It is said that 0V indicates a LOW and 3.3V indicates a HIGH. I was wondering if there is a threshold voltage for the HIGH and LOW logic level. Tried searching it, but couldn't find anything.
Thanks in advance.
The specs you want are VIH and VIL. Download the datasheet from TI for more info.
VIH is 2.0v and VIL is 0.8v. The hysteresis minimum is 0.265v.
Related
I am having trouble finding how to read frequencies from audio input. I am trying to listen to very high frequencies (ultrasonic). I've explored several GitHub projects which all were either outdated or malfunctional.
I discovered this guide, but I am having trouble understanding it. https://developer.apple.com/documentation/accelerate/finding_the_component_frequencies_in_a_composite_sine_wave Can anyone provide guidance; has anyone done this before? Thanks
It's worth digging into this piece of sample code: https://developer.apple.com/documentation/accelerate/visualizing_sound_as_an_audio_spectrogram
The sample calculates the Nyquist frequency of the microphone - for example your device might have a maximum frequency of 20KHz. You can look at the values in each frequency domain page of samples and find the maximum value to derive the dominant frequency.
I need to calculate DRAM access latency using given data size to be transfered between DRAM-SRAM
The data is seperated to "load size" and "store size" and "number of iteration of load and store" is given.
I think the features I need to consider are many like first DRAM access latency, transfer one word latency, address load latency etc..
Is there some popular equation to get this by given information?
Thank you in advance.
Your question has many parts, I think I can help better if I knew the ultimate goal? If it's simply to measure access latency:
If you are using an x86 processor maybe the Intel Memory Latency Checker will help
Intel® Memory Latency Checker (Intel® MLC) is a tool used to measure memory latencies and b/w, and how they change with increasing load on the system. It also provides several options for more fine-grained investigation where b/w and latencies from a specific set of cores to caches or memory can be measured as well.
If not x86, I think the Gem5 Simulator has what you are looking for, here is the main page but more specifically, for your needs, I think this config for Gem5 will be the most helpful.
Now regarding a popular equation, the best I could find is this Carnegie Melon paper that goes over my head: https://users.ece.cmu.edu/~omutlu/pub/chargecache_low-latency-dram_hpca16.pdf However, it looks like your main "features" as you put it revolve around cores and memory channels. The equation from the paper:
Storagebits = C ∗MC ∗Entries∗(EntrySizebits +LRUbits)
Is used to create a cache that will ultimately (the goal of ChargeCache) reduce access latency in DRAM. I'm sure this isn't the equation you are looking for but just a piece of the puzzle. The LRUbits relate to the cache this mechanism (in the memory controller, no DRAM modification necessary) creates.
EntrySizebits is determined by this equation EntrySizebits = log2(R)+log2(B)+log2(Ro)+1 and
R, B, and Ro are the number of ranks, banks, and rows in DRAM, respectively
I was surprised to learn highly charged rows (recently accessed) will have a significantly lower access latency.
If this goes over your head as well, maybe this 2007 paper by Ulrich Drepper titled What Every Programmer Should Know About Memory will help you find the elements you need for your equation. I'm still working through this paper myself, and there is some dated references but those depend on what cpu you're working with. Hope this helps, I look forward to being corrected on any of this, as I'm new to the topic.
I saw a linear_quadratic_regulator.h includes infinite horizon fixed point LQR. I am wondering if there is a LQR for finite horizon optimal tracking. I saw some information about tvlqr on the website, but is there any news on it?
Not yet, I'm afraid, but it's coming very soon.
https://github.com/RobotLocomotion/drake/issues/9013
Russ
I was wondering if there was a way that I could detect the exact frequency of a BLE signal with an iphone. I know it will be in the 2.4 GHz range but i would like to know the difference down to the 1 Hz range between the transmitted frequency and the received frequency. The difference would be caused by the doppler effect meaning that the central or the peripheral would have to be moving. Also is there an exact frequency that iphones transmit BLE at or does it depend on the iphone's antenna?
Bluetooth doesn't have one particular frequency it operates on. Via bluetooth.com:
Bluetooth technology operates in the unlicensed industrial, scientific and medical (ISM) band at 2.4 to 2.485 GHz, using a spread spectrum, frequency hopping, full-duplex signal at a nominal rate of 1600 hops/sec.
… adaptive hopping among 79 frequencies at 1 MHz intervals gives a high degree of interference immunity and also allows for more efficient transmission within the spectrum.
So there'll be a wide spread of frequencies in use for even a single connection to a single device. There's hardware on the market like the Ubertooth that can do packet captures and spectrum analysis.
To my knowledge, iOS doesn't offer API to find out this information. OS X does at some level, probably via SPI or an IOBluetooth API, because Apple's Hardware Tools (search for "Bluetooth") offer a way to monitor spectrum usage of Bluetooth Classic devices on OS X.
As to your desire to detect movement via the Doppler effect on the radios, my instincts say that it's going to be very, very difficult to do. I'm not sure what the exact mathematics behind it would look like, but you'll want to examine what the Doppler effect on a transmission at 2.4 GHz would be as a result of low-to-moderate rates of motion. (A higher rate of motion or relative speed, say, over a few tens of miles an hour, will be quickly make Bluetooth the wrong radio technology to use because of its low transmit power.)
A general question: is it possible to retrieve information about how far away e.g. a computer is from a wifi-router. For instance I want to get data on my computer if I'm 10 meters away from my home-wifispot or 2 meters.
Any idea if that is even possible?
Edit: How about bluetooth? Is it possible to get information about how far away bluetooth-connected devices are one from another?
I would recommend a measuring line or just good-old-fashioned guesstimating.
There is no "simple" way to do it (complex ways may involve building "accurate" signal maps ahead of time or trying to fit a better equation which is still subject to anumber of the limitations with the naive rule) and the rule of thumb "1/r^2" is just that -- a general rule of thumb. On the other hand, perhaps there is some existing software that will show you your RSS strength and make the task feel accomplished :-)
You will find useful links if you google for "RSS signal distance". This kind of task seems quite a common topic in academia w.r.t. small wireless devices ("motes") as well and there have been some interesting approaches to this problem such as the fitting of secondary low-frequency acoustic sensors.
You can query the signal strength which is some kind of indication of distance and obstructions and a few other factors all rolled into one measure. With just plain wifi though this isn't possible directly.
Try measuring the response time of the router to pings, with the data rate set to constant to avoid that effecting the response time. Take lots of samples and remove outliers to reduce errors, but you will still have a substantial quantization error. Subtract the latency of the router and computer, divide by 6 then multiply by the speed of light and hopefully you will have the distance to a resolution of a few metres.