I am trying to get data samples from a sensor using a ADS1256 library with a Raspberry Pi High-Precision AD/DA Expansion Board on my RaspberryPi 2B
Now as mentioned in their code and datasheet it can take around 30,000 samples per second, but when I am running it, it was taking around 15 samples per second. After some modifications in code, it is taking around 470 samples per second.
I need atleast 1000-1500 samples per second.
Here again is the link to the ADS1256 code.
I tried to use this at a higher rate of speed. If you are waiting for DRDY pin to go low for on the order of milliseconds it isn't going to work. I had no luck in modifying the software. I tried to use this http://abyz.me.uk/lg/lgpio.html#lguSleep but I never could get the interrupt to activate on the change of DRDY. It seems that the person who wrote the sample program for the ADS1256 could not either. I looked at the sample program for the mpc3202. http://abyz.me.uk/lg/lgpio.html#lguSleep He does similar things; He sleeps for .2s between samples. That won't work for his sample rate. One problem is that the raspberry pi has no real-time clock. I tried some unix time routines and got back 0 as a result.
Related
I am using a G0 with one ADC and 8 channels. Works fine. I use 4 channels. One is temperature that is measured constantly and I am interested in the value every 60s. Another one is almost the opposite: it is measuring sound waves for a couple a minutes per day and I need those samples at 10kHz.
I solved this by letting all 4 channels sample at 10kHz and have the four readings moved to memory by DMA (array of length 4 with 1 measurement each). Every 60s I take the temperature and when I need the audio, I retrieve the audio values.
If I had two ADC's, I would start the temperature ADC reading for 1 conversion every 60s. Non-stop. And I would only start the audio ADC for the the couple of minutes a day that it is needed. But with the one ADC solution, it seems simple to let all conversions run at this high speed continuously and that raised my question: Is there any true downside in having 40.000 conversions per second, 24 hours per day? If not, the code is simple. I just have the most recent values in memory all the time. But maybe I ruin the chip? I use too much energy I know. But there is plenty of it in this case.
You aren't going to "wear it out" by running it when you don't need to.
The main problems are wasting power and RAM.
If you have enough of these, then the lesser problems are:
The wasted power will become heat, this may upset your temperature measurements (this is a very small amount though).
Having the DMA running will increase your interrupt latency and maybe also slow down the processor slightly, if it encounters bus contention (this only matters if you are close to capacity in these regards).
Having it running all the time may also have the advantage of more stable readings, not being perturbed turning things on and off.
I am using a RSPI Zero W to record videos using motion detection. I have read others doing this easily with frame rates of 5 per second and above. I am only trying to get 2 frames per second.
Everything works fine, except the videos recorded do not keep up with real time. I still get 2 frames per second, but many of the frames are duplicates.
It seems that the PI0W can not keep up with it, but the CPU usage never gets much higher than 50%. Using a Class 10 SD card so I do not think it is a disk I/O problem.
I originally did this on a PI2B with no problems in 720p. I tried reducing the resolution to 640x480 and get the same result.
Any suggestions?
Setup:
Raspberry Pi Zero W
Raspbian 9.4 stretch
Apache/2.4.25 (Raspbian)
PHP 7.0.27-0+deb9u1
Samba Version 4.5.12-Debian
Motion 4.0 (installed via apt-get)
motion.conf
https://pastebin.com/Mr438ned
Example Video: Watch the timestamp. It should be updating every second
I have a project that consisted of transmitting data wirelessly from 15 tractors to a station, the maximum distance between tractor and station is 13 miles. I used a raspberry pi 3 to collect data from tractors. with some research I found that there is no wifi or GSM coverage so the only solution is to use RF communication using VHF. so is that possible with raspberry pi or I must add a modem? if yes, what is the criterion for choosing a modem? and please if you have any other information tell me?
and thank you for your time.
I had a similar issue but possibly a little more complex. I needed to cover a maximum distance of 22 kilometres and I wanted to monitor over 100 resources ranging from breeding stock to fences and gates etc. I too had no GSM access plus no direct line of sight access as the area is hilly and the breeders like the deep valleys. The solution I used was to make my own radio network using cheap radio repeaters. Everything was battery operated and was driven by the receivers powering up the transmitters. This means that the units consume only 40 micro amps on standby and when the transmitters transmit, in my case they consume around 100 to 200 milliamps.
In the house I have a little program that transmits a poll to the receivers every so often and waits for the units to reply. This gives me a big advantage because I can, via the repeater trail (as each repeater, the signal goes through, adds its code to the returning message) actually determine were my stock are.
Now for the big issue, how long do the batteries last? Well each unit has a 18650 battery. For the fence and gate controls this is charged by a small 5 volt solar panel and after 2 years running time I have not changed any of them. For the cattle units the length of time between charges depends solely on how often you poll the units (note each unit has its own code) with one exception (a bull who wants to roam and is a real escape artist) I only poll them once or twice a day and I swap the battery every two weeks.
The frequency I use is 433Mhz and the radio transmitters and receivers are very cheap ( less then 10 cents a pair if you by them in Australia) with a very small Attiny (I think) arduino per unit (around 30 cents each) and a length on wire (34.6cm long as an aerial) for the cattle and 69.2cm for the repeaters. Note these calculations are based on the frequency used i.e. 433Mhz.
As I had to install lots of the repeaters I contacted an organisation in China (sorry they no longer exist) and they created a tiny waterproof and rugged capsule that contained everything, while also improving on the design (range wise while reducing power) at a cost of $220 for 100 units not including batterys. I bought one lot as a test and now between myself and my neighbours we bought another 2000 units for only $2750.
In my case this was paid for in less then three months when during calving season I knew exactly were they were calving and was on site to assist. The first time I used it we saved a mother who was having a real issue.
To end this long message I am not an expert but I had an idea and hired people who were and the repeater approach certainly works over long distances and large areas (42 square kilometres).
Following on from the comments above, I'm not sure where you are located but spectrum around the 400mhz range is licensed in many countries so it would be worth checking exactly what you can use.
If this is your target then this is UHF rather than VHF so if you search for 'Raspberry PI UHF shield' or 'Raspberry PI UHF module' you will find some examples of cheap hardware you can add to your raspberry pi to support communication over these frequencies. Most of the results should include some software examples also.
There are also articles on using the pins on the PI to transmit directly by modulating the voltage them - this is almost certainly going to interfere with other communications so I doubt it would meet your needs.
I have been following a tutorial that enables you to play around with the TXPOWER parameter of your wifi card / wifi adapter:
http://null-byte.wonderhowto.com/how-to/set-your-wi-fi-cards-tx-power-higher-than-30-dbm-0149606/
You can easily boost up your wifi range when increasing the TXPOWER.
Now, most people want to improve their wifi signal strength of their home router, right. But in my case, I would like my home router (which runs on a raspberry pi) to have a relative small wifi signal radius (say, a radius of 2 meters), so that you actually need to physically look for the pi home router when trying to connect to it.
I have learned that this tutorial does not do a thing with the wifi link quality and/or the wifi signal level and thus does not influence the wifi radius of my pi home router.
link quality & signal level
Do you guys have any ideas/thoughts about how to decrease link quality and/or wifi signal level (e.g Link Quality = 12/70 and Signal level =-10dBm) ? Is this even possible ?
I am using a Tp-Link TL-WN722N IEEE 802.11n USB - Wi-Fi Adapter.
WIRELESS LITE N ADAPTER 150M USB HIGH GAIN 1DETACHABLE ANTENNA WL-AP.
150 Mbps - External
First, I recommend reviewing this section from your link:
QUICK DECIBEL UNDERSTANDING:
Every 10 decibels is a 10X increase in power starting from 1 dBm equal
to 1mW... 10 dBm equals 10 mW, 20 dBm equals 100 mW, 30 dBm equals
1000 mW, and so on. Every 3 decibels is approximately double that of
the prior power, so 30 dBm is 1000 mW, if we add 3 dBm, then we can
double the power such that 33 dBm is about equal to 2000 mW.
It appears to me that you are able to modify the transmit power of your adapter as the tutorial states. Are you saying this is not working? If you set your transmit power to something extremely low (-30dBm, for example) you would effectively be turning off the transmitter. Keep increasing that value until you get your desired coverage radius.
If the transmit power parameter is not functioning as per the tutorial, then there are other means to achieve reduced coverage. The model you specified has a detachable antenna....so detach it. This would definitely reduce your coverage. However, if it reduces coverage too much, you could simply add an inline attenuator. Fortunately, your antenna uses an SMA connector which is very common. You can find many SMA attenuators on ebay with different attenuation values. Experiment with different values until you get the desired coverage.
And if that doesn't work, just wrap a bunch of aluminum foil around the thing lol.
Looking for some help to be honest, This is not my area of knoladge atall.
Ive read around the question of powering my Pi with a battery, now I nabbed one of these guys for my phone
http://www.amazon.co.uk/13000mAh-Portable-External-Technology-Motorola-Black/dp/B00BQ5KHJW/ref=sr_1_cc_1?s=aps&ie=UTF8&qid=1420826597&sr=1-1-catcorr&keywords=anker+astro+e4
Incase the link dies in the future;
Item model number: AK-79AN13K2-BA
Anker® 2nd Gen Astro E4 13000mAh 2-Port (3A Output) Fast
Max 3A Out
5V Out
Now, from what i've read there have been mixed notes of, don't use batterys, only use this battery, don't do this, don't exeed this magical number ( which was differant each time ). so any help would be grately needed. If i was to power my pi via this thing. im I going to get a poof of smoke and need to replace the poor pi :(
A raspberry Pi is powered via USB, which means that it simply takes the 5V supplied via USB to run. As long as your current source is stable (ie. it doesn't change when you draw current from it), no device will care whether it is a battery or a switching power supply. Now, a bare raspberry Pi B uses less than 2W of power, 2W/5V = 0.4A = 400mA, so if that battery pack lives up to its specification, you are going to be fine. The device is spec'ed to provide 13000mAh, so at a constant current of 400mA, this would last you more than 32 hours.
Now, most people attach something to the raspberry, and that something will also draw power, but just add that power to the calculations above, to see if it's going to work out.