Pitolino - a small data logging gadget

Hi, I could not resist the temptation to design something small and maybe useful :slight_smile:
Pitolino:

  1. v2 49.53x49.53mm, both sides smt parts 0805, etc.
  • 4 mounting holes for M2 (holes 2.2mm diam.)
  • Sanguino pin numbering (avr_developers variant)
  1. atmega1284p smt, 6pin programming header
  2. uSDcard socket with P_MOS SD_VCC switch and olimex-like card det.
  3. PCF8563T, low power RTC, 200nA current, with opt. alarm to PC7
  4. USB mini connector - as 5V power supp. only, optional
  5. MCP1700 3V3 low drop, 1.6uA v-reg
  6. battery holder - CR1216, 10y with above RTC
  7. serial header - with sparkfun-like pinout and opt. cap in DTR for reset
  8. all atmega pins put on headers - 1500mil header’s rows span fits
    the larger solderless breadboards (spans over 2 boards), headers with 0.1" pitch
    Any feedback welcomed… :slight_smile:
    p.

Two sided board? Where is the RTC that presumably the crystal and coin cell are for?

Should be fun to assemble. :)

RTC is on the bottom side - see the blue picture - placed near the battery and 32kHz resonator…
PS: the board is 49x42mm (!!) - not easy to pack all the stuff on the top side only when using 0805 :slight_smile:
PS1: that is the old_school design - tubes on the top of the chassis and caps, chokes, resistors on the bottom side :slight_smile:

Cool. It would be nice to see some mounting holes as well. I find them useful lately. Price for the PCB in the same range as the small bobuino?

Mounting holes - hmm, difficult with this breadboard concept, the board is quite small.. PCB price - itead will tell me :) (it fits in the cheapest range)..

It would be also nice to have provisions for another RTC chip, and I am thinking DS3231.

PCF8563T is $0.80 and 200nA, DS3231 is $8 and 800nA (but 2ppm - nice)..

I like it. Shouldn't the coin battery have an exposed pad for the negative terminal?

The exposed pad is there - on the top side - at least I can see it with gerbview…

batexppad.jpg

Nice one Pito.

Added 4 mounting holes, 49x48mm size now, and numbering scheme as per avr-developers. A lot of opened Qs. See the first message. p.

Good stuff but again, why the two sided design? Dual-sided SMD assembly is a pain as far as I know… I restrict my boards to through-hole components on one side and SMDs on the other. But that’s because I’m lazy and use stencils + a reflow oven to attach my SMDs to the PCB.

Also, I choose my board sizes to coincide with mounting holes inside Serpac or Hammond plastic enclosures. Just a thought.

My goal is to have the pcb small (max 49x49mm) such it fits to Itead lowest pricing. And also low power. No special enclosure in mind. Soldering - a few resistors, caps, choke, and diodes are ~0805 which is doable manually without a stencil, the chips are easy to solder, I think, too. So - a quick solution if somebody wants to log some data into a uSDcard at a remote location.. Maybe 2.7Volt VCC would be enough and you can use a 3.7V lion or something like that. I am also thinking to replace the 1284p with 328p as it seems to me the 1284p is an overkill here..

pito: I am also thinking to replace the 1284p with 328p as it seems to me the 1284p is an overkill here..

328p or 324p?

When working with a board like the Pitolino Shield pictured above, how do you go about connecting the pins of parts? Solder wires to the pins or some sort of J connector?

As a beginner, all of the solder boards I've worked with so far have connected rails/traces.

Thanks, Jake

@jraskell: - 164, 324, 644, 1284.. @BlueJakester: the pitolino template shield - that is a template only - so one can take the template (with header's ready pin layout, pcb size, hole positions) and draw his own board in the free Eagle CAD - ie. with sensors, signal conditioning (opamps), ADC, DAC, memories, additional sdcards sockets, or a CPLD or an FPGA, etc. etc. :) As an example there is a protoshield with 0.1" grid for DIL packages and through hole components. You can design your own proto shield with smt pads when required.. This project is for people who want to learn more than programming only..

Thanks. I'm still learning :)

itead will do the full 50mmx 50mm pito. You don't need to artificially limit yourself to 49 x 49. How about a schematic - I don't see a lot of the typical Rs & Cs on the layout, maybe they are just on the other side.

What does this mean: 1500mil header's spacing fits the breadboards.

breadboards are not 0.1" spacing like perfboard?

As an example - shield with 2 CPLDs, an accelerometer, an athm. pressure sensor, oscillator and a memory chip…
And some LEDs and signal connectors placed outside the stackable headers, so you can see them when more modules sandwitched…
:slight_smile:

@crossroads - 1500mils means the distance (span) between the two headers rows, which are 0.1" pitch :) - there are parts on the bottom - I will add the picture to the first post (I deleted it).. - both sides have got GND planes, for better grounding there are GND vias - 49x49mm vs 50x50mm - I've seen a discussion on Itead's forum on that topic - where they measure the 50x50 - in the middle of the dimension line, or on its outer side??..

What about the Questions for final routing ? (see the first topic). Any recommendation ? p.