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DigitalRedline
01-21-2010, 01:49 PM
Hey guys,

I'm trying to program a max 6969 16 output LED driver to use for a digital tachometer project. I obtained two max 6969's from maxim as free component samples. After reading the manual, I am still confused as how to write the proper code. I'm fairly sure that I wired the chip properly. Here's a copy of my code as is, could someone please check it for accuracy? Or does someone understand how the chip works? Additionally, I received two max 7219's (which are rather highly documented) that I also don't fully understand how to use. BTW I am programming on a BS2SX.




' {$STAMP BS2sx}
' {$PBASIC 2.5}

DIN CON 15
Clk CON 14
LE CON 13
OE CON 12

index VAR NIB
value VAR WORD
idx VAR NIB
counts VAR NIB

one CON %1111111111111110
two CON %1111111111111100
three CON %1111111111111000
four CON %1111111111110000
five CON %1111111111100000
six CON %1111111111000000
seven CON %1111111110000000
eight CON %1111111100000000
nine CON %1111111000000000
ten CON %1111110000000000
eleven CON %1111100000000000
twelve CON %1111000000000000
thirteen CON %1110000000000000
fourteen CON %1100000000000000
fifteen CON %1000000000000000
sixteen CON %0000000000000000

main:
'LOW OE
FOR counts = 0 TO 7
DEBUG DEC counts, CR, DEC idx, CR
LOW LE
PAUSE 1000
HIGH LE
PAUSE 500
LOOKUP idx, [one,two,three,four,five,six,seven,eight], value
idx=idx+1
SHIFTOUT DIN,CLK,MSBFIRST,[value]
'DEBUG DEC value, CR
LOW LE
PAUSE 1000
IF counts = 7 THEN GOTO restart
NEXT

restart:
idx=0
counts=0
GOTO main




Thanks!

RJM5
01-21-2010, 03:20 PM
Dear DigitalTachometer, I have been asking the same question. My suggestion is that you hire someone older and wiser (perhaps your dad) and that you pay him extremely well, and perhaps he can help you find a solution to this trying problem. RJM5

Franklin
01-22-2010, 12:20 PM
Can you get the chips to do anything? What happens when you run your code? I see nothing wrong with your code but I don't have anything to run it against so I am relying on you to tell me what is going on. What part of the datasheet do you not understand. There are so many questions.

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- Stephen

LEDboy
01-22-2010, 01:22 PM
DigitalRedline,

Look at the changes I made This should get you started I'm at work so I cant test this out but let me know what happens.

I updated the code I realized while driving home I goofed on it...this should work...let me know what it does.



'·{$STAMP·BS2sx}
'·{$PBASIC·2.5}

DIN·CON·15
Clk·CON·14
LE·CON·13
OE·CON·12

idx·VAR·NIB
value·VAR·WORD
idx·VAR NIB
counts·VAR·NIB

one······ CON·· %1111111111111110
two······ CON·· %1111111111111100
three···· CON·· %1111111111111000
four······ CON·· %1111111111110000
five······· CON·· %1111111111100000
six········ CON·· %1111111111000000
seven···· CON ·%1111111110000000
eight····· CON· %1111111100000000
nine······ CON· %1111111000000000
ten······· CON· %1111110000000000
eleven· · CON· %1111100000000000
twelve··· CON· %1111000000000000
thirteen· ·CON ·%1110000000000000
fourteen· CON ·%1100000000000000
fifteen··· CON· %1000000000000000
sixteen·· CON· %0000000000000000

main:
LOW OE· or just ground the pin on the IC I would just ground the pin
FOR·idx =·0·TO·7·········································· ·································
DEBUG·DEC·counts,·CR,·DEC·index,·CR
HIGH·LE··········································· ·············································'This allows the chip to receive data
PAUSE·50
LOOKUP·idx,·[one,two,three,four,five,six,seven,eight],·value
idx= index + 1
SHIFTOUT·DIN,CLK,MSBFIRST,[value\16]·········································· 'This shifts out data ALL 16 bits THE DEFAULT for the BS2 is only 8 bits
'DEBUG·DEC·value,·CR
LOW·LE············································ ···········································'This latches the data into the outputs of the·chip·and lights the LEDs
PAUSE·1000 CHANGE pause 1000 to PAUSE 50
idx= idx + 1················································· ······························· 'This will move from "one to two to three·and so on"
IF·counts·=·7·THEN·GOTO·restart
NEXT

restart:
idx=0
counts=0
GOTO·main

Post Edited (LEDboy) : 1/23/2010 1:49:23 AM GMT

DigitalRedline
01-24-2010, 01:11 AM
"I recently obtained two of your MAX 6969 16 port LED drivers to
| use for a digital tachometer. I am programming on a Parallax
| BASIC stamp and have a few questions regarding proper
| interfacing. First off: when do I send the Load Enable pulse?
| Do I set it high, shift out the data MSBfirst, then set LE Low?
| Or is it LOW, SHIFT, HIGH? Next, I have tied OE to ground via a
| 10K resistor as I read that this sets it low (as to not interfere
| with the normal operation of the chip. Is this a good idea?
| Lastly, Can I send my data as a 16 bit binary number with 0
| corresponding to an LED on and 1 corresponding with an LED off?
| I tried this and it seemed that the LED's all turned on
| irregardless of my numbers. I would expect a string such as
| %1111111111111100 to turn on LED's on port 0 and 1, but that
| didn't happen."

I submitted that email to customer service and they sent me this reply:

| When the LE is HIGH the LATCH is transparent, meaning any data on
| shift register is transfered to the LATCH. When LE is LOW the
| contents of the LATCH don't change (even if the shift register
| contents are changing, the output latch contents won't change).
|
| 1. "When do I sent the Load Enable pulse" : The LE enable pulse
| should be sent after the 16 bits are clocked in to the shift
| register. If you look at figure 2; the LE pulse is given after
| the 16 bits are clocked in at DIN. So you can give a LE low
| (while the 16 bits are being clocked in at DIN) then a LE pulse
| once the 16 bits are clocked in.
|
| 2. "OE tied to ground via a 10k resistor)" : The MAX6969 will
| follow the voltage at the OE pin to enable/disable the outputs.
| And if the voltage at OE is less than (0.3*V+) it will treat the
| OE as a LOW voltage (page 2). In typical applications the OE
| signal is generated by the micro-processor & are pulled LOW or
| HIGH. If you want to OE to be constantly be at GND; just tie it
| to GND directly.
|
| 3. Regarding your last question, you are right, a bit 0 will
| correspond to LED on and bit 1 will correspond to LED off.
|
| If all LED's are ON regardless of the numbers; that means the
| timing may not be right. The output latch is not getting the
| intended 16-bits you are clocking in.
|
| Regards,
| Maxim applications

I have tied the OE pin to ground via a 10K. LEDboy: Is there any way I can eliminate the pause 50 after HIGH LE and before the lookup table, because I originally intended the lookup table to serve as my pause. Also, I noticed that the MAXIM customer service rep mentioned something about the timing, is this why the pause 1000 should be changed to a pause 50?

Thanks!

DigitalRedline
01-24-2010, 02:35 AM
' {$STAMP BS2sx}
' {$PBASIC 2.5}

DIN CON 15
Clk CON 14
LE CON 13

LEd_Wait CON 1

DATA_VAR CON %1111111111111110

DO
HIGH LE
PAUSE LED_Wait
SHIFTOUT DIN, Clk, MSBFIRST, [DATA_VAR\16]
PAUSE LED_Wait
LOW LE
LOOP

There is a piece of test code. I am a bit confused by timing, and I don't seem to be able to turn just one LED on. It seems like a POV device, I just have to keep pulsing one LED to make it "appear" on, but from what I've seen from the manual, that shouldn't be the case. Eliminating the pauses (or making them like 5ms) seems to be the best solution so far.

Here is a revised copy of my original code:
' {$STAMP BS2sx}
' {$PBASIC 2.5}

'Test code for BS2sx running a MAX 6969 chip. Updated 1/23/10

DIN CON 15 'Data Input (Pin 2 on MAX 6969)
Clk CON 14 'Clock Input (Pin 3 on MAX 6969)
LE CON 13 'Latch Enable (Pin 4 on MAX 6969)

value VAR WORD '16 bit binary value for LED on/off state
idx VAR NIB 'Index variable (0-15), currently only 0-7 b/c I'm only using 8 LED's

'Data values for LED's turning on
one CON %1111111111111110
two CON %1111111111111100
three CON %1111111111111000
four CON %1111111111110000
five CON %1111111111100000
six CON %1111111111000000
seven CON %1111111110000000
eight CON %1111111100000000
nine CON %1111111000000000
ten CON %1111110000000000
eleven CON %1111100000000000
twelve CON %1111000000000000
thirteen CON %1110000000000000
fourteen CON %1100000000000000
fifteen CON %1000000000000000
sixteen CON %0000000000000000

main:
FOR idx = 0 TO 15 'have 8 repetitions
HIGH LE 'Latch enable high, accepts new data
PAUSE 1
LOOKUP idx, [one,two,three,four,five,six,seven,eight,nine,ten,e leven,twelve,thirteen,fourteen,fifteen,sixteen], value 'Lookup data based on the index variable in order to get the proper number of LED's to turn on
SHIFTOUT DIN,CLK,MSBFIRST,[value\16] 'Shift 16 bit data out MSBfirst
LOW LE 'Latch enable low, display data
PAUSE 1
idx=idx+1 'Go on to next number
IF idx = 15 THEN GOTO restart
NEXT

restart: 'used to go back to zero and start counting up again
idx=0
GOTO main

LEDboy
01-24-2010, 08:03 AM
' {$STAMP BS2sx}
' {$PBASIC 2.5}

DIN CON 15
Clk CON 14
LE CON 13


DATA_VAR CON %1111111111111110

Setup:
·HIGH LE

Main:

·DO
··
········ SHIFTOUT DIN, Clk, MSBFIRST, [DATA_VAR\16]
· PULSOUT LE, 5
· PAUSE 100

·LOOP
·END

sam_sam_sam
01-24-2010, 09:12 AM
I would like to try this chip as well here is my problem is this· I do not understand table 1

·It· dose· tell you what· (n) is
Table 1. 4-Wire Serial-Interface Truth Table
H R1 R2 … Rn-2 Rn-1······ What is Rn - #
L L R1 R2 … Rn-2 Rn-1
X R0 R1 R2 … Rn-1 Rn
X X X … X X H R0 R1 R2 — Rn-1 Rn
— — P1 P2 P3 … Pn-1 Pn L P0 P1 P2 … Pn-1 Pn L P0 P1 P2 … Pn-1 Pn····· What Pn- #

X X X … X X H Hi-Z Hi-Z Hi-Z … Hi-Z Hi-Z



L = Low-logic level.
H = High-logic level.
X = Don’t care.
P = Present state.
R = Previous state.

Hi-Z = High impedance.


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Sam

sam_sam_sam
01-24-2010, 09:20 AM
Here the second problem

I do not understand the part in red

4-Wire Serial Interface

The serial interface on the MAX6969

is a 4-wire serial interface using four inputs (DIN, CLK, LE, OE)<<I think you need to use all four for this to work

·and adata output (DOUT).

·This interface is used to write display data to the MAX6969.

The serial-interface data word length is 16 bits, D0–D15. See Figure 2.

The functions of the five interface pins are as follows. DIN is the serial-data input, and must be stable when itis sampled on the rising edge of CLK. Data is shifted in, MSB first.

This means that data bit D15 is clocked in first, followed by 15 more data bits finishing with the LSB, D0.

CLK is the serial-clock input, which shifts data at DIN into the MAX6969 16-bit shift register on its rising edge.
LE is the latch load input of the MAX6969 that transfers data from the MAX6969 16-bit shift register to its 16-bit latch when LE is high (transparent latch), an
d latches the data on the falling edge of LE (Figure 2).
The fourth input provides output-enable control of the output drivers.
If I understand this part right you have use this in your code but sure how to write·the code
OE is high to force outputs OUT0–OUT15 high impedance, without altering the contents of the output latches, and low to enable outputsOUT0–OUT15 to follow the state of the output latches.
OE is independent of the operation of the serial interface.
Data can be shifted into the serial-interface shift register and latched, regardless of the state of OE.
DOUT is the serial-data output, which shifts data out from the MAX6969’s 16-bit shift register on the rising edge of CLK.
·Data at DIN is propagated through the shift register and appears at DOUT 16 clock cycles later.
Can some one explane how to read and understand the

Figure 2. 4-Wire Serial-Interface Timing Diagram

What dose··t_-_-_-·mean it term of how to the write the code to make it work

Figure 3. LE and CLK to OUT_ Timing

tLRF

tLRR

tCRF

tCRR


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Sam

Post Edited (sam_sam_sam) : 1/24/2010 3:01:25 AM GMT

LEDboy
01-24-2010, 10:23 AM
Ok Redline and Sam I just ordered a few samples of the chip as soon as they get here I should be able to help you two out a little bit better than I am now.





Sam,

You only need to use DIN,CLK,LE...you can tie OE stright to ground.· You only need to use OE is if you plan on using the DOUT pin

As far as Table 1.· 4-Wire Serial_Interface Truth Table

When DIN is "H" than CLK rises and D0 goes "H" and D1 = R1 (Previous state) so with that said...

When DIN goes High then CLK rises and the shift-Regs contents of D0·goes HIGH and D1 - D15 stay in their previous states While LE is High the Latch Contents of D0 - D15 stay in their previous states.



When DIN goes Low then CLK rises and the shift-Regs contents of D0 goes Low and D1 - D15·change to the present state (you turned them on)·while LE is Low the Latch Contents D0 - D15 are updated to the prestent state you made them and OE is Low so whatever LEDs you wanted turned on should be on... Why this happens is because you set LE LOW and latched the data you supplied into the shift registers

tLRR stands for LE Rising to OUT_ Rising Delay....if you look at page three you can see what the symbols mean.

tLRF stands for LE Rising to OUT_ Falling Delay

tCRF stands for CLK Rising to OUT_ Falling Delay

tCRR stands for CLK Rising to OUT_ Rising Delay....You only need to worry about Figure 3 if you are going to use the DOUT Pin.

Post Edited (LEDboy) : 1/24/2010 4:20:22 AM GMT

sam_sam_sam
01-24-2010, 11:25 PM
I order a few samples to try this out my self and let you know how it work out

LEDboy

Thank you for explaining those item to me that help alot

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Sam

DigitalRedline
01-25-2010, 08:43 AM
Thanks!

So far I havn't been able to fully turn any one LED off. I'm also using the pulsout command (as reccomended by LEDboy). It seems that the LED's that are supposed to be off just flicker, while the ones that are on are solid. It also appears that they "ripple" from outputs 0-15. I thought that the data was shifted out MSB first, so the binary %1111111111111110 would just light the led on d0, but that doesn't appear to be the case.

Oper8r Al
01-25-2010, 09:50 AM
I think in your code in the first line after your do statement you are setting the LE HIGH and you should be setting it to low to accept the data into the shift register and then pulse the LE to send it to the outputs.

Try this and see if it works:

' {$STAMP BS2sx}
' {$PBASIC 2.5}

DIN CON 15
Clk CON 14
LE CON 13

DATA_VAR CON %1111111111111110

Setup:
LOW LE

Main:

DO

SHIFTOUT DIN, Clk, MSBFIRST, [DATA_VAR\16]
PULSOUT LE, 5
PAUSE 100

LOOP
END



DigitalRedline said...

' {$STAMP BS2sx}
' {$PBASIC 2.5}

DIN CON 15
Clk CON 14
LE CON 13

LED_Wait CON 50

DATA_VAR CON %1111111111111110

DO
HIGH LE
PAUSE LED_Wait
SHIFTOUT DIN, Clk, MSBFIRST, [DATA_VAR\16]
PAUSE LED_Wait
LOW LE
LOOP

LEDboy
01-26-2010, 05:33 AM
Hey I got my samples and I but a code up...its under "Working Code for the MAX6969







Redline,

·· Take out the DO.....LOOP statement.· That will help with the flickering....Theres no need to put it in a loop.....all its doing is updating the data with the same data it already has.




Post Edited (LEDboy) : 1/29/2010 5:37:08 AM GMT

pingapple
10-19-2013, 09:44 AM
I have problem using MAX6969 and tried to find help from the internet. This is one of the two forum pages I read. Now, my problem is solved. I would like to put down my findings to share with any one might need help.

0.1uF power line filter cap is essential. Without it, the IC does not perform correctly.
Tried to use mechanical switch & RC de-bouncing circuit to give clock signal to the IC. But the IC is very sensitive to noise on the clock signal. Use PIC16F690 to control the IC is all right so long as there is 0.1uF power filter cap.
A HIGH on DIN turns on an LED.
When LE is high, LED changes whenever DIN data changes. In the 6969 datasheet, it is described by the word, 'transparent'. We can turn LE to high any time we want.
When LE is low, latch is disabled. LED display data last latched.
It is OK to tide ~OE to ground to keep LED output enabled all the time.
I put some remarks on the 6969 datasheet (https://docs.google.com/document/d/1Xn421aXo0LH1H9MaVR3eQzpoWumvxGbVyCoLVYq-acU/edit?usp=sharing). You may find them useful.