Gameboy Mk3 - RPi3 + DPI screen + RTC diy [Completed!]

[razer.93]

Hi guys!
Here I'm showing my second build based on a raspberry pi 3 and a DPI screen. I have already built a GBZero with a standard composite screen I have never been satisfied of, so while designing this mk3 (yes, it's just for the raspi3) a dpi screen was kinda a must-have feature.
With the idea of building all around the screen I had to sacrifice some feature from the previous version such as the GPIO buttons, I2C and serial.

Here's a list of feature I'd like to implement in this build:
- A powerful RPi3
- DPI 18bit (unless I figure out an alternative way to the graceful shutdown pin necessity)
- Arduino PRO micro keyboard/peripherals managment
- Still include RTC support via I2C
- Battery meter of course
- Adjustable backlight intensity via key shortcut (still problems on that)
- Fancy status led(s)
- ...
I would need help to figure out how to driver a boost-converter with a digital potentiometer since I burned two boost converters last night with a trivial trimmer->digital pot replacement
Any suggestion would be appreciated!

I have almost all the pieces I need, I'm just waiting for the LCD, the audio amp and the 3D-printed frame, this is the progress so far:

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I cut the case, flattened the rpi3 and setup the graceful shutdown mechanism, wired the pro micro to the keypad and to the rpi itself; figured out how manage the DPI and the serial communication.

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Updates as soon as the LCD and the boost converter replacement arrive!

[Completed!]
Here it is:

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Completed with adapded/modified OSD, key shortcuts and automatic/hot-plug HDMI clone script (automatically detects when cabe is inserted).

If someone is interested here it's the sketch I'm using on the ProMicro:
https://github.com/vascofazza/GameBoy-MK3-Build

If someone is interested I published a little guide for display mirroring here:
https://sudomod.com/forum/viewtopic.php?f=20&t=4912

If someone is interested I made and published the SUPER free OSD here:

https://sudomod.com/forum/viewtopic.php?f=20&t=4927

Thank you all for the support!

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[moooarcuuuus]

I like your decision to add a RTC. I am also thinking about putting an RTC in my GbPi3. I want to show the time next to the battery indicator in the overlay. An Idea is an alarm timer...

[razer.93]

I like your decision to add a RTC. I am also thinking about putting an RTC in my GbPi3. I want to show the time next to the battery indicator in the overlay. An Idea is an alarm timer...

Do you have some nice overlay script in order to do that easily?

[moooarcuuuus]

Nope, so far there is only the idea. I use Kites SAIO (viewtopic.php?f=38&t=3295). His overlay osd is currently only a binary file. The I2c pins on the 32u4 can be used for the RTC and the epochtime can send one time via serial to the pi.

[razer.93]

Nope, so far there is only the idea. I use Kites SAIO (viewtopic.php?f=38&t=3295). His overlay osd is currently only a binary file. The I2c pins on the 32u4 can be used for the RTC and the epochtime can send one time via serial to the pi.

Yes, that was the plan! I have already wrote the script for the serial battery monitor and rtc. What about the keep alive pin? Can we use the activity led for example and redirect the power off overlay to that pin? In that way I could use a full 24bit color dpi screen..
Anyone knows if there is a 'correft' way to wire a digital pot to a boost converter for the screen backlight?

[moooarcuuuus]

I dont know. Kite solved the basic problems for me, his LCD works with 18bit. I just need to take care of my personal Gbz enhancements.

Good luck.

[salami738]

I like your decision to add a RTC. I am also thinking about putting an RTC in my GbPi3. I want to show the time next to the battery indicator in the overlay. An Idea is an alarm timer...

Do you have some nice overlay script in order to do that easily?

I think you should take a look at the pngview source code:
https://github.com/AndrewFromMelbourne/ ... /pngview.c
This tool is used by many to display a png image to the dispmanx display on the raspberry and is capable of displaying an OSD.
You need to replace the png loader with a font renderer to render your text as OSD.

[salami738]

...
- DPI 18bit (unless I figure out an alternative way to the graceful shutdown pin necessity)
...

You can enable the UART over USB in the arduino (https://techoverflow.net/2015/04/22/usi ... t-adapter/). Then you connect your shutdown pin to the arduino. If the button is pressed you send an info via UART to the raspberry. A script on the raspberry then shuts it down. I am currently testing that and can report back to you, if it works.

Because you are using UART over USB, you can use all GPIOs of the raspberry for your DPI implementation.
But you won't profit much from 24 bit mode of the DPI display, these displays don't have the necessary quality to see an improvement.

[salami738]

...
Anyone knows if there is a 'correft' way to wire a digital pot to a boost converter for the screen backlight?

I assume you use the display "LQ035NC111"?
According to the datasheet the backlight needs 18.6V - 21.0V and 20mA.

In my opinion you need a constant current, not a constant voltage source (boost converter). You can build it yourself or get a ready made lcd backlight driver chip, like: http://www.ti.com/product/tps61160. 1-output-channel, Input: 2,7-18V, Output 2,7-26V 20mA Current. Maybe @kite, or @ZeroBoy can confirm that.

The brightness is then controlled via PWM (f.e. from an analog output from your arduino) or via 1-wire protocol (arduino digital pin). See: http://www.ti.com/product/TPS61160/data ... LVS7915277

[razer.93]

...
- DPI 18bit (unless I figure out an alternative way to the graceful shutdown pin necessity)
...

You can enable the UART over USB in the arduino (https://techoverflow.net/2015/04/22/usi ... t-adapter/). Then you connect your shutdown pin to the arduino. If the button is pressed you send an info via UART to the raspberry. A script on the raspberry then shuts it down. I am currently testing that and can report back to you, if it works.

Because you are using UART over USB, you can use all GPIOs of the raspberry for your DPI implementation.
But you won't profit much from 24 bit mode of the DPI display, these displays don't have the necessary quality to see an improvement.

Thank you a lot for the hints!!!
Yes I'm already using the USB uart for all communications. I was referring to the keep alive pin in order to detect when the pi is in halt state (sd card unmounted). The default way is using the hardware uart TX pin or setting the tree overlay to a gpio pin. I was wondering if we count achieve the same result without using the gpios, but in fact if the 24bit depth is not really needed no problem.

I saw other projects (@tinkerBOY) using a boost converter but I will definitely look at your circuit!
Thanks again!