gloomyandy wrote:Aswin quick question. What voltage are the clock and data lines at if you have the IMU powered up, with the pull-ups connected but with neither the NXT or the bus pirate connected to them?
mattallen37 wrote:I looked at the blinkM datasheet, and it looks like it is supposed to be 5v, not 3.3v.
mattallen37 wrote:Anyhow, I didn't see VIL for it, but if you are using 47k up to 3.3v for the blinkM, and it works, VIL must be at least 0.3v (vs. 0.1 for the IMU)
nxtreme wrote:IIf your in need of an oscilloscope, you might try a software 'scope. While they aren't exactly fast or terribly accurate, they might work for slower baud rates. Check out this post on LMR, it mentions software for both Linux and Windows. You'll need to put together a bit of additional hardware to protect your sound card but it shouldn't be too hard .
Well, I am not really doing that. If it works using 47k pullups to 3.3v, then I use the voltage divider equation to figure out the lowest voltage that it is getting, and since it functions at that voltage, I can assume that VIL is at least that voltage. In this case, using a 47k pullup to 3.3v, and having a 4k7 resistor to LOW, the voltage between them (the IO line) is at 0.33 volts. since it works at that, it is obvious that VIL must be >= 0.33 volts.aswin0 wrote:It seems that you calculate the VIL from the pull up value. How do you do that?
gloomyandy wrote:Hmm 0.97 sounds a little low for a line that should really be an input in that state. I suspect that the NXT may end up seeing that as logic level 0 and may refuse to even begin to try and drive it with i2c. How do those voltages compare to having the blinkM in the circuit (on its own with no NXT connected but running from 3.3v)?
I know, but when the NXT pulls the pin to LOW, it is as if the 4k7 resistor was a pulldown resistor to the IO line at the port.gloomyandy wrote:Matt there is no 4.7K resistor to LOW? There is a current limiting 4.7K resistor in the input line and a 1M resistor to ground then a couple of clamp diodes:...
Users browsing this forum: No registered users and 2 guests