Matt's Pocket Build - WIP - Will take me a while

[mattc]

Update;

The USB hub & Audio work flawlessly and have fantastic sound quality. Really impressed.

Still waiting on the wi-fi modules from China and I've been let down on the LCD supply again..... still struggling for a screen on this.

In the meantime I think I've solved the USB power/Host problem, leading to a single port that will charge and act as a standard USB port. I've integrated an always on 3v3 20mA supply in order to have a watchdog micro-controller in charge of the system, monitoring the battery and power switching circuit. I've got another PCB coming in to test this section of the circuit.

Here's the PCB...



It's quite small and literally does all of the above and includes over voltage protection, instant on to cope with a totally discharged battery and 1.2A charging.

Status so far:

Power Regulation - CM3 supplies done
CM3 working fine - booting retropie
18 & 24 bit DPI working perfectly
USB - 4 ports available to CM3
Audio - Working perfectly to speakers & headphones with auto speaker cut off, analog volume control working.

In progress:

Battery Charger/Host USB-OTG Power/LDO Power - Design complete - Boards in Production & Components Ordered

To do:

Finalise Safe shutdown - waiting on new charger/power board.
PWM Dimming of LCD Backlight - still toying with inclusion of Arduinio and consolidating watchdog/controls/dimming/other all in one place.

[mattc]

Another little update.

All my components are in, I've sourced yet another screen and waiting for that to arrive from China.

My test board above for the power is expected to arrive on Monday, so next week should see some firm progress.

Also realised I've not posted any pics of anything actually working

So, here's 18 bit dpi running from a ras-pi 3 using a dpi adapter similar to one that kite built a while back:



I built this quickly to play with DPI configs, the picture doesn't do it justice.

So I then transferred this to my 'franken-module':



Pardon the extra wiring, I messed up my supply lines on the test PCB, but hey.. it's for testing

So I have a working CM3, working 24 bit DPI, Working 4 port USB hub & USB sound.. Hopefully a consolidated, charge/host port PCB arriving to test.

Been thinking about controls/backlight dimming/Safe Shutdown and bought this to play with whilst I wait for everything else...



It's my first real play with a full Arduino so a lot of reading to do.

Making progress, slowly... But I will get there.

[mattc]

Another small update;

The new PCB's for my new power circuit testing arrived this morning, I soldered one together:



So far so good.

It switches seamlessly between charger & battery power, presents a constant VBAT, 3v3 for my watchdog and.....

When you pull out the power & plug in a USB device.... VBUS presents 5V! This is a big success for me. It means a single USB port that charges (@ 1.2A) and can be used as a host port when running off the battery. This ultimately leans less case modding and a more 'stock' look.

I've got to still hook this board up to my USB Hub board and prove it once and for all, but the voltages all work .

I've found yet another screen candidate.. 2.8" this time which will unfortunately mean some case modding to fit it in. I'll see how it fits then hopefully be asking all sorts of questions on here of you good folk for some guidance to design a 3d printed screen bracket.

I'll weave this design into the main board later, along with some other bits I've got pending and then I'm literally waiting on the screen and continuing to play with the Arduino.

[erik_gee]

Nice keep up the work !

[erik_gee]

Another little update.

All my components are in, I've sourced yet another screen and waiting for that to arrive from China.

My test board above for the power is expected to arrive on Monday, so next week should see some firm progress.

Also realised I've not posted any pics of anything actually working

So, here's 18 bit dpi running from a ras-pi 3 using a dpi adapter similar to one that kite built a while back:



I built this quickly to play with DPI configs, the picture doesn't do it justice.

So I then transferred this to my 'franken-module':



Pardon the extra wiring, I messed up my supply lines on the test PCB, but hey.. it's for testing

So I have a working CM3, working 24 bit DPI, Working 4 port USB hub & USB sound.. Hopefully a consolidated, charge/host port PCB arriving to test.

Been thinking about controls/backlight dimming/Safe Shutdown and bought this to play with whilst I wait for everything else...



It's my first real play with a full Arduino so a lot of reading to do.

Making progress, slowly... But I will get there.

I'm looking into using dpi screens on a few projects, is there a good starting point you would recommend for research? Not sure how to get this up and running as I'm unfamiliar with this type of screen.

[caste]

Awesome, I'm really stoked to see more CM projects popping up.

[mattc]

I'm looking into using dpi screens on a few projects, is there a good starting point you would recommend for research? Not sure how to get this up and running as I'm unfamiliar with this type of screen.

The single best source of info for me was here:

http://blog.reasonablycorrect.com/raw-dpi-raspberry-pi/

The bit about device trees is unesecarry now, as there are ready made 18 & 24 bit overlays for DPI.

Also have a look at the pi foundation github page:

https://github.com/raspberrypi/document ... /README.md

and the LCD Datasheet:

http://www.distarltd.com/TFT/2/LQ035NC111.pdf

It really helped me a lot that @kite had already trail-blazed using this screen and worked out the config.

[erik_gee]

I'm looking into using dpi screens on a few projects, is there a good starting point you would recommend for research? Not sure how to get this up and running as I'm unfamiliar with this type of screen.

The single best source of info for me was here:

http://blog.reasonablycorrect.com/raw-dpi-raspberry-pi/

The bit about device trees is unesecarry now, as there are ready made 18 & 24 bit overlays for DPI.

Also have a look at the pi foundation github page:

https://github.com/raspberrypi/document ... /README.md

and the LCD Datasheet:

http://www.distarltd.com/TFT/2/LQ035NC111.pdf

It really helped me a lot that @kite had already trail-blazed using this screen and worked out the config.

Thank you for those links! I believe I've seen the first one while nosing around in google haha I appreciate it.

I am a computer engineering student, so I know my way around datasheets and whatnot, but the item-specific terms I am a little confused with. I understand the concept of 18 or 24 bit color, but what exactly is the "overlay" you speak of?

Also, is there a post kite has made with more information ?
Sorry for all the questions, this is just one of the things I've had my eye on for a while but didn't quite have the knowledge to complete

[mattc]

In the simplest of terms, the overlay reconfigures the GPIO pins to perform a specific function. In this case it switches them to ALT2 mode.

If you pop:

Code: Select all

dtoverlay=dpi18

into /boot/config.txt, the system will be configured for the necessary GPIO to enable 18bit DPI.

There's also a 24 bit overlay that eats all the GPIO pins.

[erik_gee]

Ah that overlay, sorry for the simple questions haha thank you very much !