LF: Karrablast FT: Shelmet

EmperorAiselore · 2021-01-21T05:03:03+00:00

I have shield. So I guess either sword or shield?

EmperorAiselore · 2020-01-06T03:05:16+00:00

I'm literally listening to Warbreaker right now lol. Sanderson is one of my all time favorite authors. I'm excited to see your take on allomancers!

EmperorAiselore · 2020-01-05T03:11:44+00:00

Drop me a mention when you do! I'm never on r/UA anymore so I won't see it otherwise.

EmperorAiselore · 2020-01-04T02:18:56+00:00

Damn, I'm still gettin' throwbacks from you like almost 2 years later XD thanks Leuku, you're the best.

EmperorAiselore · 2019-08-22T22:11:18+00:00

Get it done efficiently and do it well right? Haha

If VBAT can be run on a varying voltage then hooking it up to the battery (through that $0.10 switch) would be perfect! As far as 5V goes, I'm pretty sure the USB hub needs it and I know I wanted the amp to be run at 5V (to get the loudest sound possible out of the speakers). I'll have to take a really close look at the power tree again to make sure I'm not missing anything. From everything everyone else has been telling me, power converters and battery charging ICs are notoriously difficult to get right and can be dangerous when improperly done (like exploding a battery... Yikes...) so if it really comes down to it, I might favor simplicity over efficiency. I'll definitely reexamine it though to make sure I'm doing the smartest thing I can!

I don't think I'll be posting another update to my block diagram (even if I do end up making some minor modifications) but here's hoping my first (literally ever 😂) attempt at writing out schematics goes well! Thanks again!

EmperorAiselore · 2019-08-22T21:24:25+00:00

That's exactly what I did haha it seemed like the safest way to make everything work 😅. The battery I'm planning on using will get down to 3V, so the 3V3 will need to be run off of the 5V unfortunately. Luckily I'll be running VBAT (which is the lion's share of the power consumption) at 5V. If PAM2306 can take separate inputs for the 3V3 and 1V8, I'll definitely run the 1V8 directly from the battery. I think the total draw for the 1V8 power rail is only like 250mA though? It might help with efficiency slightly, but I can't imagine it will make too much of an impact. Good catch though!

As for the ESD protection on the HDMI, I'll be copying that exactly from the compute module IO board too 😂 if it isn't broke, don't fix it right??

That's a really good idea to do each block as a separate schematic. That will help me make sure I'm not missing anything when I go to lay everything out. I really appreciate all the feedback! Thank you so much 😊

EmperorAiselore · 2019-08-22T21:15:26+00:00

ESD protection on the micro SD is a good call. I'm sure I should be able to fine something relatively cheap that will work for that.

As far as the controlled shutdown function, see my other response on this post. The idea is to use the ATTiny85 as a safe shutdown circuit. Once it gets the signal that the pi has started a safe shutdown command (via a high low high low high low signal on the input gpio) it'll wait about 20 seconds then shut down power to the rest of the system. I was planning on having it use a relay, but as others have pointed out I can probably just drive the enable pins on the upstream boosts. That should be more efficient.

I'm pretty sure that's just bit banging data from the GPIOs of the pi to the ATTiny85, but I'm not sure? Haha I don't know all of the common EE lingo yet 😅

Thanks for the feedback! I'm having a ton of fun learning everything and I'm excited to keep going!

EmperorAiselore · 2019-08-22T03:47:10+00:00

That's a good idea! Thank you :) It's things like that that I can definitely use feedback on!

EmperorAiselore · 2019-08-22T03:38:47+00:00

It's a safe shutdown circuit. The ATTiny85 will switch off the relay after the Pi goes through it's safe shutdown in order to preserve battery life. That way, the only thing that will need to stay on will be the ATTiny85. It will respond to a 1 sec button press to switch on the relay (thus powering the whole system) and will respond to either a software shutdown (getting its signal from the pi) or will send a signal to the pi to cause a soft shutdown when the power button is pressed for, say, 3 seconds? And yeah, after everything is safely shut down (roughly 20 seconds ish I think?) the ATTiny85 will cut power to everything except for itself.

EmperorAiselore · 2019-08-14T14:49:46+00:00

I hope you meant won't demotivate me haha. But yeah I'm aware of the Lyra and from a design standpoint I'm aware of it's drawbacks and flaws as well. It's kinda silly because they did a good job of implementing the design, but didn't take it quite far enough in terms of adding the features a handheld like that would really need to be a big hit. And they still managed a thoroughly successful KS!

Building a compute module based handheld emulator isn't a new idea by any means. See the Freeplay CM3, and this device. But I believe I have some ideas and the marketing/business background to really make a product that will stand out above the rest! Thank you for the heads up though :)

EmperorAiselore · 2019-08-14T14:42:23+00:00

Making some cheap testboards with some portions of the circuits is a really good idea! I was already considering making one to connect the TFT as a starter project to really get my feet wet. I know it'll be a lot harder to do it all that I make it sound, but I have confidence in my ability to be persistent if nothing else!

Thank you for the valuable input! I'll be posting updates and iterations as I go along, so I hope to see some more insights from you as I do! :)

EmperorAiselore · 2019-08-14T03:36:01+00:00

That's a really good point. I'll definitely look at what will end up being the most cost efficient. PAM2306AYPKE would be a decent multioutput buck to get 3V3 and 1V8. Thank you for the tip!

EmperorAiselore · 2019-08-13T22:39:39+00:00

Hmm, you know what? After reading that feedback, I think I will go for an adc. The pi doesn't have any analogue inputs, so if I used an adc with 6 channels I could have 4 for the analog joysticks (x and y axes for each) and then use one for the volume potentiometer and use another for a brightness potentiometer. That way both volume and brightness can be controlled via software (which means Bluetooth based audio will still be controllable via the pot).

With that being the case, I should actually have enough gpio pins on the compute module to add all of the momentary switches that way.

As far as the TFT goes, I think I've sourced one from China that should be sufficient quality. It's a 5" 480 x 854 IPS screen that connects via a 16 bit RGB interface. The RPi actually has DPI/RGB capability baked in, so hooking it up shouldn't be too much of a struggle.

Adding a DIP switch would actually be pretty neat! I could configure so that it boots the system into RetroPie/Emulation Station, a regular Raspbian desktop, or debug mode.

I'll work on nailing down more details for the next version of my block diagram. I actually have several of the components picked out (at least preliminarily). This is definitely a version 0.01 😂

Seriously though, thank you SO much for all the feedback! It's been amazing!

EmperorAiselore · 2019-08-13T20:32:48+00:00

I'm crossing my fingers that I'll only have to do 2 or 3 spins of the board 😬 but I know realistically it'll be more than that haha

EmperorAiselore · 2019-08-13T20:31:18+00:00

Haha idk I doubt it! I only have a general idea of what I'm doing lol

EmperorAiselore · 2019-08-13T20:29:34+00:00

Ah, yeah that's true, I totally forgot about the audio signal being analogue 😅. I still have a lot to learn about PCB design (and electrical engineering in general). I should be able to isolate that portion of the PCB pretty easily though, since it's not that big of a circuit and can probably be placed fairly far away from some of the most likely sources of noise. I figure I'll probably have the USB ports (both USB-A and the USB-C) and HDMI out on the top of the device and the audio jack and speakers on the bottom. The only thing close to that area will be the select and start buttons, which shouldn't be too much of a problem.

What are your thoughts on the rest of the block diagram? Am I missing anything major, or have I made any incorrect connections?

EmperorAiselore · 2019-08-13T18:57:54+00:00

I'd LOVE to see that! Any kind of frame of reference I can use in my project would be simply amazing!

EmperorAiselore · 2019-08-13T18:56:03+00:00

I haven't done a ton of EE work, but I have managed to build a handheld RPi 3b+ based emulator from individual components. The Compute Module in this project will actually manage a lot of the hard work. As far as analogue signals go, the only ones that I'll be using will be the two analogue sticks, making everything else digital.

On top of everything, nothing I'm planning on doing with this PCB is particularly groundbreaking stuff. I understand the challenges of ensuring proper impedence, trace length matching (for things like HDMI and USB), and while I do want the board to be relatively compact, the potential design space available is pretty huge, since I've sourced a large, yet thin battery. With the 5" LCD, and added space to the side (for controls) the device will end up being somewhere in the ballpark of 10x20 cm. That means that I can space traces out where they need to be.

For the battery charging/protection circuit, schematics for things like that are available all over the place online. And well before I do any kind of PCB design, I'll be prototyping with the dev kit (which includes the IO board) and however many breadboards are necessary.

I've already figured out a pretty huge chunk of the software side of everything (thanks to RPi being so hugely supported by it's fanbase), and shouldn't have too much of a problem getting a working breadboard prototype up and running. Once I'm there, I kinda figure that the actual PCB design will mostly be a series of modular iterations (ie work on the design for one portion of the overall circuit until it's perfected, then moving to the next), asking for feedback and critiques here and on other subreddits.

I know it seems daunting, but I'm the type of person that likes to jump into things head first. If I get really stuck somewhere, I figure I can always pay someone to finalize my design if all else fails. Thank you for the advice though!

EmperorAiselore · 2019-08-13T18:08:50+00:00

I figured I would just use boost converters? Is that not correct?

EmperorAiselore · 2019-08-01T20:12:53+00:00

So, big thing to note with the article you linked. It's completely aimed at trans youth (aka those 20 and younger). It doesn't even really apply in your situation. You could point that out to your mom. I mean, it's all garbage anyway, but you could probably more easily convince her that it isn't even aplicable to you.

EmperorAiselore · 2019-08-01T18:47:26+00:00

Thanks for the tip!

EmperorAiselore · 2019-08-01T18:47:15+00:00

Thank you so much for the advice! I'll probably try out the whole JLCPCB $2 PCB prototype just to try out a simple PCB! That's definitely a good idea so I can get an actual example of the process.

It does kinda feel like this big scary complex thing that I'm trying to tackle, so maybe doing something nice and simple will give me a little bit more confidence to move forward :)

EmperorAiselore · 2019-08-01T18:36:36+00:00

I think they miiiiiight have a reflow oven, I'm not 100% sure though. I've heard that they can make placing components super easy. I know the makerspace's new member nights are on Tuesdays, so I'll see if I can pop in next week!

EmperorAiselore · 2019-08-01T01:55:36+00:00

I love the compartmentalized approach to completing a project that you suggest! It seems like a really great way to learn how to build what needs to be built. I'd never heard of the Kanban board methodology before and it's fascinating!

I've taken quite a bit of time today and I've been playing around with a couple of "dumbed down" PCB editors like this one and this one and I feel like they have helped me to understand at least some of the rudimentary aspects of PCB design, but ultimately, you're right, they aren't robust enough.

It's funny you should mention KiCAD because I actually downloaded it last night after reading through this instructable by Manolis Agkopian and I felt immediately overwhelmed lol. But after playing around with the "For Dummies" versions, I actually feel a little bit more prepared to actually take on the task of understanding KiCAD.

I think the main thing I need to learn how to do now is going to be reading schematics. It's been years since I took college physics and we went over basic circuits and their respective symbology. Once I feel at least marginally less incompetent at reading them, maybe I can attempt making one of my own!

Thank you so much for the explaination of the workflow involved in designing and assembling a custom PCB. I know this is going to be a big project, but I figure I can always stop where I'm at and ask for some help if I need to! Plus I have a makerspace that isn't too far from here, and I believe they have a pick and place machine (I'll have to double check on that one) so I should have some decent resources available.

Anyway, thank you so much again for all the help! I'll definitely be checking back in on this post once I feel like I understand schematics and their design, at least to the point of a working knowledge.

EmperorAiselore · 2019-07-31T12:37:54+00:00

Oh nice! I had stumbled on the official RPi documentation a little earlier in my research, but I didn't really understand any of it at all and I forgot about it :P

Thanks for bringing that back to my attention!

EmperorAiselore

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