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Topic: Questions on making a minimal/custom Arduino circuit @ 3.3v/8Mhz? (Read 4970 times) previous topic - next topic

xl97

Hi Robert-


outside of some I/O pins for some basic smd leds......and some buttons input to make those leds do something..... I dont think any (but I'll have to review to be sure)  :)

your schematic looks similar to mine  (I'll post when I get to work)..

but mine is missing the cap on the SD socket.. and I didnt do anything with AREF yet.. just using a cap and tying to GND is ok?
(I dont need to tie that to any voltage reference point?  (ie: the 3.3v line at all?)



Lastly...  (caps).. still a bit confused on these..

from the schematic,...it looks like ALL the caps used are polarized ones??  (or am I reading the symbol wrong?.. I dont see any +/- on the cap symbols anywhere?)

I thought the CAPACITOR symbol that had two STRAIGHT lines.. meant a regular old cap.. and a CAPACTOR symbol that had  stiaght line and 1 rounded line.. was signifying a POLARIZED cap?

is this true? (or am I under the wrong impression?)


in this case.. then ALL caps used her should be polarized?


thanks!..


Oh and Robert.. the pcb design/layout is appreciated.. but when I show you the space and size (shape) of the PCB.. you'll probably just laugh at me!  lol

thanks again!

we'll post when I get to work..and open things up again.





oric_dan

#16
Nov 30, 2012, 08:39 pm Last Edit: Dec 01, 2012, 12:52 am by oric_dan(333) Reason: 1
Despite what the symbol is, caps less than 1 uF are typically unpolarized, and >= 1 uF
are typically polarized.

dhenry

Quote
what IS the minimal (but still somewhat stable/safe) components needed?


A minimum implementation would include just the chip itself.

A reasonable minimum implementation would have a decoupling cap, a crystal + two caps, or a decoupling network on the analog supply. And then more from there, based on your needs.

I have done many "chip-only" minimum implementations myself.

xl97

hi..
thanks for the reply..

this can not (should not) be a chip by itself project... IMHO.. 

I mean I need it to be small.. but I want it to work and be somewhat stable!  lol


Since it will be running @ 3.3v & INTERNAL 8Mhz clock...  I dont need the caps/crystal.......correct?

RESET pin broken out (for easier flashing/uploading)
DTR pin broken out (for easier flashing/uploading)

AREF pin (correctly set-up... I see in the schematic Crossroads posted.. he has the AREF pin connected to GND through a cap... but I do NOT need to connect to the 3.3v for a voltage refeence?  Just keep it INTENRAL reference at the 1.1v or whatever?)

and of course I want to ensure that I 'correctly' set-up the battery/power input..

since there will NOT be any voltage regulator (battery supply will be within the 3-3.7v range max).. but I want it to be stable..no ripples.

follow same principles or ceramic/polarized cap on the input power lines?



@ oric_dan(333)
Quote

Despite what the symbol is, caps less than 1 uF are typically unpolarized, and >= 1 uF
are typically polarized.


thanks!.. rules like this help a noob like me.

I am still wrestling with 'decoupling'.. and 'KNOWING' when to use a certain component or not (like when to use ceramic vs polarized..etc)

hopefully I can get to a more final version tonight/tomorrow.. and I'll post for review..

appreciate all the discussion guys!

thanks!  :)

CrossRoads

The little ceramic decoupling caps are not polarized.  Example:
http://www.digikey.com/product-detail/en/C0805C104K4RACTU/399-1167-1-ND/411442

Rule of thumb/general guidance: 0.1uF cap on every Vcc/Avcc pin on every part located as nearby as possible.

Aref - needs a 0.1uF cap to Gnd if you are using the internal references
See 2.2:
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

westfw

Quote
Lithium coin cells are usually 3.6 volts, not 3.0.

that's wrong.   You can find Li-ion coin cells with a "nominal" 3.6V or 3.7V, but the vast majority of non-rechargable Li coin cells are 3.0V  http://www.duracell.com/media/en-US/pdf/gtcl/Product_Data_Sheet/NA_DATASHEETS/CR2032_US.pdf

dhenry

Quote
this can not (should not) be a chip by itself project... IMHO.. 

I mean I need it to be small.. but I want it to work and be somewhat stable!  lol


The chip-only implement will work and will be very stable.


xl97

update: well..  i got things up and running with a minimal/breadboard Arduino using +3.3v @ 8MHz internal clock

to be clear order of things (for me) were:

1.) hook up my Arduino Duemilanove 2009 board to USB
2.) Open IDE (I used v.23)
3.) Tools >>> Board >> (Duemilanove 2009)
4.) Tools >>> Serial Port  (select port your above Arduino is connected to)
5.) File >>> Examples >>> ArduinoISP..  (upload this sketch to your Arduino board.
6.) Disconnect.. from USB
7.) Connect a 100-120 ohm resistor between RESET & +5v (to disable auto-reset on the MAIN board)
8.) Connect your target board (minimal +3.3v/8Mhz internal clock) to the MAIN Arduino above.

Wiring Pnout:
Arduino board pin   >>>  Target board pin
               D10       >>>>           RESET
               D11       >>>>           D11
               D12       >>>>           D12
               D13       >>>>           D13
               GND      >>>>           GND
               +3.3v     >>>>           VIN on breadboard...

9.) Reconnect MAIN Arduino board to USB.
10.) Open IDE (I used v.23)
11.) Tools >>> Board >> (Breadboard 3.3v with Internal 8MHz clock)
12.) Tools >>> Serial Port  (select port your above Arduino is connected to)
13.) Tools >>> Burn Bootloader >> w/Arduino as ISP




(bootloaded and can upload sketches all day...)..

two things I noticed though...

1.) Does NOT work with Aruino IDE 1.0+ out of the box...not sure exactly how to make it work yet either.

From reading around, it seems to have something to do with:
a.) editing/adding pin_arduino.h or Arduino.h files to somewhere.
b.) edit the breadboard  'boards.txt' file.. and add a line at the end?

(not to sure.. a bit above my comfort level messign with boards.txt and stuff)



this is just specific to my project.. not about the minimal Arduino part..


----------------------------------------------------------------------------------------------------------------------------------------------------

2.) and the MAIN problem I need to overcome..   I cant seem to communicate/initialize an SD card???
Using an Arduino @ 16MHz (external crystal) & +5v... I have never had a problem.. with voltage divider or level shifter..or shield...

having the Arduino with +3.3v logic and INTENRAL 8MHz clock doesnt seem to work.. and I 'thought' I would be able to directly connect/communicate to it? (no voltage divider, no level shifter..etc)

been searching around.. and havent found much on using 3.3v8MHz internal clock -with- SD card..


anyone done this? (so I know Im not spinning my wheels?)

CrossRoads

Lets see the schematic you said you'd post back in #15 & #18, and your sketch.

How'd you bootload it?
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

xl97

(sorry thought I had posted it)..

I ran into this post while searching here on the topic.. and just updated the outcome..

I started a thread about 3.3v/8MHz Internal clock and SD card communication thread here:

http://arduino.cc/forum/index.php/topic,140732.msg1065311.html#msg1065311

I have that circuit mocked-up on a breadboard right now.. before I order PCBs and make it all SMD..

this is the SAME project.. that we discussed via PM.. (ultra tiny pcb with zero space to work with & custom pcb shape/outline)


CrossRoads

The last post in the other thread, you say  SD PIN        >>>     Arduino
DAT2(9)        >>>      NOT USED
CD/CS (1)      >>>     D10
CMD/DI(2)     >>>      D11
VSS1/GND(3)  >>>     GND rail
VDD/V++(4)    >>>     +3.3v rail
CLK/SCK(5)    >>>     D12
VSS2/GND(6)  >>>     GND rail
DAT0/DO(7)   >>>     D13
DAT1(        >>>     NOT USED

These are not the correct pins for SPI:
D13 - SCK
D12 - MISO
D11 - MOSI
D10 - SS

What is really connected?
Are you really running from coin cell? May not have enoughcurrent oomph for the SD card.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

xl97

(not sure if I should post here or there) hahah

hmm.. (Im hoping I just fat finger the pinout!)...

but I thought that was how I had it wired it up:

DAT2(9)        >>>      NOT USED
CD/CS (1)      >>>     D10
CMD/DI(2)     >>>      D11
VSS1/GND(3)  >>>     GND rail
VDD/V++(4)    >>>     +3.3v rail
CLK/SCK(5)    >>>     D12
VSS2/GND(6)  >>>     GND rail
DAT0/DO(7)   >>>     D13
DAT1(8)        >>>     NOT USED

I'll have to check when I get home...  looks like I have D12 and D13 switched??




lemming

This tutorial has some interesting tips on power saving a minimalist board.

http://www.sparkfun.com/tutorials/309

xl97

Well I checked it out.. looks like I only typed it wrong..

this is what I have:

DAT2(9)        >>>      NOT USED
CD/CS (1)      >>>     D10
CMD/DI(2)     >>>      D11
VSS1/GND(3)  >>>     GND rail
VDD/V++(4)    >>>     +3.3v rail
CLK/SCK(5)    >>>     D13
VSS2/GND(6)  >>>     GND rail
DAT0/DO(7)   >>>     D12
DAT1(8 )       >>>     NOT USED


so.. whilke I had typed it with D12 and D13 switched.. checking the wiring.. it was NOT as originally posted..

the above is how it 'is' currently wired.



I can upload any sketch.. but anything that uses the SD card 'fails'..


SD lib >>>  Files Sketch:  

Initializing SD card...initialization failed!



SdFat lib >>> SdInfo:

SdFat version: 20110902

type any character to start

card.init failed
SD errorCode: 0X1
SD errorData: 0X0

type any character to start



Im not sure where to start troubleshooting?


* Im not sure if this is/could be a boards.txt problem? (a tweak to a fuse setting because the timing is off or something 'odd'?
* Im not sure if I just need to add a cap/resistor somewhere that I missed? (everything is direct connect except for the cap on the VDD/VSS lines of the SD lines)
* Maybe not even possible to do this with 8MHz internal clock @ 3.3v?


Gotta be something silly Im doing on my end..??


heres the schematic:



thanks!

xl97

also to answer you Crossroads.

I am using a PSU..

but I have powered/tried it from being powered form the FTDi cable (+5v)..

I have tried from PSU @ +3.3v...

I have 'not' tired the coin cell that I plan on using in the end..(yet).. no point in trying it yet..lol


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