DIY: norns shield

alley_cam · 2020-10-12T22:45:35.162Z

Ahh bummer on the wrong part!

Double check everything else on your order for the prepopulated boards, but those two are the easiest components to work on given the size.

Judging by your codec soldering, you got the skills to switch out the wrong components to the two caps no problem.

Easy breezy, best lesson to learn is a cheap one we’ve all been there for sure

corpusjonsey · 2020-10-12T22:49:08.701Z

infovore:

I’ve not met a cheap multimeter without a continuity mode

There she is.

DMM2357×3894 1.01 MB

chrisbob12 · 2020-10-12T23:36:15.328Z

Shout out for advice here. I built up my norns shield a month ago, and it was working fine. I even did an arcologies workshop with it. Just now, I’d been playing with it. Put it to sleep, unplugged it and came back, plugged it in and it wasn’t working any more. Raspi’s red light came on, and only on the first attempt at powering on, I jiggled encoders and jabbed knobs and got a bit of defective opening animation. For all further attempts, it just sits there with the red power LED on.

This is with a Raspi 3b+ and a correctly rated Raspi PSU. All mounted in the shield kit case, so unlikely to have received an inadvertent short.

The SD card shows credible file structures and I have reflashed it a couple of times, but still the same result.

alley_cam · 2020-10-12T23:55:33.245Z

Getting the startup tone at all?

If you have another SD card lying around to flash that would be a place to start.

I’ve had some issues with cheap cards and only use the Sandisk Ultra now. Flashing is much quicker too.

Pictures of the board would help!

infovore · 2020-10-13T06:54:23.424Z

Blimey. I stand corrected. (The diode test and continuity mode aren’t the same thing.)

eigen · 2020-10-13T09:04:54.589Z

Hello,

I have an issue with very low input level on my norns shield (bought secondhand).

I guess i’ve found the culprit but would like to validate with you before heating up the soldering iron.

norns_shield_input647×612 279 KB

I have R8 and R10 with code 188 which seems to correspond to 1.8G ohm.

If I follow the schematic, those should be 1.5k ohm, that gives code 152.

My shield is revision 191106.

Does my analysis seem correct?

EDIT: I’ve also tried measuring C10/C12 and C11/C13 on board and get ~= 7.3uF for each of them. But my guess is that they shouldn’t be measured on board (plus my multimeter is a no fluke, I just discovered is has a capacitance mode as it isn’t even labeled on its body).

ramphands · 2020-10-13T10:57:12.598Z

Your resistor code is 18B - 1.5k 1% tolerance, in other words correct.

kiloohm.info

Calculate EIA-96 SMD resistor: 18B

eigen · 2020-10-13T11:19:04.263Z

ramphands:

Your resistor code is 18B - 1.5k 1% tolerance, in other words correct.

Sheesh, you’re right.

The problem must lie somewhere else. Guess I’ll have to borrow a scope.

If everyone has a suggestion, I’ll be gratefull.

I don’t think the audio codec chip could be the culprit, they are generally tested during production.

I also booted on a freshly flashed SD card and have the same issue, so that can’t come from the software side.

coolcat · 2020-10-13T12:04:41.559Z

Agree, should not be a problem once I get the parts

Thank you all for your help and support. You are awesome!

chrisbob12 · 2020-10-13T17:36:18.438Z

No startup tone, no green LED. The SD card is a SanDisk per recommendations on this forum. I have flashed to a Samsung SD (known good to run a Pine 64) - still nothing.

I have disassembled, and photos to follow.

It would be useful to know if the Pi needs the shield to boot - @tehn is that the case?

zebra · 2020-10-13T21:05:58.120Z

chrisbob12:

It would be useful to know if the Pi needs the shield to boot

it doesn’t need the shield to boot, only to successfully launch jackd and etc

chrisbob12 · 2020-10-13T23:56:50.254Z

Thanks @zebra that suggests to me that I need to swap out the Pi next.

chrisbob12 · 2020-10-17T18:53:44.030Z

OK, I received a new Pi today, plumbed it in and it all works again. Phew!

I may have fried the original Pi by sharing the mains power distribution with something noisy, although everything else seems to be unaffected

xmacex · 2020-10-19T08:29:41.460Z

In good contrarian fashion, since I see questions/requests/hopes/desires that the norns shield would work with RaspberryPi 4 in addition to the 3 it is designed for, I have started to wonder if the norns shield would work with the older RaspberryPi 2 instead?

Speaking for myself, I see an lot of reasons to interested this. Has anyone tried it or are there reasons to think it wouldn’t work, or arguments to abandon thoughts in this direction?

tomw · 2020-10-19T09:01:06.627Z

The shield will work with a Pi 2 but…

I’ve got a shield on a Pi 3 and another one I put on a Pi 2 I had that was doing nothing. Everything seems to work fine on the Pi 2 but its worth noting that all of the scripts are written for the Pi 3 so you could have issues if they’re doing something strange or require the extra CPU.

If you already have a Pi 2, give it a go but if you’re buying then I’d recommend just getting a 3.

xmacex · 2020-10-19T09:06:51.313Z

Interesting, thank you @tomw. I don’t have an RasPi 2 (will try it out if I find one), but I think this is quite fascinating. I mean if people are excited about C-cassettes, 90s synths, and old banjos they found in the attic, why not RasPi 2s?

I have no idea know how much of the power of a RasPi 3 the norns programs use¹ either theoretically, or in how people actually use them. Will investigate…

¹ I mean “power” computationally, not musically or creatively speaking

coolcat · 2020-10-25T15:09:00.827Z

Hi all,

Correct parts, some soldering and resoldering, debugging and guess what - no more smoke Super happy
Many thanks for your help and support!
Special thanks to @okyeron, you are awesome!

Shield + case (minor mod from @okyeron design) + dyi grid (@okyeron design)
https://www.instagram.com/p/CGxTkA0hYf1/?igshid=eq3f51fh3kpy

eigen · 2020-10-26T18:36:31.638Z

Alright, continuing from my previous post.

I guess that my norns is alright, it’s just I might have been testing with the wrong device.

This post by tehn states that an 3.2 Vpp / 4dBu sine wave applied to norns’ input corresponds to 90% of the VU meter. With a signal generator I was able to reproduce the same thing.

My issue was that I was testing with a microKorg which I only got to output ~700-800 mVpp when pressing its keys with its volume maxed out. It’s documentation (p67) states that it outputs max +0dBu (2 Vpp). I guess I would need more than 1 single sine voice to attain this max theoretical output.

microkorg max output.bmp (1.1 MB)

So this weak 800 mVpp (versus 3.2 Vpp to attain 90%) seems to explains why my input seemed so low.

The CS4270 audio codec documentation (p26) gives an example of an input circuit with a voltage divider composed of 2 x 2k ohm, attenuating by half the input voltage.

The norns shield schematic has similar input circuit but with 3.3k and 1.5k ohm. This gives a stronger attenuation, of ~1/3.

So I assume that the example circuit is for +0 dBu circuits while norns’ is for hotter +4dBu ones.

I guess it’s safe to use a line-level preamp to boost my microKorg signal going into the norns (I was afraid at first seeing forrest’s comment).

I also assume that a preamp is even more needed to connect consumer electronics to norns’ input (e.g. a phone stereo jack) and get a decent enough level.

Am I right?

coolcat · 2020-10-26T20:20:11.492Z

Found first issues with my build.

Occasional volume variations - using official RPi power supply, no devices connected. Level goes up for a moment, then back to normal. Rare.
Low input level (same as @eigen?). Have to set input and monitoring level to max, but then I start hearing the buzz. Playing audio from Behringer UCA222 connected to Mac, also max playback level. What is you typical input / monitor level? Do you have to boost your source to avoid buzz?

zebra · 2020-10-26T20:32:12.193Z

I also assume that a preamp is even more needed to connect consumer electronics to norns’ input (e.g. a phone stereo jack) and get a decent enough level.

Am I right?

i’d say yes and no. at this late stage in the CE loudness wars, consumer levels are all over the place. at times, i have measured these for work reasons in a pretty serious lab setup. one of the more extreme cases i measured was a 2012 macbook air that put out over 3vpp at max volume with a very low output impedance (<5ohms.)

you are right that norns inputs are designed to handle +4dbu without clipping.

but there is also digital gain available on the inputs. it’s a high quality codec capturing at 24b, so you will not lose significant resolution or SNR by applying +4db or +6db of gain post-capture.

if, on the other hand, the inputs clipped at 0dbu, then you would of course need hardware attenuation to cope with hotter signals. so… i know which compromise i prefer

i should also maybe note that the the VU meter follows IE-60268 spec for PPM scaling. so 90% corresponds to -4dbFS.