Electronics > Electronics
pull up resistors?
JesseWelling:
Here is my issue. I've got a Maxbotix Sonar Sensor. It outputs serial inverted which is to say 0v is logic 1, and 5v is logic 0.
My atmell AVR128 only has a regular UART (5v logic 1, 0v logic 0). I do have some 74LS05 logic inverters but I think I need a pullup resistor so that the line stays high (or low I havn't figured it out yet) when not in use (eg not being driven by the MaxBotix Sonar Sensor). I don't need to send any thing to the the Sonar Sensor...just recieve the acurate ranging data on the serial line. I Can't use the PWM of the Sonar because no more timers are available for me to use on the AVR and I don't want to deal with use the noisy analog because of the time lag in the readings.
Any one deal with this kind of thing before?
Admin:
ive used sonar without knowing what pull-up resisters were . . . so you probably dont need them. :P
the sonar pulse line will never be random - the circuitry goes high only when receiving a pulse, otherwise it is low.
any possibility you could use a single interrupt for multiple components? ive used 3 sonar on a single interrupt . . . an interrupt could ignore its normal function if it is called when your main() is in the read sonar loop . . .
JesseWelling:
I think you misunderstood me. But I have it figured out so no worries :P
Militoy:
Glad you got it figured out, Jesse. The inverter chip you're using is a low-power schottky type, so as long as your sensor is pulling each 74LS05 gate below 0.8V, you'll get a solid "1" out, and if it's driving to above 2.0V, you should get a good "0".
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