MAX7219 help
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Posts: 46,084
I am using the Max7219 for driving LED 7-seg displays quite
successfuly. I basically used (with very little modification) the
AppNote from Parallax.
However, my current application require using the chip to turn on 64
LED's in rapid sequence from LED 0 (the first) to LED 64. The
Max7219 data sheet is somewhat criptic and I dont' really understand
how to use the chip in non-BCD mode.
Can anyone suggest how I can code the BS2 to do this?
many thanks
Al
successfuly. I basically used (with very little modification) the
AppNote from Parallax.
However, my current application require using the chip to turn on 64
LED's in rapid sequence from LED 0 (the first) to LED 64. The
Max7219 data sheet is somewhat criptic and I dont' really understand
how to use the chip in non-BCD mode.
Can anyone suggest how I can code the BS2 to do this?
many thanks
Al
Comments
LED Matrix with a Maxim 7219 LED display driver. All the wiring seems to be
correct, but, I'm getting interference with the some of the LED on the
Matrix (ie Columns 1 & 4 are always on). Below is the section of code that
"drives" the Matrix. I attempted to create a couple of different test
behaviors, I created a character that turns all the LEDs on, to which the
LED Matrix only turns on rows 1 & 4, and columns 2, 3 & 5. The demo in the
article displays the letters B, S, and 2, you can see the letters appear
through the additional LEDs. Any ideas? I'm using a BOE rev d, with a BS2.
All help is appreciated.
MG
--- Code Segment Follows ---
FOR col = 1 TO 5 ' character is 5 columns wide
READ (eeAddr1 + col - 1),d7219 ' read column data from EEPROM
SHIFTOUT Dpin,Clock,MSBFirst,[noparse][[/noparse]col,d7219]
PULSOUT Load,3
NEXT
RETURN
wired up. Have you tested the display by hand to see if the pins do what
they should?
Original Message
> I'm attempting to impliment Nuts and Volts article #70 which drives a 5X7
> LED Matrix with a Maxim 7219 LED display driver. All the wiring seems to
be
> correct, but, I'm getting interference with the some of the LED on the
> Matrix (ie Columns 1 & 4 are always on). Below is the section of code
that
> "drives" the Matrix. I attempted to create a couple of different test
> behaviors, I created a character that turns all the LEDs on, to which the
> LED Matrix only turns on rows 1 & 4, and columns 2, 3 & 5. The demo in
the
> article displays the letters B, S, and 2, you can see the letters appear
> through the additional LEDs. Any ideas? I'm using a BOE rev d, with a
BS2.
Matrix match the pinouts in the article. I tested everything by hand and it
works fine. If it were a pinout problem I would expect a single light, or
maybe two to not cooperate, but two full lines? That would mean that
several Anode/Cathode lines are high.
Any other suggestions?
Any chance Mr. Jon Williams (article author) has any ideas?
Matt
Original Message
From: Rodent [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=9lQnOr7xXvOvpVBO47vIMRxdnYb8CNNA2syZBW_oI8SDncBh83FhUpnUcjU0x-s3JldAuq79hO_3XXnu]daweasel@s...[/url
Sent: Monday, August 05, 2002 6:07 PM
To: basicstamps@yahoogroups.com
Subject: Re: [noparse][[/noparse]basicstamps] MAX7219 Help
Sounds to me like the pinout on the display may not match what you have
wired up. Have you tested the display by hand to see if the pins do what
they should?
Original Message
> I'm attempting to impliment Nuts and Volts article #70 which drives a 5X7
> LED Matrix with a Maxim 7219 LED display driver. All the wiring seems to
be
> correct, but, I'm getting interference with the some of the LED on the
> Matrix (ie Columns 1 & 4 are always on). Below is the section of code
that
> "drives" the Matrix. I attempted to create a couple of different test
> behaviors, I created a character that turns all the LEDs on, to which the
> LED Matrix only turns on rows 1 & 4, and columns 2, 3 & 5. The demo in
the
> article displays the letters B, S, and 2, you can see the letters appear
> through the additional LEDs. Any ideas? I'm using a BOE rev d, with a
BS2.
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mgeorgy@d... writes:
> Any chance Mr. Jon Williams (article author) has any ideas?
>
There is the chance that I erred in transposing the schematic from my
breadboard to the column, but since its publication I haven't had any
complaints about it until now. I'm sure a quick look at the MAX7219 data
sheet and your setup would confirm my error or yours.
-- Jon Williams
PS: Okay, I'm 40 ... but I hate being called "Mr."
[noparse][[/noparse]Non-text portions of this message have been removed]
Of course your Alzheimer's may have kicked in -- that article was a few
years ago.
Remind me at the meeting to show you what I put together from that article.
Original Message
> > Any chance Mr. Jon Williams (article author) has any ideas?
> >
> There is the chance that I erred in transposing the schematic from my
> breadboard to the column, but since its publication I haven't had any
> complaints about it until now. I'm sure a quick look at the MAX7219 data
> sheet and your setup would confirm my error or yours.
>
> -- Jon Williams
>
> PS: Okay, I'm 40 ... but I hate being called "Mr."