My first midibox project...

[Artesia]

Just got the pcbs from mike for building 1x Quadra Sid, 1x MBFM, 1x midisequencer & a JDM V2.

Here's the first of the projects finished; the JDM prommer. amazingly it worked first time it was plugged in & programmed 7 pics without a hitch ! ..im sticking with this one for now - however i could help to test the new prommer too i guess.

As you can see, i chose to use a proper programming socket (12 euro from voti.nl). This was done to ensure a consistantly reliable connection throughout the jdm's life & more importantly to minimise the possiblity of stressing or breaking PIC pins.

Could i please make a request for the updated/newer programmer revisions to include enough extra pcb space to use one of these sockets as a option ? :) ..as i had to relocate some of the components to the underside.

Below is the beginnings of the three projects; and a evenings work.

...am looking forward to posting some finished projects soon :)

[ESPguitar]

Hi, cool:)

Since you're a bit more into programming and stuff.. Can you tell me about how you do it, what can the chip control and so on??

Thanks,

RB

[Screaming_Rabbit]

Since you're a bit more into programming and stuff.. Can you tell me about how you do it, what can the chip control and so on??

... this is just burning the bootstrap. Now it can't do much... he later will programm the MIOS application... the one which does what he wants it to do  ;)

Greets, Roger

[smashtv]

As you can see, i chose to use a proper programming socket (12 euro from voti.nl). This was done to ensure a consistantly reliable connection throughout the jdm's life & more importantly to minimise the possiblity of stressing or breaking PIC pins.

Could i please make a request for the updated/newer programmer revisions to include enough extra pcb space to use one of these sockets as a option ? :) ..as i had to relocate some of the components to the underside.

I ran into the same issue, the easy way is to stack standard sockets under the ZIF socket, get it up off the board and out of the way a bit.

Best!

Smash

[Artesia]

..true, that is a solution ..allbeit a another work-around :)

[Artesia]

Heyas  :D

...well i've got the guts of a mios sid setup wired & ready to go - but as below i am getting nothing out of it ! ..the luck ran out ;) :/

Its drawing current (160ma with display off) but there appears to be nothing going on.

Also when checking the board for signals, the only one the scope picks up is stray emissions from the lcd back down the data cable (btw tried a 2x16 display before also).

Have additionally tried changing the crystal for the pic & tried afew pics with different programs burnt on them.

Any pointers on debugging this ?

Also below here is a solution, allbeit a fiddly one - for using the far more affordable 74hc595 SMD chips. Someone like the idea of making some little chip carriers outta proper pcbs for this application ? :) ...and maybe itd be a cool idea to integrate SMD pads into the pcbs of the modules that use these chips ? :)

..well thats all for the min; i gotta go...

[TK.]

Debugging with a scope is really simple: check the signal at the oscillator pins (OSC1 and OSC2), it should be 10 MHz, the amplitude is ca. 2-3 V so far I remember but it doesn't matter here - only the frequency is important, so long the clock is not available, nothing else will work.

SMDs: are you sure that this is a cheaper solution? The DIP version of the 74HC595 costs 0.33 EUR at Reichelt.

Best Regards, Thorsten.

[Artesia]

hmm.. yup thats what i found with the crystal - no signal there; should of meantioned that specifically. mustve done something really stupid somewhere :] ..the voltages for the pic mesure right, there does not appear to be any shorts or missing bits. and im reasonably certain that its the right caps & crystal for the oscillator. hmm...

i presume the  following combination is good for a oscillator circuit in this specific application: ?

rswww.com:  [829-277] 33pf disc ceramic cement coated capacitor.

rswww.com:  [226-1746] 10mhz CMAC  HC49/4H 30pf crystal

...as for the 74hc595's ..hmm should of looked at reichelt when buying parts :/ :) ..not too bad a price there. When i bought these chips, rs did not have any of the more sensibly priced dip's in. ..however now they do have them in at 0.47 EUR. if im ordering more than a handful in the future, ill be going through reichelt.

Update:

Done the sensible thing and tested against another board i had not finished - same result. so its some sort of oversight which will probably affect them all i guess.

Added to that - just stuck the scope on somthing else with a crystal in; to confirm that  i was taking a correct ground reference for the crystal. a very definate trace from a usb device. most certainly no oscillation from the pics

just tryed some other caps for the oscillator, no change on that one either.

also stuffed the pic in the jdm to see if itd read and program ok ...no problem there it would seem. so the chip should be ok electrically. also even if it was not programmed, it should still tick over the oscillator.

hmmm.. guess ill sleep on this & see if i wake up with more of a clue as to what iv'e overlooked...

[Artesia]

i'm gonna sound really stupid now ;)

I'm a little stumped; anybody got an idea what could result in no crystal oscillations when the chip (and most other things) appears to be fine ?

Thanks.

[TK.]

Just for the case that you want to feel more confident with the crystal - exactly this type was successfully tested by Preben_Friis, see:

http://69.56.171.55/~midibox/forum/index.php?topic=1338.0

Best Regards, Thorsten.

[smashtv]

-sometimes- crystals on battery power don't like to start oscillating.....something to do with the power source being so clean......

Crystals are like old dying electric motors in a way......

Bad motor: apply power, and it hums and heats up but does not turn, spin it (help it start) and it might run for years, as long as you don't stop it.

Crystal: sometimes need to see a "glitch" before they start.....

I know this sounds crazy but try touching (with your finger) various connections around the caps with it powered, the crystal might just start up for you (seen these symptoms with others).

Best

smash

[Skunk]

Hey Smash, 

great explanation for the crystal behaviour! Never got it in my 25 years electronics life. Even a professor can't do it better. If You don't have a copyright on this, I'd take it over in my private technical explanations directory. Our next generation will certainly have fun reading Smash's newbie school lessons.  ;D

Cheers,

Skunk

[smashtv]

Our next generation will certainly have fun reading Smash's newbie school lessons.  ;D

hehe hopefully I can work out a rosetta stone or magic decoder ring before the next generation, so they can easily see through the overly verbose answers (never thought I would be a novelist!), run-on sentences, and my terrible daily flogging of english grammar......  ;D

Where do ya live/what country?  (trying to figure out what postage will cost me to mail you an xtal and caps)

best

Smash

[Artesia]

Gawd dammit :) ..guess what. iv'e been running it on a lead acid battery & the thought did cross my mind - though thought nah ! ...who'd design a pic with oscilator circuit thatd bitch about been run on the move ? ...out with the powerpack i guess :) Will give that a try - good explaination btw !

also a note about scoping the crystal - i did in the end happen across a small trace with regular spikes at what should be about 10mhz spacing - which are clumped togeather in squarewave like envelope packets. which concurs with the trying to start theory :) notibly this pattern was not altered when the cap values were tweaked (head scratch!).

hmm maybe itd be benificial to make a ripple injector to allow portable use ;) - kind of ironic that theres all those extra small value caps on the pic board n' all.

btw - with regards to the crystal thread (thanks tk - i should read old threads more ! :); I tryed some of the other cap values that were suggested for use by others with these very crystals & didnt get very far :/ ..ah well, on with the above approach i guess.

Update:

Re smash:

if you meant my address.. :) ..im in the midlands in the uk. I may well have this cracked soon tho. in anycase a known good oscillator set is a useful testing tool. ta.

[Steven_C]

I have powered midibox projects off batteries with no probs before... See my posts in the tested crystal thread to see which crystals I used. (sorry if I missed something, I'm in a hurry and haven't read this whole thread... yeah I know its not good forum ettiquette...  :P)

[Skunk]

Hi Smash,

livin in good old Germany. No hurry to send me a xtal and caps, I've more than enough in my black boxes. But you could answer my PM since you could earn some money doing this!  8)

Cheers,

Skunk

[Artesia]

Just seen a intersting & simple way of kick-starting a crystal osc. Attaching a small capacitor between one of the crystal pins & the +5v rail. Found this in a furby schematic ! ...tried it to see if itd resolve my hardware headaches; no such luck - though maybe with other midiboxers it'll be enough to allow their boxes to run on DC reliably.

Waiting on some more crystals to try now...

[Tanstaafl]

I have built 4 midiboxes over the last couple of years and am working on 2 more now.  I have used the ceramic resonator

at the link below without any problems.  they cost  $00.45  USD each.  not sure why the expensive crystal/capacitor is needed.

http://www.ecsxtal.com/pdf2/ZTT.PDF

accuracy has not seemed to be a problem with this... my moog modular midibox has 3 cores and timing seems to work fine.

my next project will be MBSEQ, we will see if  my setup is accurate enough.

BTW... since these things have 3 legs, I modified the PCB of the core to accomodate this resonator, oh and it mounts on the 'parts' side of the PCB, not underneath.

gb