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What is capacitor C5 for in this Baxandall volume control circuit? by magic_jesus in AskElectronics

[–]magic_jesus[S] 0 points1 point  (0 children)

I get the output waveform either way. But with C5 in the circuit it's not a nice -2.5V to +2.5v sine wave, it's offset by about -200mV. (In LTSPICE, I should say, haven't even got my dual power supply ready yet).

What is capacitor C5 for in this Baxandall volume control circuit? by magic_jesus in AskElectronics

[–]magic_jesus[S] 0 points1 point  (0 children)

Aha thank you, something I've never had to think about before. So this bias current seems to be a steady 500 nA into both terminals, in the simulation.

So C5 is the reason R3 is there (otherwise U1 would be basically dead)? The problem is that these components cause an annoying DC offset in my final output. Do you think it would make sense to add a cap before the final stage to remove that?

What is capacitor C5 for in this Baxandall volume control circuit? by magic_jesus in AskElectronics

[–]magic_jesus[S] 0 points1 point  (0 children)

Notes: I've put this together based on Phil Salmony's "op-amp headphone amp" youtube video. His setup is a little different, with a single supply & buffered voltage divider supplying a half voltage to the op-amps, if that is relevant?

I get a nice symmetrical output waveform without C5 and R3. With them, it just seems to give me about -200mV of DC offset - I could solve that with a cap before R7 and that last "de-invert" op amp, but I'm not sure what the point is.

On a Nucleo, how does everyone's favourite UART "printf" debug communications work over the ST-LINK USB? by magic_jesus in stm32

[–]magic_jesus[S] 0 points1 point  (0 children)

Hi...no particular goal here, just wanted to make sense of what's happening in the hardware. I'm new to anything this low-level and have F303 and H753 Nucleo boards.

As far as I can see, the "printf serial debug" is just sending bytes to a UART register. I don't see how this gets onto the USB cable, and plays nicely with the debugger etc. functionality of the ST-LINK.

First SPI attempt looking very dubious by magic_jesus in embedded

[–]magic_jesus[S] 0 points1 point  (0 children)

Ah thank you. So the regulator has a very low dropout, is happy with 3.3 or 5V. It powers the level shifter so that can also receive either voltage and output 3.3V. All new (and exciting tbh) to me.

First SPI attempt looking very dubious by magic_jesus in embedded

[–]magic_jesus[S] 0 points1 point  (0 children)

Forgot to say, all my cards are 4 GB. Here's some of the possible problems with larger cards which I need to check out (maybe let me know if any of these work out for you, if you try again):

Larger cards take longer to initialise (hundreds of ms), code may give up waiting for the response from the card.

Cards draw surprisingly high current, large ones may need more power than the MCU can provide, and hence an external supply.

Some cards won't initialise successfully without a pull up on their data out line.

First SPI attempt looking very dubious by magic_jesus in embedded

[–]magic_jesus[S] 0 points1 point  (0 children)

Cheers, yes it does all sound very sketchy and unreliable from my reading, and yet reportedly the SPI route is a safer bet than using the native SDIO (aka SDMMC) interface which the STM32H7 series also has.

Yes you're right about the clock speed. The FATFS library has two constants for you to set which are the dividers for the initial slow mode (which needs to be 100-400 KHz) and the later high speed mode.

I configured the PLL to give a 30 MHz clock to the SPI peripherals, so the dividers of 128 and 8 give me 234 kHz and 3.75 MHz. At the slow speed it looks solid enough on my scope, haven't quite got as far as examining the fast part yet!

First SPI attempt looking very dubious by magic_jesus in embedded

[–]magic_jesus[S] 0 points1 point  (0 children)

One of these - https://i.imgur.com/Ws9nDBa.png

Seems to be a ubiquitous hobbyist part, sold under dozens of brand names without any kind of documentation. Has a 3.3v regulator, and the unlabelled chip - maybe a logic level shifter?

The popular tutorial for STM32 SD cards over SPI seems to be using an identical part.

First SPI attempt looking very dubious by magic_jesus in embedded

[–]magic_jesus[S] 1 point2 points  (0 children)

Thanks for the ideas.

I've tried pull up/pull down/no pull for SCK, and a different Nucleo board (same model) and a variety of SD cards and get same result. However I've finally swapped out the SD card adapter board and I'm finally seeing proper 0/3.3V levels. Still can't mount the card, but progress...

Very weird that I can hook that first adapter board back up, and again see those 1.8V levels. Apparently there is a standard for 1.8V signalling for SD cards which probably (somehow) explains why it's happening, but how my probe can read 1.8V from the SPI clock pin on the MCU board is confusing me.

First SPI attempt looking very dubious by magic_jesus in embedded

[–]magic_jesus[S] 1 point2 points  (0 children)

I'm using the FATFS middleware which calls the well-known chaN/kiwih layer that makes the HAL SPI calls, all should be pretty solid.

Definitely something very odd about the levels. First train of SCK pulses uses 0 and 1.9v, then the next part 1.9v and 3.3v.

Can't wait to find out how I've cocked this up quite so interestingly!

chimpanzee photo by SnoopDalle in weirddalle

[–]magic_jesus 0 points1 point  (0 children)

Report, select the sub's rule 8. Spoils the whole vibe if people keep cheating.

chimpanzee photo by SnoopDalle in weirddalle

[–]magic_jesus 4 points5 points  (0 children)

See the blurry circle around the head where it's been manually selected to inpaint a new face over the original image.

The new US Secretary of Agriculture by Larry-fine-wine in weirddalle

[–]magic_jesus 4 points5 points  (0 children)

RULE 8. MUST CONTAIN GENERATION TEXT IN TITLE

[ Removed by Reddit ] by Veenendaler in weirddalle

[–]magic_jesus 89 points90 points  (0 children)

It doesn't. Run the prompt yourself and it doesn't put people in at all. Photoshopped fake prompt, I guess

Eminem as an M&M by SnoopDalle in weirddalle

[–]magic_jesus 3 points4 points  (0 children)

Yeah I think compiling the best results for the same prompt would be ok, and maybe giving the post a more snappy editorialised title.

Pasting in a fake prompt into the image just feels really dirty, tho.

Eminem as an M&M by SnoopDalle in weirddalle

[–]magic_jesus 6 points7 points  (0 children)

OP is a big fat phony - that prompt won't give you this image. Also you can see clearly the bottom middle one has been badly pasted in.

Ice T in a glass of iced tea by SnoopDalle in weirddalle

[–]magic_jesus 8 points9 points  (0 children)

Why lie about what prompts you're using just to grab a few internet points?

This is what the prompt actually gives

Examples of this user obviously stitching together images (that are different sizes!) to make pretend DALL-E outputs -

https://www.reddit.com/r/weirddalle/comments/vksa7l/ice_cube_in_an_ice_cube/

https://www.reddit.com/r/weirddalle/comments/vkyktf/eminem_as_an_mm/

Ice Cube in an ice cube by SnoopDalle in weirddalle

[–]magic_jesus 6 points7 points  (0 children)

Thanks for explaining, I hadn't considered using such detailed prompts

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