I am not using the EVM, but I have designed the 803 into a temperature controller. I am using all 8 A/D channels to read RTD inputs. Consecutive readings typically within +/- 1 count. On your EVM, are you using the ADref to power the potentiometer? If not, any variations in the power supplies will affect your A/D result. When you testing using the battery, if the ADref power supply is fluctuating, you will get noisy A/D results. The three LSB's of the AD result registers are always zero. Is the result shown by PC_MASTER right shifted so that you only get 12 bits? If not, your readings may really only be bouncing by 5 counts. On other projects, I often use an Olympic or median window filter. Each cycles, I take one new sample plus the preivoud five, throw out the highest and lowest of the six, and average the remaining four. Ending up with 4 (or 8) samples makes the math faster on most processors. This filter works well when popcorn noise causes an occasional wild reading in an otherwise stable signal. Sheldon Black RiboTech, Inc. 9484 Chesapeake Dr. Suite #807 San Diego, CA 92123 (858) 571-1235 (858) 571-1226 fax ----- Original Message ----- From: To: Sent: Friday, October 25, 2002 1:43 AM Subject: [motoroladsp] ADC signal noise in EVB Hi All, I have tried to use ADC in DSP56F805 EVM with SDK application note "ADC" and I have modified it to view result of conversion with PC-MASTER. I have connected a potentiometer to drive AN1 in J9 (A/D connector) but the result is that the readed value has an oscillation range of 40 bits. After, I tried to connect a 3.6V battery with a divider resistor network by 2 and the result has been the same. Is this high signal noise normal? How can I reduce the noise to obtain a good value read ? Thanks --------\ -------- Marco Pellizzaro QEM srl S.S. 11 Km 339 LocalitSignolo 36054 Montebello Vic.no - VI - ITALY Phone +39-0444-440061 Fax. +39-0444-440229 e-mail: http://www.qem.it --------\ -------- _____________________________________ Note: If you do a simple "reply" with your email client, only the author of this message will receive your answer. You need to do a "reply all" if you want your answer to be distributed to the entire group. _____________________________________ About this discussion group: To Join: To Post: To Leave: Archives: http://www.yahoogroups.com/group/motoroladsp More Groups: http://www.dsprelated.com/groups.php3 |