I'm trying to use a Raspberry Pi Pico to measure an incoming PWM signal duty cycle and use the value to drive an I2C digital potentiometer. I'd like to use micropython as I know some of this already. The I2C output I have working with no problems. However I can't find where to start with the PWM measurement.
The RP2040 datasheet suggests it is possible to use the PWM slices to measure duty cycle, but the micropython PWM commands don't seem to utilise this (https://docs.micropython.org/en/latest/library/machine.PWM.html)
I can't see how to access the PWM slices directly in micropython
The "rp2" micropython — functionality specific to the RP2040 does not reference PWM as far as I can see. (https://docs.micropython.org/en/latest/library/rp2.html)
There are ways to measure PWM by using some coding but I would like to do it using the hardware as this frees up the processor for other tasks and it should also be more accurate I believe.
Perhaps I am just missing some documentation - any pointers much appreciated.
Chris
EDIT: I have found a useful module which covers a large part of this query:
https://github.com/phoreglad/pico-MP-modules/tree/main/PWMCounter
Is it possible to wake up XBee end device with input (high) from sensor? According to documentation:
"When the device asserts (high) Sleep_RQ, it finishes any transmit or
receive operations and enters a low power state."
But in my case i need inverse logic. Sensor (e.g motion sensor) setting it's control pin to high when motion detected.
It is not possible to invert the logic of the XBee itself. But of course you can connect an inverter (NOT gate) to the pin. This can be as simple as a transistor and two resistors, but if you want to save energy, have a look at the CMOS inverter type or special low power components.
How can I receive a time signal with an unmodified RTL-SDR USB TV Dongle here in Europe?
RTL-SDR Dongles are able to receive the frequency range 52-2200MHz.
Here in Europe, radio-controlled clocks receive DCF-77, a time signal broadcast on 77KHz, but as 77KHz is a bit lower than 52MHz, that's out.
The GPS L2 signal is at 1575.42 MHz, so that's within the dongle's range, but the signal is way too weak to be received with the TV antenna. An active GPS antenna is needed, and for providing the antenna with the power, I'd need to make some modifications to the electronics which I don't really want to do.
In the old age of analog TV broadcasting, we had Teletext / Videotext here in Germany, which contained a time signal, but these times are long gone.
ADS-B reception with a dongle works like a charm, but unfortunately they did not put in time or date bits into the data packets.
So: Does anybody have any idea where in the spectrum that can be received by an unmodified RTL-SDR dongle there is a time signal that could be easily decoded?
I'm well aware that getting time over the network via NTP, or via a GPS modem via NMEA 0183 would be way easier, but I'm curious and just want to play around with that dongle a bit. Precision is not important. +/- 2 seconds is fine. And I'd like to do it the SDR-way, so using the dongle in the originally intended way (as a DVB-T receiver using the original software) defeats the purpose (i.e. learning and DIY)
The GPS L2 signal is at 1575.42 MHz, so that's within the dongle's range, but the signal is way too weak to be received with the TV antenna. An active GPS antenna is needed, and for providing the antenna with the power, I'd need to make some modifications to the electronics which I don't really want to do.
Well, first of all, GPS is really weak, but it still works under the noise floor; that's something important to realize – I've seen it more than one time that people are worried because they can't see GPS on a PSD display. You won't; you'll need signal processing to recover it from all the noise.
The modifications aren't all that complicated; basically, you need a capacitor to let through the AC component to the RTL dongle, and a voltage source to feed the active antenna; the required component is usually called a bias-T.
Nevertheless, an active antenna will be necessary – your RTL dongle probably won't have a Noise Figure low enough to receive GPS signals on its own.
In the old age of analog TV broadcasting, we had Teletext / Videotext here in Germany, which contained a time signal, but these times are long gone.
True; haven't looked at local FM stations, but RDS might be the way to go – it can contain a clock/time signal; the German Wikipedia claims that mainly publicly owned stations transmit that information field.
Have a look at gr-rds; it's a GNU Radio implementation of the Radio Data System. If you don't have a working GNU Radio installation (yet), you might try out the GNU Radio LiveSDR Image, which contains a ready-to-use gr-rds.
I'm trying to do an experiment to see how different on-chip temperatures affect the frequency of ring oscillator. I know that as the temperature increases, the frequency of the ring oscillator also decreases. But I don't know how much it will decrease for every 1 degree Celsius increase. And that's why I want to do the experiment. I'm planning to implement the ring oscillator in a Xilinx Virtex-5 FPGA board (ML501, ML506, or ML510) because those are the only boards that I have. Does anyone know how I can get an accurate reading of the on-chip temperature in Virtex-5?
You're in luck -the V5 was the first generation to support the system monitor block.
You can use chipscope to read back the temperature live, or else instantiate the sysmon and read the temperature out from register 0.
i have a GPS NTP Time server synchronizing my PC.
HOW am i able to compare 1PPS of the GPS receiver with clock pulse of my PC to see how much accurately it is synced to the GPS time?(with an oscilloscope maybe!)
I've designed experiments of this sort before. In my case, I wrote a device driver that would -- inside the kernel -- watch the PC's clock in a tight loop waiting for it to roll over to a new second. As soon as it did, I would raise one of the pins high on the PC parallel port. Then I attached that pin of the parallel port and the PPS signal output of the GPS receiver to an oscilloscope and had it measure the time difference between the two pulses.