Pages: 1 2 [3] 4   Go Down
Author Topic: Small 8x8 matrix driver?  (Read 5080 times)
0 Members and 1 Guest are viewing this topic.
Valencia, Spain
Offline Offline
Faraday Member
**
Karma: 144
Posts: 5336
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

$1.36 in the quantities he is talking about if this makes it to production.  Atmel prices their product pretty darn reasonable if you ask me.

Yep. The ATmega is probably cheaper then the MAX7219.

I bought a dozen ATtiny84s from Farnell las week for 94 cents each (Eurocents). They want 10 Euros for a single MAX7219.

Logged

No, I don't answer questions sent in private messages (but I do accept thank-you notes...)

0
Offline Offline
Newbie
*
Karma: 0
Posts: 37
:D
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Yep you really cant compare the two in terms of price. If/when I do finish the project, ill be sure to post the code so everyone else can take advantage of the cheaper driver.
Logged

Offline Offline
Edison Member
*
Karma: 116
Posts: 2205
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

The whole concept of buying max72xx now makes zero sense to me.

Those guys go out of the market for a (very good) reason.
Logged

0
Offline Offline
Newbie
*
Karma: 0
Posts: 37
:D
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

The whole concept of buying max72xx now makes zero sense to me.

Those guys go out of the market for a (very good) reason.

Well there is an advantage to it, especially in very large quantities, and thats the fact that you don't have to program an extra MCU. But yes, cost (and possibly even feature wise) the atmega is the clear way to go.
Logged

Global Moderator
Boston area, metrowest
Online Online
Brattain Member
*****
Karma: 524
Posts: 26422
Author of "Arduino for Teens". Available for Design & Build services. Now with Unlimited Eagle board sizes!
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

Not so clear - say your application called for DIPs instead of surface mount.
taydaelectronics.com has MAX7219 in DIP for $1.25.  I just bought 8, shipping was $1.80. Order also included 20 panel mount power jacks, 4 toggle switches, and a mess of resistors.

vs $2.78 (qty 25) for lowest priced 168 in DIP
http://www.mouser.com/ProductDetail/Atmel/ATmega168-20PU/?qs=sGAEpiMZZMtkfMPOFRTOl51o10QgrNfF
and $1.59 at digikey
http://www.digikey.com/product-detail/en/ATMEGA168A-PU/ATMEGA168A-PU-ND/2271215
both charge something like $6.95 for lowest priced shipping.
Logged

Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

0
Offline Offline
Newbie
*
Karma: 0
Posts: 37
:D
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Hmm...good point, though I don't know how reliable they would be in orders of 100. Then again, they might be great. It's too bad they didn't make one of the MAX72xx's in a smaller package...
Logged

Global Moderator
Boston area, metrowest
Online Online
Brattain Member
*****
Karma: 524
Posts: 26422
Author of "Arduino for Teens". Available for Design & Build services. Now with Unlimited Eagle board sizes!
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

It is available on 24-pin wide SO surface mount package - its just a little thicker than you wanted.

Or as bare die if you wanted it really thin.
Logged

Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

0
Offline Offline
Newbie
*
Karma: 0
Posts: 37
:D
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

It is available on 24-pin wide SO surface mount package - its just a little thicker than you wanted.

Or as bare die if you wanted it really thin.
A bare die would be great, though how would I go about soldering that (or having it soldered for me) in a cost effective and simple way?

Edit: I just did some googling, and it I think the bare die would be overkill for this little production run.
« Last Edit: October 13, 2012, 12:30:04 pm by Nadav Ami » Logged

Offline Offline
Edison Member
*
Karma: 116
Posts: 2205
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Quote
It's too bad they didn't make one of the MAX72xx's in a smaller package...

I wonder why that's the case, ...
Logged

Global Moderator
Boston area, metrowest
Online Online
Brattain Member
*****
Karma: 524
Posts: 26422
Author of "Arduino for Teens". Available for Design & Build services. Now with Unlimited Eagle board sizes!
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

Another advantage might be interface speed.
MAX7219/7221 can receive data at 10 MHz.  I use  mine at default SPI settings which I think is 4 MHz.
If your main processor was really tied up and you wanted to send stuff out at 8 MHz to get it out of the way quick. The master can do that, I think testing has has shown a 168/328 cannot receive that fast tho due to the slave having to sample (the CS pin?) or something along those lines.
Logged

Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

0
Offline Offline
Newbie
*
Karma: 0
Posts: 37
:D
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Another advantage might be interface speed.
MAX7219/7221 can receive data at 10 MHz.  I use  mine at default SPI settings which I think is 4 MHz.
If your main processor was really tied up and you wanted to send stuff out at 8 MHz to get it out of the way quick. The master can do that, I think testing has has shown a 168/328 cannot receive that fast tho due to the slave having to sample (the CS pin?) or something along those lines.
Yeah, ideally that would be the way to go. But size and cost are really the most limiting factor.
Logged

Offline Offline
Edison Member
*
Karma: 116
Posts: 2205
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Quote
a 168/328 cannot receive that fast tho due to the slave having to sample (the CS pin?)

True, when implemented poorly.
Logged

Global Moderator
Boston area, metrowest
Online Online
Brattain Member
*****
Karma: 524
Posts: 26422
Author of "Arduino for Teens". Available for Design & Build services. Now with Unlimited Eagle board sizes!
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

Quote
True, when implemented poorly."

False - max speed is a hardware function, not something  users have any implementation control over:

"In SPI Slave mode, the control logic will sample the incoming signal of the SCK pin. To ensure correct sampling of
the clock signal, the minimum low and high periods should be:
Low periods: Longer than 2 CPU clock cycles.
High periods: Longer than 2 CPU clock cycles."
Logged

Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

0
Offline Offline
Newbie
*
Karma: 0
Posts: 37
:D
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Still though, shouldn't 115200 baud serial be fast enough for this application?
Logged

Global Moderator
Boston area, metrowest
Online Online
Brattain Member
*****
Karma: 524
Posts: 26422
Author of "Arduino for Teens". Available for Design & Build services. Now with Unlimited Eagle board sizes!
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

Yes.  The above was only discussing reasons why the ATmega is not always the clear way to go.
In this case, your need for overall thinness, similar cost, and no need for ultimate in interface speed indicates the Atmega is the way to go, as long as your time to develop the max7219 function is not factored in.
Logged

Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

Pages: 1 2 [3] 4   Go Up
Jump to: