I normally get a reading of about +/- 2 counts on my A2D conversions on the 16F876. Dont forget if you set ADCON1 to left justify, you still only have 1023 counts max, the last 6 digits are always zero. Its just different in the way the data is presented (10 bit A2D converter). ----- Original Message ----- From: To: Sent: Tuesday, December 02, 2003 11:15 PM Subject: PIC16F87X ADC channels > For some time I've felt that the ADC on the PIC16F87X were not really stable, > so todau I decided to find out. > > Using a 16F877 I applied a DC voltage to PortA.1. I set ADCON1 for left > justify - 65535 count max - and the count was jumping from 100 to 200 counts. I > reset ADCON1 to right justify - 1023 counts max - and the count was jumping > about four. This is equivalent to a fluctation of about 20mv. > > I performed the same test with a 12-bit TLC2543 - 4095 counts max - and the > count was absolutely rock steady. I checked both ADC voltage inputs with my > Optascope and there was no difference in either case. > > 20mv doesn't sound like much but when you are trying to control the ADC > output to plus or minus 5mv it's a bunch. > > Has anyone else noticed this problem? > > Sid > > -- > http://www.piclist.com hint: To leave the PICList > mailto:piclist-unsubscribe-request@mitvma.mit.edu -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads