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I want to have a SPI flash chip that can do 4-bit IO to be accessible as both a memory mapped device to a soft CPU for reading, and as an SPI device for direct access to all the other commands in it, selectable by a register (fl_mem_enable).
This requires multiplexing of inout signals, and i...
Ok, so instead of having two clocks you have one, and explicitly wait for the time it would take the RAM to process?
That works. Tested up to 50MHz with no problems.
So, is that a proper way to do it - keep it all in one clock domain and insert delay states?
Precisely what worked...
Parallel static asynchronous RAM.
The datasheet specifies only the maximum speed (70ns access time), not any particular frequency to be used. AFAIK, it can work down to near-DC.
What sort of wait states do i need?
It's supposed to be clocked at the rate that gives the RAM enough time to respond...
Let's say i have a parallel static RAM that is running at one frequency (8 MHz), and a CPU (in the FPGA) tthat is running at a higher frequency (16MHz).
The CPU asserts a read or write signal, the RAM gets accessed, sets a done flag for one clock, the CPU sees the flag and deassert the request...
Ah, nice.
There was indeed no constraint specified for I2C clock, and so far i haven't been able to reproduce the problem after adding it.
Thanks everyone for suggestions!
Let's say i have a verilog design the size of a small SoC.
It is largely correct, and works nicely in an FPGA on one board.
On another identical board, however, it starts giving out intermittent errors, i.e. the I2C gets garbage sent out every 10 bytes.
But if i do some irrelevant change, like...
You'll need an MP3 shield or a separate player to make the sound, plug it into the microphone port of the SIM900, and control from the Arduino.
Arduino itself is unlikely to be capable of decoding and producing sound on it's own.
Ok, from what i gathered doing that is not quite possible.
Just removing the frequencies would produce ringing, due to the sharp transition invoked - while frequencies inside the bins will be zero, ones between the bins are free to change.
There is something about using window functions to help...
One more question, while it's still related.
I tried to do band-pass filtering by doing FFT of the signal, removing (that is, setting them to (0,0) ) the unwanted frequencies, then doing reverse FFT.
However, that produce chirps in the sound - spikes at the start and end of the segment of...
Aha.
Now that works perfectly and sounds great.
Thanks!
Now it behaves similar to HDSDR - you don't need to track the carrier precisely, just put it close and the sound comes up.
Hm, that seems to be a proper way to do what i was stumbling towards, thanks.
Bad news is, the result is only slightly better.
The sound is still poor.
There is a low-frequency component that sounds like smoothed wind sounds recorded by a very cheap microphone. Highpass does not help much...
Looked through Dan Mills's links. It's either over my head, or not quite related.
All i got from there is how to do low- or high-pass filters in software, which is useful, but does not solve the main problem.
Meanwhile, had a limited success in getting audio.
The input is multiplied by...
Thanks, i'll be looking through them.
Not sure if that is the right thing.
The idea is that there can be several stations within the samples.
One might be at 50KHz, other at 10KHz.
I want to be able to "tune" to one or the other, and get audio.
In more serious SDRs the bandwidth is far greater...
In short, how do you decode AM signal from I/Q samples into sound?
In details, i made an SDR that uses a PC sound card as ADC.
The local oscillator on it is set to 700KHz, there is a radio station at 731KHz.
With existing software i verified that the hardware works - the station is here and i...
Hello.
I'm trying to figure out how to select IGBTs, and am wondering what to believe.
Here are two half-bridge modules:
CM400DU-12F, https://www.digikey.com/product-search/en?vendor=0&keywords=cm400du-12f
APTGT300A60G...
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