Recent Posts

1

Beginners / Re: Quickly Triggering Sensors - need an oscilloscope? what specs? (AU)

« Last post by nate_syd on Today at 09:22:29 pm »

You need Pattern Generator. https://en.wikipedia.org/wiki/Digital_pattern_generator
https://digilent.com/reference/test-and-measurement/guides/waveforms-pattern-generator
Digilent Analog Discovery 3 -  https://digilent.com/reference/test-and-measurement/analog-discovery-3/start

This was REALLY helpful - much appreciated!
Might grab the Disco2, significantly cheaper & good enough for my use case

2

Microcontrollers / STM32F407 - CMSIS DSP - IFFT not working with audio input/output

« Last post by lukegalea16 on Today at 09:22:20 pm »

I'm currently using the stm32f407g-disc1 and reading an audio input through PMOD I2S2. I've carried out some examples and the hardware is working fine (writing data from the rx to the tx buffer) such as the code below.

Code: [Select]

for (int i=0; i<BUFFER_LENGTH*4; i=i+4) {
txBuf[i] = rxBuf[i];
txBuf[i+1] = rxBuf[i+1];
txBuf[i+2] = 0;
txBuf[i+3] = 0;
}

I now wish to perform the FFT on this incoming buffer, manipulate it (my first aim is to implement a pitch shifting algorithm) and perform the IFFT again. Thus I've tried the following:

Code: [Select]

for (int i=0; i<BUFFER_LENGTH*4; i=i+4) {
fft_in_buf[fft_in_ptr] = (float) ((int) (rxBuf[i]<<16)|rxBuf[i+1]);
fft_in_ptr++;
}

arm_rfft_fast_f32(&fft_handler, fft_in_buf, fft_out_buf, 0);
arm_rfft_fast_f32(&fft_handler, fft_out_buf, fft_in_buf, 1);

fft_in_ptr = 0;

for (int i=0; i<BUFFER_LENGTH*4; i=i+4) {
        txBuf[i] = (fft_in_buf[fft_in_ptr] >> 16) & 0xFF; // MSB
        txBuf[i + 1] = fft_in_buf[fft_in_ptr] & 0xFF;     // LSB
        txBuf[i + 2] = 0;
        txBuf[i + 3] = 0;

        fft_in_ptr++;
}

In the main initialization I'm also carrying out

Code: [Select]

arm_rfft_fast_init_f32(&fft_handler, BUFFER_LENGTH);

My issue is that I get a very very low output (barely audible) with the above code. I might have a scaling issue as I found in similar issues but I still can't get it to work by scaling fft_in_buf[fft_in_ptr].

3

Beginners / Re: LiPo battery charging problem

« Last post by nate_syd on Today at 09:21:12 pm »

If you want to know more about battery longevity - youtube some Jeff Dahn videos, he goes into depth on why you only 80% charge etc.

4

Projects, Designs, and Technical Stuff / Re: (Yet Another) DIY Multislope ADC

« Last post by Kleinstein on Today at 09:19:45 pm »

To make use of the extra resolution gained from the rundown part one would need additional gain for the residue ADC. Without extra gain there is not much gained.

The comparator noise  should not be an issue - it only increases the range that the residue ADC has to cover a little.
For the aux ADC it is often more the amplifier than the actual ADC noise. With less resolution needed from the aux ADC it would be less than before.
Including the rundown part makes the aux ADC less critical (get some 5 bits from the rundown instead) and even the internal ADC may than be good enough.

Wanting the 12 MHz for an easy code download is a good point.

5

Beginners / Re: Fast PWM IC

« Last post by coppice on Today at 09:19:44 pm »

If you really want a PWM channel running at 100MHz with any kind of reasonable resolution for the pulse width trying looking at things like the TI C2000 MCUs. They have a pulse width resolution far beyond their clock rate, using calibrated delays.

6

Test Equipment / Re: JunTek PSG9080 Programmable Signal Generator (80 MHz - 300 MSa/s - 14-bit)

« Last post by eTobey on Today at 09:12:27 pm »

How does this look to you?

7

Computers / Re: Format a 256GB pendrive with FAT32 using a windows 10 pc

« Last post by DavidAlfa on Today at 09:10:57 pm »

Yeah, try with this tool:
https://www.bleepingcomputer.com/download/hp-usb-disk-storage-format-tool/

8

Repair / Re: Desoldering advice

« Last post by fmashockie on Today at 09:10:34 pm »

Glad to hear it! And that you got the scooter working!

It may not have been the original cause you were thinking, but you got to it eventually.  Plus you learned a new skill along the way!

9

FPGA / Re: Analog video output with FPGA ?

« Last post by SiliconWizard on Today at 09:09:26 pm »

Well, are you sure you need 24-bit RGB to drive an old CRT TV anyway? I am not.

This is a good question. My idea was to start with 24bits on the prototype, then lower the bit-depth via software to see if I can reduce the cost and size (and soldering time/difficulty since the project might be open sourced if it works, and should be hobbyist friendly)

16bits RGB might be good enough, but at my current stage (just learning) prototyping with 24 bits won't cost more than prototyping with 16. Unless I go for and exernal DAC and can find a fast enough 6 bit one for cheaper (and with longer expected availability) than the dedicated 24bit video DACs.

Well yes, going for a lower bit depth would just be a benefit if you used R-2R ladders. Something that could still be considered if cost is really a concern.

Since you mentioned using MCUs (I think?), note that generating RGB video at these resolutions would be plenty feasible with just a RP2040 and its PIO. But given its limited number of GPIOs, you'd probably have to limit the bit depth to something lower.

10

General Technical Chat / Re: Is LinkedIn worth keeping?

« Last post by tom66 on Today at 09:08:14 pm »

I must be living in a backwater. Why is contacting you at work - by a headhunter - dumb? How else are they supposed to contact you@your_work since I'm pretty sure you wouldn't splash your private phone number and email all over the interwebs (and if you did, probably not link them to your CV). Worst case, surely, is they get blocked by your company but there's a chance you may follow up, which is all they're after in the end.

Well, he didn't leave a phone number, so was expecting an email response, from my work email, about a competing job?

No, I am not going to do that.  Unprofessional to use your employer's computer systems to search for other jobs (and potentially a breach of contract) for one.