been working on a project/pcb for a bit now off & on… and I think Im finally done with it…and ready to send off for PCB’s to be made.
However… since I just ‘play’ like I know what Im doing here…LOL… Id appreciate it if some other more experienced members here could take a and see if they can find any errors/problems/mistakes I made… that need to be corrected before sending out to fab house.
To give a bit of a summary on the project… there were some requirements/rules I needed to abide by…
1.) minimal Arduino circuit (minimal as I can get it and still be half way stable)
2.) no voltage regulator
3.) micro SD card
4.) limited components on top of pcb (main chip, 5 x green leds, 3x red leds w/resistors…these red led resistors had to go on top for lack of space)
5.) size is UBER tiny… (not much bigger than a micro SD socket itself
6.) had to have a custom PCB shape to retro fit into an existing prop/item.
- there is an INNER circle (orange I think)… this is only DRAWN there to give me a visual on where I can place things…and where I cant on the top of the PCB… anything on TOP outside of the orange inner ring/circle is a PAD ONLY… for flashing the chip and FTDI communication… no components on the TOP side, outer ring/circle area it will have a ‘bezel’ over it… that circle shows the ‘window/opening’ that will display the main chip.
reference pic: (mock-up only)
- this PCB was design to be used with the SimpleSDAudio lib posted here… that does PWM audio output on PIN9
pic of how the microSD fits in on this… (and how it east up my damn space too!) LOL
anyways…so after mocking up similar on breadboard… and testing out some things, I moved onto wrapping up the PCB…
I would appreciate a second set of eyes to look it over if anyone is bored/interested.
this thing has been a challenge in CRAM-FU!.. thats for sure… LOL… but fun none-the-less…
couple things to check perhaps:
1.) the C6/C7 caps… are they even working/effective like I have them? (too far away? not correct implemented for coupling caps?)
2.) R1 resistor for set-up… all that correct? RESET/DTR…etc…?
3.) maybe board is so small/traces so small… I dont need a caps C6 & C7?.. just the MAIN 22uF cap comign off the main battery input is enough? (maybe the 22uF is to high even? not really a data sheet on a voltage regulator to read to get a ‘value’ to be used)
Here are the .sch & .brd file (Eagle)…
please let me know if there re FLAWS that need to be changed:
***one side thought I have been having is… ‘future usage’…
I know the current audio quality is not ‘great’… its staticy… and VERY loud… its more of a novelty addition, and better to have ANY sound then none)
that being said… I had been reading that you can combine D9 AND D10 for dual PWM output… better quality?
And the SimpleSDAudio lib/page has some example of using D10 as an extra output for the audio…
there is of course NO ROOM on the pcb for anything else… but was thinking it might be worth looking into to add a D10 pad broken out (and of course move the SD CS pin to D4)… just in case anyone wants to hack this pcb later on for better quality?
to re-iterate I ONLY have a 100uF cap on the D9 audio output pin… nothing else, and the quality is ‘ok’ at best (still static)… maybe changing the cap… and perhaps adding a resistor would help get better output? (and time better spent then trying to add in a D10 pad?)
let me know!