Propeller 1 in an 8 pin DIP

Tubular · 2014-03-03 17:01

I've wanted for some time to package the prop into a minimal 8 pin DIP format, and finally got around to making it.

This is an oshpark 4 layer board with prop qfn and passives on one side, and regulator, eeprom and xtal on the other side. An 8 pin DIP socket header brings out breadboard friendly pins.

One of the pins is "tv out", using the standard 3 resistor dac. The prop plug connects on the other side, ie

       _____
P30 --[o    ]-- +5V
P31 --[     ]-- SDA
RES --[     ]-- SCL
VSS --[_____]-- TV OUT

This board has an outline about 0.8 x 0.55", but the "core" is about 0.6 x 0.45" . Thanks to Phil and Jmg for the xtal / txco part numbers.

mindrobots · 2014-03-03 17:11

OK, that's pretty wild!

Way to push (shrink?) the envelope!

msrobots · 2014-03-03 17:25

Funny, but for what application?

serial, I2C and tv. Hm.

Enjoy!

Mike

jmg · 2014-03-03 17:37

Tubular wrote: »

I've wanted for some time to package the prop into a minimal 8 pin DIP format, and finally got around to making it.
This board has an outline about 0.8 x 0.55", but the "core" is about 0.6 x 0.45" . Thanks to Phil and Jmg for the xtal / txco part numbers.

Very Cute.

Given the PCB is larger than DIP8, why not extend the 0.3" stitching to allow DIP14/DIP16 superset choices ?

Tubular · 2014-03-03 17:50

@mindrobots, it could go a bit smaller (0.45" wide), but I don't really want to risk sanding it while it works. Perhaps later!

@msrobots, the current application is driving a couple of ws2812b led strips (via the i/o on ends).

@jmg, yes I wanted to make sure the core is compact (~ 10mm square), then it can be extended out to 14/16/28 pins, and all the smd components may fit on one side then.
I think a 14 pin version with VGA output (or gpio) along one side, and P0~2 (usb / gpio) and prop plug on the other side would be a good DIP14 variant.

I'd like to think this would be a strong contender in the "ratio of 32 bit cores to pins" class (1 core per pin)

Cluso99 · 2014-03-04 18:25

Very nice. If you change the pcb, you might consider placing the sda/scl/tv in the eeprom format ie tv to pin 7 (was wp) so that its similar to the standard 8 pin chips.

P30 --[o    ]-- +5V
P31 --[     ]-- TV OUT
RES --[     ]-- SCL
VSS --[_____]-- SDA

Cluso99 · 2014-03-04 22:01

Presume you are using a 5MHz xtal?
I am curious, what is its size and pn?

I going to get some of these 12MHz 3.2x2.5mm DFN/LCC4 CTX839CT-ND (Element 14 1842056) to try.

Tubular · 2014-03-05 03:22

Hi Ray

Its a Fox924 tcxo module, 10MHz (using PLL8x). SIze is 5x3.2mm.

You're right about the pinouts, you could make it fit in a DIP8 eeprom socket and share i2c (for one prop to boot another). You'd have to do something to make pin 3 (reset) edge triggered so the ground on pin 3 (normally an address pin) wouldn't hold it in reset.

Cluso99 · 2014-03-05 14:03

Tubular wrote: »

Hi Ray

Its a Fox924 tcxo module, 10MHz (using PLL8x). SIze is 5x3.2mm.

You're right about the pinouts, you could make it fit in a DIP8 eeprom socket and share i2c (for one prop to boot another). You'd have to do something to make pin 3 (reset) edge triggered so the ground on pin 3 (normally an address pin) wouldn't hold it in reset.

I was thinking more along the lines that you would only connect pins 4, 5, 6 & 8 (ie cut the others on the underside).

Pins 4..1 make a nice propplug connection (on the top) and you have TV OUT (or a prop output pin with a series resistor).

Tubular · 2014-03-05 15:47

Cluso99 wrote: »

I was thinking more along the lines that you would only connect pins 4, 5, 6 & 8 (ie cut the others on the underside).

Pins 4..1 make a nice propplug connection (on the top) and you have TV OUT (or a prop output pin with a series resistor).

Ok yes that would work, just use one of the grounds on the end for the permanent (non prop plug) power.

jmg · 2014-03-05 20:00

Tubular wrote: »

Its a Fox924 tcxo module, 10MHz (using PLL8x). SIze is 5x3.2mm.

Another Oscillator module is the SiLabs Si504,
Available at Digikey, but getting one it is a little like joining a secret society.

Their stock says 0, but that just means it is special order-entry, ie you have to enter a frequency to get a part code, which you then order.
They DO have them in stock !

Rather a strange way to sell something, and I only found out after I emailed a query.
Most would look, see Zero and move on...

Comes in 2.5x2, 3.2 x 2.5 and 4 x 3.2mm, not quite as tightly spec'd as FOX924, but you buy a default frequency as any 32 bit real, and that is what it power up at, and then sending any other 32 bit real. sets a new Osc value.

With this, you could order 5.00MHz or 6.00MHz or any other value up to 100MHz

Tubular · 2014-03-05 21:02

Ok looks interesting.

I did play with the Si570 a while back, on a dual prop board. They are nifty but you are right, I had to order through a ham operator group buy, from memory.

I did some more pcb layout as you suggested jmg, putting all the components onto one side of the board (ie vaguely manufacturable), and a "DIP18" worked about right. I've sent it off to oshpark so I don't waste any more time on it until making sure it fits together. Will post detail in a separate thread soon

jmg · 2014-03-05 22:55

Tubular wrote: »

I did play with the Si570 a while back, on a dual prop board. They are nifty but you are right, I had to order through a ham operator group buy, from memory.

I did get my Si504's from Digikey, the process was just a little unusual.

(oh and they miss-tagged 80MHz max as 100MHz, so I thought I was getting 100MHz, and when I asked for > 80MHz, it just looked at me. Turns out the SiLabs part code was actually 80MHz when I reversed the part ID.)

I think Digikey have the same price on all, so smartest to buy 100MHz / ±20ppm = best spec variant.
The Si570 I think is a higher spec again, and quote a bit more expensive.

Propeller 1 in an 8 pin DIP

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