Basic Stamp - MAX7219 and Digit Numbering

G McMurry

I am doing my first project using the MAX7219 8 digit 7-segment display driver. All is coming up OK except for one big problem. It seems that the MAX7219 calls the right hand digit in a group of 4 Digit #1 and every 4-digit 7-segment LED package I can find calls the left hand digit #1.

Is this really true? Are the manufacturers that far out of sync with each other?

I am sitting here with a new PCB I just finished that runs all the digits reversed. What do I change? Sotware? Display Board? The Driver Board?

This all seems pretty stupid to me.

Maybe I am missing something.

Greg

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G McMurry

Have you tried reversing the output.

The stamps can send MSB first or LSB first. I'm not sure this would help. I have never used the MAX7219.


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Chris Savage

Hello,

When using the MAX7219 the digits are numbered from right to left so that the farthest right digit is 1, and then going left, 2, 3, etc up to 8. Oddly, though the follow the order of the digits listed on the pinout, the datasheet numbers the digits from 0 through 7 rather than from 1 through 8 which you have to send the chip.

This isn’t the first Dallas/Maxim chip to throw me off with something like this when learning it…the DS1302 days of the week are numbered 1 through 7 instead of 0 through 6, so setting 0 causes things to get messed up with the day of the week. But I digress…I hope this helps some. Take care.

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Chris Savage

Parallax Engineering
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