SPI instead of SHIFTOUT - MAX7219

[Darrel Taylor]

With SSPM3:0 = 0011, it specifies the SSP clock comes from Timer2/2. But you haven't set-up Timer2.

Since the MAX7219 is a 10mhz device, you can run it at the highest speed available from the PIC.
SSPM3:0 = 0000 -- SPI master mode, clock = FOSC/4

And I think CKE should be 1.

In the Main loop, you need to wait for the SSP to finish sending the last byte, before putting a new one in the buffer.

main:
    toggle PORTB.0 ' to see if something is happening
    SSPBUF = "A" ' write to SSPBUF to start clock
    WHILE !SSPIF : WEND
    SSPIF = 0
goto main

Also the MAX7219 needs a Latch(Load) signal from the PIC, to latch the last 16-bit's into the device. Since you're only sending 1 byte, I guess you just haven't made it that far yet though.
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[Momboz]

With SSPM3:0 = 0011, it specifies the SSP clock comes from Timer2/2. But you haven't set-up Timer2.

Since the MAX7219 is a 10mhz device, you can run it at the highest speed available from the PIC.
SSPM3:0 = 0000 -- SPI master mode, clock = FOSC/4

Many thanks Darrel Taylor.

Yes, you are right that's a mistake I have made. I wanted to have SSPM3:0 = 0010, i.e. the lowest speed.

And I think CKE should be 1.

I am not that far, I will check this later on.

In the Main loop, you need to wait for the SSP to finish sending the last byte, before putting a new one in the buffer.

main:
    toggle PORTB.0 ' to see if something is happening
    SSPBUF = "A" ' write to SSPBUF to start clock
    WHILE !SSPIF : WEND
    SSPIF = 0
goto main

If I add this while end loop the PIC stops and never gets further. the PORTB.0 is not blinking any more (check with a scope connected to PORTB.0).

It seems I have a problem with the interrupt setting the SSPIF flag never gets set.

What I did in my code is:

INTCON = %11000000       ' Set the interrupts, i.e. enable GIE and PEIE
SSPIE = 1                       ' Enable SSPIE interrupt

Is there any mistake I have overlooked in my interrupts setting?

Also the MAX7219 needs a Latch(Load) signal from the PIC, to latch the last 16-bit's into the device. Since you're only sending 1 byte, I guess you just haven't made it that far yet though.
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Yes, you are right, I am not that far in the programming. I am adopting rather a pragmatic approach, i.e. doing things step by step.

Thanks a lot.

[Darrel Taylor]

What I did in my code is:

INTCON = %11000000       ' Set the interrupts, i.e. enable GIE and PEIE
SSPIE = 1                       ' Enable SSPIE interrupt

Is there any mistake I have overlooked in my interrupts setting?

NO! You don't want to do that.

You just use the flag to tell when the SSP is finished.
If you enable interrupts without any interrupt Handlers, it goes off into never never land, overflows Stacks and generally just doesn't work.
<br>

[Momboz]

NO! You don't want to do that.

You just use the flag to tell when the SSP is finished.
If you enable interrupts without any interrupt Handlers, it goes off into never never land, overflows Stacks and generally just doesn't work.
<br>

Sorry DT

I wasn't complete in my previous answer.

The first thing I did was to test with the addition of the while loop as you proposed and it wasn't successful, i.e. No toggle on PORTB.0 signal. It looks like the While loop is blocking the process (or like SSPIF is never set). if I suppress the while loop the PORTB.0 will toggle again.

That's the reason why I thought about setting the interrupts.

[falingtrea]

Here is some sample code from meLabs. Maybe that would be of help to you.

http://www.melabs.com/resources/samples/pbp/spimast.bas
http://www.melabs.com/resources/samp...p/spislave.bas

[Momboz]

Here is some sample code from meLabs. Maybe that would be of help to you.

http://www.melabs.com/resources/samples/pbp/spimast.bas
http://www.melabs.com/resources/samp...p/spislave.bas

@falingtrea

Many thanks for the advice. I have seen these examples and I couldn't succeed since I need a peer to talk to via the SPI. I am intending just to drive a MAX7219.

Vielen Dank nochmals.

[Darrel Taylor]

It looks like the While loop is blocking the process (or like SSPIF is never set). if I suppress the while loop the PORTB.0 will toggle again.

That's the reason why I thought about setting the interrupts.

Works fine here.
Ran your program (with the suggested changes) on an 877, and It sends data from the SSP and blinks the LED.

It's A VERY FAST blink. Not visible to the naked eye (or clothed ones).

Try putting a PAUSE 200 in the Main Loop.
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[Momboz]

Works fine here.
Ran your program (with the suggested changes) on an 877, and It sends data from the SSP and blinks the LED.

It's A VERY FAST blink. Not visible to the naked eye (or clothed ones).

Try putting a PAUSE 200 in the Main Loop.
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Dear DT

I would like, first, to thank you very very much for your support and then I wish to give you a feedback on how far I went with my SPI interface.

After some investigation I could find the reason of the problem I have making SPI running on my board. It is a hardware issue. It's the way I am using the Melabs PICPROTO-USB board. That doesn't mean that Melabs PICPROTO-USB board is faulty.

On that board you have the possibility to use the USB board in high speed. Therefore you need a capacitor C7 (0.470 µF) as shown in the documentation of that Melabs board (http://www.melabs.com/downloads/ppusbsch_06.pdf). This seems to prevent the SPI interface for running properly. I have taken the C7 away and everything went fine with SPI interface.

Maybe we will have a new Melabs board with a jumper that could leave this capacitor out when using the SPI interface

For the time being I have to make a choice for by Melabs board usage: either using USB high speed (and put the C7 capacitor) or using SPI (and take away the capacitor).

Once again many thanks for your help.

Best wishes / Momboz

[Darrel Taylor]

Good find Momboz!

I see you mentioned the PICPROTO-USB up in post #3.
But I never even looked at the schematic.

For the time being I have to make a choice for by Melabs board usage: either using USB high speed (and put the C7 capacitor) or using SPI (and take away the capacitor).

If you're using a PIC with USB, the SPI interface will be on different pins, so it shouldn't be a problem.
But you're right. meLabs should have put a jumper in there for the capacitor.

Cheers!