DSP interface program for the VE2IQ COHERENT program. Version 1.1 -------------------------------------------------------- These notes are not complete; if you are not comfortable at building interfaces yourself and able to load software into the EVM, please get some help first. I am afraid these notes will not be sufficient for beginners, but there are several talented folks on the DSP net than can help - just ask. To get started with this BPSK project, obtain COHERENT from http://www.ietc.ca/home/bill/bbs.htm. Read Bill DeCarle's notes. To start the EVM side of things, a couple of helpful hints. 1) Change the EVM's ceramic resonator for a 4 MHz crystal. I have one EVM that has a real crystal in a metal can package, and another that has a blue three-legged resonator. The crystals are good - no need to change those. 2) COHERENT interfaces to the real world through a COM port. It receives digitized data at 115,200 BPS, and the characters are transmitted at a rate of 7200 per second, so make sure that your computer's serial port can handle this. In addition, PSK signaling is done by changing the state of the RTS line. If you wish, PTT control can be derived from the DTR line. The usual published interfaces on the TAPR web site for interfacing to the SCI port usually does not include any connections to the RTS and DTR lines - you would need to add this. The way I did this was to add a pair of RS232-to-TTL convertors on the EVM interface that change the RTS and DTR signals (on the SCI port only.) These level shifters can be someting really simple. I connect the RS232 line in question to a 10K series resistor feeding into the base of a 2N2222 or 2N3904 transistor. The base of the transistor is then protected by a 1N914 diode (cathode to the transistor base, anode to ground). The transistor emitter is grounded, and the collector is then taken via a 1K resistor to +5V. I then routed wires from the collector of each transistor to PB8 and PB9 corresponding to RTS and DTR respectively. 3) Notice that the RED LED will serve as your input overload indicator - it has been arranged that input overload at the EVM corresponds to the "CLIPPING" level for COHERENT. 4) The GREEN LED flashes at 1 second intervals. When you get your code loaded and running, check the accuracy of your EVM against the second ticks on WWV. It should hold time even for extended periods, however, if you can hold time for a few minutes, you are marginal, but it will work. If not, read the bit about replacing the ceramic resonator. 5) The rest is easy: load the BPSK.CLD file into the EVM using your EVM debugger, and GO 0. This program does not work with BIOS so no need to load that. You should see the green "heartbeat" flashing at 1s rate. Switch RS-232 ports to the SCI port, and first try the VE2IQ, FFTZZ program. If all is well, that should run, else you have something not working right. If you are ready, run COHERENT - take a few minutes to set up the command line arguments. Conventionally, you would want to use MS25, with ET off. Important too to make sure that you specfy the correct COM port. 6) If you place a RS-232 state monitor (available from Radio Shack) in line at the EVM, you will see that RTS is pulsing on/off. This tells us that COHERENT is up and running and is sending phase change requests to the EVM. Also note that DTR is like a keyboard VOX, controlled by the "MUTE" option. If you have MUTE=off, then you can switch back from transmit to receive by typing a "#" character. Note the use of the "END" key to start synchronizing, and the use of the "TAB" key to send sinchronization characters. 7) As a beginner - be forewarned that COHERENT takes a bit to get used to - so be patient and ask when you need help. Good Luck! Enjoy. Disclaimer: ----------- This program is provided "as is" and is intended for educational purposes only. The author(s) cannot be held resonsible for any mishap or accident resulting through the use of this software. --Use at your own risk-- This software is not to be used for any commercial application, military or government agencies without explicit written approval from author(s). Acknowledgements: ------------------ I am indebted to Pawel Jalocha, SP9VRC for many pieces of this code. Bill DeClarle, VE2IQ helped and assistance is appreciated. Thanks to Cliff Buttschardt, K7RR, and Bill Lake, WB6RIJ for the many wonderful QSO's and being patient elmers. Johan B. Forrer, KC7WW 26553 Priceview Drive, Monroe, OR 97456, USA July, 1997.