Author Topic: I'm designing a new handheld  (Read 902 times)

flatmush (OP)

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I'm designing a new handheld
« on: February 21, 2019, 07:35:53 pm »
It's been a while since I've posted here, some of you may remember me from the early days of the Dingoo A320 where I worked on the Dingoo SDK for the official firmware.

For a while I've liked the idea of making a console, but it's been quite hard to acquire components and design something for a reasonable price, but a few things have made it possible recently:
1. PCB fabrication costs are very low now.
2. HardKernel have released cad files for their PCB which allows using an existing enclosure easily.
3. The STM32H7 microcontroller runs at 400MHz and allows execution from SDRAM.

I'm sure you can see where this is going; These things combined allow for a hobbyist to design a console about as powerful as the Dingoo A320 relatively cheaply.

To cut to the chase, I've already designed the PCB for this thing as you can probably see from the image attachments. The design is also fully open-source, you can download/contribute the schematics and PCB layout from here: https://gitlab.com/flatmush/f100-hardware

The basic specs are:
400MHz STM32H7 MCU with 16KiB I/D Cache
1MiB Internal SRAM
32MiB 16-bit 133MHz SDRAM (Upgradable to 64MiB, potentially overclockable to 200MHz)
320x240 18-bit 60Hz 2.4" LCD (Hardware dithering to 24-bit, may support 120Hz refresh)
Hardware 2D acceleration & JPEG decode
12-bit Audio Output with hardware volume control
2MiB Internal Flash (for bootloader really, all data will be on microsd card)
4-bit microSD Card Interface (50MHz supported, potentially overclock to 100MHz)
PWM-RGB Status LED

Obviously I know this isn't a dream machine because the odroid-go shell limits the button layout, but if all goes well with this then I might try something more advanced.

My only concern currently is that the routing is not good enough for the SDRAM, but from what I've read it shouldn't be too critical.

I'd love to hear feedback.



« Last Edit: February 21, 2019, 08:57:56 pm by flatmush »

Dr_Bunsen

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Re: I'm designing a new handheld
« Reply #1 on: February 25, 2019, 11:10:57 pm »
Will you add a headphone socket? Also, are you going to spec a 60fps screen? The Odroid Go is quite limited in these two areas.
My Portable Devices: Game Gear, PSP 3000, Nvidia Shield Portable, GPD Win, Coolboy RS-97, PAP KIII Plus, GCW Zero

02k0

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Re: I'm designing a new handheld
« Reply #2 on: February 26, 2019, 12:06:01 am »
2 action Button?
It need 6 action Button.

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pcercuei

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Re: I'm designing a new handheld
« Reply #3 on: February 26, 2019, 02:53:43 am »
What would the 1MiB internal SRAM for?
You could maybe also scrap the 2 MiB flash, if the SoC is able to boot from micro-SD directly.

flatmush (OP)

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Re: I'm designing a new handheld
« Reply #4 on: March 02, 2019, 11:45:51 pm »
Hey All,

Sorry for the late reply, been working pretty hard on getting this finished.

Will you add a headphone socket? Also, are you going to spec a 60fps screen? The Odroid Go is quite limited in these two areas.

I looked into this, but it's pretty difficult to do:
Code: [Select]
I had a look into a barrel jack for headphones, however due to the height constraints of the board, it wouldn't be possible to just footprint it. Nothing can be more than about 2.5mm high on the back of the board where all the components currently are.
There is one solution which is to get a jack which fits in a slot cutout (6mm by 13mm), however this brings some issues of it's own. The only place it could possibly fit is just above the A button, however the cutout would reduce the integrity of the board.
The cutout for these jacks is also a complex shape which may be hard to manufacture and requires further through holes.
While it is possible, I chose not to do it, because I don't want to risk making the board too weak.

2 action Button?
It need 6 action Button.

I agree. This is my first PCB or project like this, so I don't expect it to be a dream machine, but hopefully if this goes well then I will be able to design something with wider appeal.
For now it's stuck with 2 buttons cause that's what the ODROID GO had: I looked into footprinting 2 more buttons so that people could add them by drilling a hole, but unfortunately there's no space in the ODROID GO shell for that.

What would the 1MiB internal SRAM for?
You could maybe also scrap the 2 MiB flash, if the SoC is able to boot from micro-SD directly.
The 1MiB of SRAM is just because the MCU I chose happens to have it.
There are a few uses for it though, it's very fast ram which has the same access time as the cache, so obviously it can be used for small fast pieces of code or lookup tables which could speed programs up.
There's also a section of ram which keeps it's contents during poweroff which would be useful for saving state, or faster boot.

The 2MiB of flash is part of the MCU, there's no way to remove it. It's fast flash which can directly be executed from so it's perfect for a bootloader and potentially commonly used parts of the OS. Especially stuff like bitmap fonts and logos which would be rendered frequently.
There is a version of the chip which is cheaper and has much of the flash removed, which I would consider using, however it's not available in a qfp144 package, so it's not really an option for now.

I hope I'm not breaking forum rules by posting a link to another forum, but since there's much greater interest in the ODROID GO forum for the hardware side of things, you'll find more detailed updates here:
https://forum.odroid.com/viewtopic.php?f=158&t=33936

bamboori

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Re: I'm designing a new handheld
« Reply #5 on: March 08, 2019, 01:46:11 pm »
I'm wondering why you are limiting yourself to the odroid go shell? with 3d printing widely available, a custom shell shouldn't be a problem.

flatmush (OP)

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Re: I'm designing a new handheld
« Reply #6 on: March 11, 2019, 09:39:09 pm »
I agree, but have to start somewhere. If this goes well then I'd like to design something a little more comprehensive.

gibberish

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Re: I'm designing a new handheld
« Reply #7 on: April 08, 2019, 12:45:37 pm »
i know it's likely too late now, but the RetroMax shell is really very good. it can be had for ?10 ish from Aliexpress. it supports 4 face buttons and 2 shoulder buttons.

either way, best of luck with your project!

02k0

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Re: I'm designing a new handheld
« Reply #8 on: April 09, 2019, 12:33:54 am »
Project progress?

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