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Grogster

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Posted: 01:05am 17 Mar 2015

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Hi folks.

Trying to get a 595 LED display working on the SPI port on a 470.

Can't get it to show up ANYTHING other then all segments on: 8.8.8.8.

SetPin 1,DOUT

SPI OPEN 10000,2,8
D1=SPI(&B00000000) 'Digit 1
D2=SPI(&B00000000) 'Digit 2
D3=SPI(&B00000000) 'Digit 3
D4=SPI(&B00000000) 'Digit 4
Pulse 1,1 'Latch line
SPI CLOSE
Do:Loop

End

I've tried changing the format from 3 to 2, and no-go.
I have tried using hex format for the data in the SPI command, and no-go.

Can anyone help me understand what I am doing wrong?

Schematic of LED display(PDF)

SDI is connected to SPI OUT on the 470
SDO is unconnected
CLK is connected to SPI CLOCK
LCK is connected to pin1 on the 470(latch line)

EDIT: Was using the wrong pin for SPI out, is now on pin8 of the 470.
Clock is still pin50. Latch is still pin1.

I am now getting stuff on the display, but it is not what is should be - just random segments, when with all zeros, it should be setting all segments OFF.Edited by Grogster 2015-03-18

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disco4now

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Posted: 02:58am 17 Mar 2015

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Hi Grogster,

Looking at Matherp's code when using the serial to parallel chips he sets latch=0 at initialisation and then sets latch=1 followed by latch=0 to clock it through there after. Does is need a Pin(1)=0 right at the start before PIN 1 is set to DOUT.

Regards
Gerry

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MM_Wombat
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Posted: 02:59am 17 Mar 2015

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From what I can see from the Schematic, Pins 8 & 13 need to be connected to gnd, and pins 10 & 16 need to be connected to vdd

try that and see how you go..

AussieWombat

Keep plugging away, it is fun learning
But can be expensive (if you keep blowing things up).

Maximite, ColourMaximite, MM+

Grogster

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Posted: 01:39am 18 Mar 2015

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PROGRESS!!!!!

Perserverence seems to be yeilding results.

Two mistakes I was making:

1) Forgot to connect the LED display GND to the Micromite GND, as I was using a different supply for the LED display due to it's current consumption

2) You need to leave the SPI port OPEN once you are finished. If you close the port, the display goes all "Flickery" - probably as SPI CLOSE returns the pins to a non-configured(read: high impedance) state.

Code that is working is:

SetPin 2,DOUT:Pin(2)=0

SPI OPEN 1000000,3,32
D=SPI(&B10000000100000001000000010000000)
Pulse 2,1 'Latch line
Do:Loop

This code lights all the decimal-point LED's.

Replacing with all zeros for the SPI command turns all the segments off.

This is how it should be.

Progress!

EDIT: Lots of progress.......

Enough for tonight.

1:17AM here - time to rest the little grey cells....

EDIT: You CAN close the SPI, but you have to latch the display first, THEN close the SPI port. Makes sense, when I think about it, but it is late, so my brain is on low RPM...

Nighty night. Edited by Grogster 2015-03-19

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Grogster

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Posted: 10:06pm 18 Mar 2015

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All up and running. Here is the sub that I wrote to take a standard textual input, convert that to numbers, and lookup a simple array to decode the bitmap for the segments etc.

SetPin 2,dout:Pin(2)=0 'Configure display latch pin

'=========================================
'SETUP SIMPLE ARRAY TO STORE DIGIT BITMAPS
'=========================================
Dim INTEGER DIGIT(10)
DIGIT(0)=&B00111111:DIGIT(1)=&B00000110:DIGIT(2)=&B01011011
DIGIT(3)=&B01001111:DIGIT(4)=&B01100110:DIGIT(5)=&B01101101
DIGIT(6)=&B01111101:DIGIT(7)=&B00000111:DIGIT(8)=&B01111111
DIGIT(9)=&B01101111

'=================
'MAIN CODE HERE...
'=================

'Demo code - can be removed.
Do
Input "Number to display "; N$
Input "Decimal Position "; DP
LED (N$,DP)
Loop

End

'============================================
'SUBROUTINE TO SHOW NUMBERS ON THE LED MODULE
'============================================
Sub LED (N$,DP)
If Mid$(N$,1,1)="_" Then 'Detect blank request for this digit
D1=0
Else
D1=DIGIT(Val(Mid$(N$,1,1)))
EndIf
If Mid$(N$,2,1)="_" Then
D2=0
Else
D2=DIGIT(Val(Mid$(N$,2,1)))
EndIf
If Mid$(N$,3,1)="_" Then
D3=0
Else
D3=DIGIT(Val(Mid$(N$,3,1)))
EndIf
If Mid$(N$,4,1)="_" Then
D4=0
Else
D4=DIGIT(Val(Mid$(N$,4,1)))
EndIf
If DP=1 Then D1=D1+128 'Specify location of decimal point(0 for none)
If DP=2 Then D2=D2+128
If DP=3 Then D3=D3+128
If DP=4 Then D4=D4+128
SPI open 100000,3,8
D=SPI(D4)
D=SPI(D3)
D=SPI(D2)
D=SPI(D1)
Pulse 2,1 'Clock the latch to make the display visable
SPI CLOSE
End Sub

This is working very well.

You can send a _ character if you want a blank digit.
You specify the location of the decimal point with a number from 1 to 4.

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Herry

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Posted: 08:27am 19 Mar 2016

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OK. Of the 4 wires from the neatly bezelled display, 1 goes to ground and 1 to 5 v, one (which one?) goes to 2 on the Micromite (I'm using 28 pin). Does the other one go to pin 3 (SPI out)? What about pin 25 (SPI clock)?

Hoping my questions aren't so na�ve that I'm getting no response!Edited by Herry 2016-03-22

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Grogster

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Posted: 01:11am 21 Mar 2016

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chronic PM'ed me to let me know the link to the schematic is broken.
Thanks, chronic

Here is a new link.

I looked for the old file, but I must have moved it.
Sorry if anyone else was looking for the image - the new link should show it for you.

@ Herry - I don't have any of those displays handy right at the moment, but going from the schematic, you put Vcc(supply) onto 5v supply(3v3 also works with a little less brightness), GND(ground) to ground, CLK(Clock) to SPI CLOCK, SDI(Serial Data In) to SPI OUT(MOSI), and LCK(Lock/Latch) to any spare I/O pin.

As per the code above, you use the SPI port to clock the data to the module, then once that is done, you clock(pulse) the LCK line once to make the display show the data you just clocked into it.

...you may have worked all this out by now yourself...(it took me a day or so to see your post)

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Herry

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Posted: 11:19pm 24 Mar 2016

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One thing I can't make out from the code is what is D (near the end)? It does not appear anywhere else!

Also, your list of connections make up 5 but there are 6 pins. Where should SDO be connected to?

I assume that the 'any spare pin' you have made pin 2 in your code. For me pin 2 is already in use and the spare will be pin 24. I assume I alter the setpin line and the Pulse line accordingly.Edited by Herry 2016-03-26

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Grogster

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Posted: 11:58pm 24 Mar 2016

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D is just a dummy variable to satify the SPI command.
D for 'Dummy variable'.

It can be anything, but ideally not any of your other variables.

EDIT: From the manual, Appendix D - SPI Commands:

Quote
When the SPI channel is open data can be sent and received using the SPI or SPI2 function. The syntax is:

received_data = SPI(data_to_send)

Note that a single SPI transaction will send data while simultaneously receiving data from the slave.

�data_to_send� is the data to send and the function will return the data received during the transaction. If you do not want to send any data (ie, you wish to receive only) any number (eg, zero) can be used for the data to send. Similarly if you do not want to use the data received it can be assigned to a variable and ignored.

SDO is 'Serial Data Out', which is the line you would connect to a 2nd display module's SDI pin, if you wanted multiple displays in a daisy-chain arrangement.

If you only have the one display, you simply leave SDO unconnected.

On the pulse, you are correct.
Adjust so that it reads Pulse 24,1
Don't forget to make pin24 an output at the top of the code....Edited by Grogster 2016-03-26

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Herry

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Posted: 12:02am 25 Mar 2016

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Got it! Just as I expected (except for SDO which I should have guessed!) Thanks a heap! Or, as we used to say in the UK -- in a richly plummy voice -- 'You are a scholar and a gentleman!'

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Grogster

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Posted: 12:04am 25 Mar 2016

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Anytime.

Smoke makes things work. When the smoke gets out, it stops!

Herry

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Posted: 01:32pm 19 Apr 2016

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Have been able to come off big work writing project and spent yesterday with the 595 and MM. Got it working. The only thing is, apart from the three digits I do want to display, I am getting odd segments illuminated before and after. I think I can nut this out but someone may be able to enlighten me and save time!

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Grogster

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Posted: 02:54pm 19 Apr 2016

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What speed are you running the SPI at?
Slow it right down to minimum for a start, and see if you still have the same issue.
If the issue is gone, you might just have been running the SPI too fast. The connecting cable to the display and the length of that cable starts to become more critical the faster you try to run the bus, so slow it down just for the purposes of testing.

If you are still getting odd segments where they should not be even at a slow SPI speed, then there is something wrong with the bitmaps for the digits. Double check the binary codes being sent for digits if you are using my example code, as all it takes is a zero or one in the wrong place, and you won't get what you expect on the display.

Good luck, and keep us posted - I will help where I can, and others will probably chime in with other ideas if the above does not help.Edited by Grogster 2016-04-21

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Herry

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Posted: 10:00am 23 Apr 2016

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Sorted. It was necessary to blank the digit I didn't need (the max I need is 3). Here's my take:

'Display module
SUB DISPLAY595(NUM$)' this routine is set for 3 digits
IF LEN(NUM$)=3 THEN
D1 = BIDIG(VAL(LEFT$(NUM$,1)))
D2 = BIDIG(VAL(MID$(NUM$,2,1)))
D3 = BIDIG(VAL(MID$(NUM$,3,1)))
D4=0
ELSEIF LEN(NUM$)=2 THEN
D1=0
D2 = BIDIG(VAL(LEFT$(NUM$,1)))
D3 = BIDIG(VAL(MID$(NUM$,2,1)))
D4=0
ELSEIF LEN(NUM$)=1 THEN
D1=0
D2=0
D3 = BIDIG(VAL(NUM$))
D4=0
ENDIF
SPI OPEN 100000,3,8
D=SPI(D4)
D=SPI(D3)
D=SPI(D2)' D is a dummy variable
D=SPI(D1)
pulse 24,1' clock latch using 'spare'
SPI CLOSE
END SUB

Senior?! �Whatever it says, I'm a complete and utter beginner...

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