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1answer
54 views

How to measure mains frequency safely via GPIO

I would like to measure the mains power (120vac/60hz) to know precisely when the voltage drops to 0, but in a safe manner for the pi - one solution would be to use a high-value resistor bridge that ...
3
votes
2answers
316 views

Problems with Pifm legality

There is a lot of discussion online about whether using Pifm is okay because it is low powered, or whether it is very bad because the square waves cause a lot of interference outside the FM band. ...
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0answers
23 views

What represent the devices that vcgencmd measure_clock can display the frequencies of?

With vcgencmd measure_clock <clock> where <clock> can be one of arm, core, h264, isp, v3d, uart, pwm, emmc, pixel, vec, hdmi, dpi one can display the frequencies of these devices. What ...
2
votes
2answers
169 views

PiFM not transimmiting to some frequencies

I was playing with the PiFm on my Pi and successfully transmitted the sound.wav on a specific frequency. That is 94.5 . But when I am trying to do the same on 89.7 , it does nothing. I changed ...
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vote
2answers
47 views

Why don't I need time:sleep() for talking with a 10MHz chip?

I'm learning to control a MCP4131 digital potentiometer with the RPi. I've successfully used the MCP4131 by sending my data to the SDI pin, and then a HIGH value to the CLK followed by sending a LOW ...
2
votes
1answer
415 views

ADC for ultrasonic frequency recording?

I'm trying to create a prototype using a breadboard that is able to record sounds at the ultrasonic frequency range. I am looking into purchasing this microphone. The problem is that the Raspberry Pi ...
2
votes
1answer
422 views

Set HDMI refresh rate

I would like to set my HDMI refresh rate to 100 MhZ as supported by my TV, however using the code below always set it to 60 MhZ: hdmi_group=1 hdmi_mode=40 Any idea why or suggestions on how to ...
3
votes
1answer
2k views

How does the RF/FM GPIO transmitter hack work?

A while ago, a few guys figured out that they could transmit FM signals using the Raspberry Pi's GPIO ports, and another person realized that he could use the RasPi for controlling his home automation ...
3
votes
1answer
96 views

Power consumption and instruction cycle frequency

I am making a small, mobile device that depends on batteries. It will only require a high CPU frequency occasionally and is at a low frequency the rest of the time. The default frequency is 700MHz. ...
0
votes
1answer
595 views

I²C frequency changeable?

Is the I²C frequency meanwhile changeable? I read a few articles a while ago, that the frequency is not changeable.
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2answers
187 views

How can I change the frequency?

I would like to change the frequency of the RPI, how can I do that, I'm using low level programming. Also how can I get the used memory and free memory?