So i'm fairly new to arduino still but i'm trying to build a G-Meter for my friends Supra and I need some help. I found this article http://www.instructables.com/id/Temperature-Displayed-on-4-Digit-7-segment-common/ and I was going to build off of it but i realized with this setup I don't think i'll have enough digital pins. There will be 3 7-segment digits per direction (acceleration, deceration, bank left and bank right) so 12 digits total, what would be the best way to multiplex the 7-segment displays with the shift registers while using as few pins as possible? I have the code working well and only taking readings from the accelerometer for all 3 axes (although i'm only using 2) i'd like to be able to map the readings from the accelerometer +32000/-32000 to 200 (2.00 G per direction) . Can someone please assist me in setting up all 12 displays while using as few pins as possible and have the code be simple as well? Any help is much appreciated. Even pointing me toward an article with a similar setup that i could heavily modify to work to my advantage would be wonderful.
Welcome! The easiest way is to serial displays like this one:
You can get several to work together. They way that tutorial does, there won't be enough arduino pins to run 3 displays.
Keep the 12 digits in an digitArray. To send them out:
digitalWrite (ssPin, LOW);
for (x=0; x<12; x=x+1){
SPI.transfer(fontArray[digitArray[x]]); // fontArray[ ] defines the bit to segment mapping, digitArray is your data to send out
}
digitalWrite(ssPin, HIGH); // outputs on this rising edge
Course, that's a lot of chips. Using two MAX7219 instead (which are functionally like 16 shift registers) will cut down on the hardware needed. Use common cathode displays (common anode can be made to work also, have to create a different fontArray).
Would it work to get an arduino mega 2560 and just increase the digitpins to 12 in the code and add shift registers?
Why? I've daisychained 45 shift registers and driven them from 3 pins with a '328P.
No need for a Mega.
Because that way I could use 4 shift registers rather than 12.
Actually no it'd only be one shift register.
Crossroads,
The OP has a multiplexed 4-digit-7-segment display, not 4 separate 7-segment displays that can be driven like in your circuit. OP needs to drive the select lines (4 of them) HIGH with Arduino pins and the segment lines LOW with shift register to light up one segment. Then do the same to sequentially light up all segments one at a time and repeat in fast loops. It gets too complicated for a beginner to make the effort to mod the code so both select lines and segment lines are controlled by shift registers. I would probably go with a MEGA so there are enough pins to drive select lines for each 4-digit-7-segment display. OP can tie all select lines of 4 displays together and mod the code but that takes some time to mod the code too.