software will have uses in a wide range of telephone based information systems.

This application combines PWM, 16-bit timer, and UART virtual peripherals and with a sine lookup table to generate 1200 bps FSK transmission. The UART is used to interface to a PC terminal session at 19.2 Kbps. Any data received by the UART software is sent to the FSK_send routine for transmission. FSK_send first enables the PWM output and external DAA output circuitry and begins to send a 1200 Hz start bit for a duration of 1.5 bits  (1250uS). For data transmission a frequency of 1200 Hz represents the mark and 2200 Hz represents a space. This is immediately followed by the data byte and a stop bit at 2200 Hz. All frequency shifts are phase coherent.

This virtual peripheral relies on an external RC filter to generate the FSK frequencies. A low pass filter is required on the PWM output to create the analog signal as shown in the circuit in figure 1.

The transmission method used is not compliant to any specification. Future revisions will be available to provide compliance to the Bell 202 specification and also to provide FSK demodulation.

Additionally, before this circuit can be connected to any telephone system an appropriate DAA circuit is also required. As seen in the source code, bit three of port A is used to enable the DAA output.

fsk.src
PDF

See also:


file: /Techref/scenix/lib/io/osi1/dfs/fsks.htm, 2KB, , updated: 2001/10/27 13:20, local time: 2017/12/17 23:26,
TOP NEW HELP FIND: 
54.227.126.69:LOG IN

 ©2017 These pages are served without commercial sponsorship. (No popup ads, etc...).Bandwidth abuse increases hosting cost forcing sponsorship or shutdown. This server aggressively defends against automated copying for any reason including offline viewing, duplication, etc... Please respect this requirement and DO NOT RIP THIS SITE. Questions?
Please DO link to this page! Digg it! / MAKE! / 

<A HREF="http://www.piclist.com/techref/scenix/lib/io/osi1/dfs/fsks.htm"> SX Specific FSK Output</A>

After you find an appropriate page, you are invited to your to this massmind site! (posts will be visible only to you before review) Just type in the box and press the Post button. (HTML welcomed, but not the <A tag: Instead, use the link box to link to another page. A tutorial is available Members can login to post directly, become page editors, and be credited for their posts.


Link? Put it here: 
if you want a response, please enter your email address: 
Attn spammers: All posts are reviewed before being made visible to anyone other than the poster.
Did you find what you needed?

  PICList 2017 contributors:
o List host: MIT, Site host massmind.org, Top posters @20171217 RussellMc, Van Horn, David, Sean Breheny, James Cameron, alan.b.pearce, IVP, Neil, Bob Blick, David C Brown, John Gardner,
* Page Editors: James Newton, David Cary, and YOU!
* Roman Black of Black Robotics donates from sales of Linistep stepper controller kits.
* Ashley Roll of Digital Nemesis donates from sales of RCL-1 RS232 to TTL converters.
* Monthly Subscribers: Gregg Rew. on-going support is MOST appreciated!
* Contributors: Richard Seriani, Sr.
 

Welcome to www.piclist.com!

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  .