MAX 7219 daisy-chain
Hi there,
I am trying to daisy-chain the MAX 7219 LED-driver chip. As soon as I
connect more than 6 chips the results are unpredictable. There seem to be
some line-losses ...
Now I am trying to stabilize the LOAD and CLOCK signal by using a line
driver to create a potential first and each subsequent MAX 7219 chip would
get a line receiver.
The parts I am using are:
Quad line driver DS26LS31C (National Semiconductor)
Dual line receiver DS9639ACN (National Semiconductor)
Any comments on my approach or the specific parts I am using?
Thanks in advance,
erwin
I am trying to daisy-chain the MAX 7219 LED-driver chip. As soon as I
connect more than 6 chips the results are unpredictable. There seem to be
some line-losses ...
Now I am trying to stabilize the LOAD and CLOCK signal by using a line
driver to create a potential first and each subsequent MAX 7219 chip would
get a line receiver.
The parts I am using are:
Quad line driver DS26LS31C (National Semiconductor)
Dual line receiver DS9639ACN (National Semiconductor)
Any comments on my approach or the specific parts I am using?
Thanks in advance,
erwin
Comments
I am daisy-chaining several MAX 7219 LED-driver chips but I am not able to
drive more than 8 chips. Whenever I try to connect chip 9 it plays the
sequence of chip 9 on chip 1????
To get a better signal I use a differential line driver/receiver pair for
LOAD and CLOCK (parts; Nat.Semi. DS26LS31C/DS9639A).
Any ideas?
Are there any hardware or software tricks I am not aware of?
Thanx for your time,
erwin
addresses for 0 to 7 or 8 chips so 8 may be the limit! Registers d8
to d11 it also says you can daisy chain several 7219 together ( ok
somebody look up several and let me know how many this is). The data
sheet it at the Maxim web page and look up table 2 Register Address
Map.
erwin redl wrote:
>
> Hi there,
>
> I am daisy-chaining several MAX 7219 LED-driver chips but I am not able to
> drive more than 8 chips. Whenever I try to connect chip 9 it plays the
> sequence of chip 9 on chip 1????
>
> To get a better signal I use a differential line driver/receiver pair for
> LOAD and CLOCK (parts; Nat.Semi. DS26LS31C/DS9639A).
>
> Any ideas?
>
> Are there any hardware or software tricks I am not aware of?
>
> Thanx for your time,
>
> erwin
i managed to get chip 9 to work but now chip 10 is only randomly flashing ...
guess that's the proof that MAX 7219 can drive more than 8 chips - the
datasheet promises 16 chips in a daisy-chain ...
maybe i should also use a differential line driver/receiver pair for the
DATA bus?
any ideas?
erwin
Thanks for the reply, sorry I have left your original reply on
another PC, however, do you have a circuit diagram of the arrangement
you were using to seee if we are doing the samething ?
He is a reply from Parallax and a bit more of my own setup. Any feed
back would be welcome.
Cheers Chris
****************************************************************
Hi thank for your reply, however I think you may have mis understood
the data sheet ?
I'm using 16 x 7219 ic's i.e I driving 1024 seperate LED's
the 3 bit you refure to are local addressing of a digit if you use 7
segment displays, not actual MAX chips
Every thing in the data sheet has been implimented.
I have a mains filter powering a 10VAC 100VA transformer feeding 16 x
bridge rectifiers and 1000mf caps then feeding 16 x 5vdc 1 amp
Regulator to each MAX7219, all decoupled.
A single CLK and Load going to 16 x MAX's and Din to Dout through
out. Everything is Common GND on the logic and 5vdc side. Stared
every 4th board down to Earth/chasy.
Scoped everything and see nothing to cause data problems.
I'm sending 16bit Shiftouts x 16 then sending a Load Pulse of 100ns
What seem to be happening is that the chain of data, before it is
loaded, has picked up or lost a 0 or 1 and then causes the incorrect
data to be stored.
Seems to be susceptable to fluresents if not Earthed.
My display is 2.5m long
May be I have an Arial or the BS2 needs a line driver. ?
Any thoughts ?
Cheers Chris
Original Message
From: Andy Lindsay <alindsay@p...>
To: <Christopher_Hill@M...>
Sent: 12 June 2000 21:18
Subject: RE: MAX 7219 - Cascading
| - Table 2 on page 7 of Maxim's 7219/7221 data sheet shows the
addressing
| system used. It's got 4 bits, the fourth of which is used to set
modes.
| This leaves 3 bits for addressing one of eight chips. Might want
check
| again with Maxim on this infinite cascade thing.
|
| If I misunderstood the data sheet, please let me know, and I'll
take a
| closer look. Also, if infinite cascading really is possible, try
the
| following:
|
| - The voltage regulator powering these chips & displays needs to be
able to
| supply enough juice for everything. Monitoring the power supply
with a
| scope before and after a significant increase in drivers might be a
way to
| verify or rule out this problem. Pages 10 and 11 discuss power
supply
| ripple minimization and power dissipation calcs.
|
| - Check the signal (again on an O-scope) coming out of various
drivers (Dout
| to Din) in the series and look for signal degradation.
|
| Andy
|
| Andrew Lindsay, Applications Engineer
| Parallax, Inc. Technical Support
| E-Mail...........alindsay@p...
| Voice............(916) 624-8333 ext 113
|
| Parallax, Inc. home page....................www.parallaxinc.com
| BASIC Stamp Educational Resources...........www.stampsinclass.com
| SX Microcontroller University Resources.....www.sxtech.com
|
|
|
|
Original Message
| From: StampTech [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=jW3x53SqhtFPcOg4RieUmCXE8PBQZ2y5pJYFhKDuCPapLKjoZxAl8NhT6FImj18fK7X2NrkW5E7PEqJCkif4ai0]gduran@p...[/url
| Sent: Monday, June 12, 2000 7:22 AM
| To: alindsay@p...
| Subject: Fwd: MAX 7219 - Cascading
|
|
| Andy can you please take a few of these, Stephen will not be in
today he
| got too much Sun on his trip. He said he will be in on Tuesday, I
kinda got
| slammed with emails. Thank's
| >From: "Christopher Hill" <Christopher_Hill@M...>
| >To: <stamptech@p...>
| >Subject: MAX 7219 - Cascading
| >Date: Mon, 12 Jun 2000 08:39:14 +0100
| >X-Mailer: Microsoft Outlook Express 5.00.2314.1300
| >
| >Hi
| > >
| > >I'm having the same problem as a few people in the eGroup
Archieves, can
| > you help ?
| > >
| > >I have 16 MAX 7219 cascaded and have random data after about the
8th
| > max7219's
| > >
| > >Is there a reason for this and a solution ?
| > >
| > >My thoughts where,
| > >
| > >1. may be my data bus was to long and picking up noise
| > >2. Need more Decoupling at the BS2 to drive the paralleled CLK
and
| > >LOAD
| > >
| > >Require a solution urgently, any help would be appreaciated.
| > >
| > >P.s MAXIM tell me there should be no limit to the number of MAX
you
| > >can Casacade
| > >
| > >Cheers Chris
|
|
--- In basicstamps@egroups.com, erwin redl <parallel@t...> wrote:
> hi there,
>
> i managed to get chip 9 to work but now chip 10 is only randomly
flashing ...
>
> guess that's the proof that MAX 7219 can drive more than 8 chips -
the
> datasheet promises 16 chips in a daisy-chain ...
>
> maybe i should also use a differential line driver/receiver pair
for the
> DATA bus?
>
> any ideas?
>
> erwin