On Tuesday 26 June 2007 03:15:26 am [EMAIL PROTECTED] wrote: > Hi i use tmote and tinyos 1.1 ; i must use ADC to sample a voltage on > Capacitor but i have a problem. In fact i use ADC3 and GND(of ADC) but this > pin result short-circuit when tmote is on. This is a big problem for me > because the capacitor discharge and i can't mesaure the really value. How > can i resolve my problem??
Not sure, but I can see a few ways this could be happening. 1. The IO pins of the msp430 are set at PUC (power up clear) to digital IO inputs. In this state, the pins leak almost no current *unless* the voltage they see is not very close to Vcc or Vss (uC GND). If the msp430 resets while or after the cap is charged, the cap may be applying a voltage to the pin that could cause it to leak 100+ uA, which could be at least partially draining the cap before software takes over and sets the ADC3 pin into its peripheral ADC mode. 2. The software is somewhere setting the ADC3 pin to a digital output with a level of 0. This will cause the pin to sink current from the capacitor and drain it. This situation could cause the msp430 to be damaged if the capacitor's charge into the pin could exceed the pin's maximum current handling capability. 3. The capacitor's energy storage is so small that even the tiny amounts leaked at ADC3 or drawn during sampling is adversely affecting the charge. Steve _______________________________________________ Tinyos-help mailing list Tinyos-help@Millennium.Berkeley.EDU https://mail.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
