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Forum Index : Microcontroller and PC projects : MicroMite CFunction SPIPort behaving oddly

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CaptainBoing

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Joined: 07/09/2016
Location: United Kingdom
Posts: 1236
Posted: 11:05am 20 May 2020
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Morning Forum.

On a MicroMite Mk2 28 pin 170, has anyone had any joy getting the SPIPort routine in the Embedded routines in the firmware pack working? (can't use the normal SPI port).

I have something very odd happening whereby I am getting  the CS pin oscillating even when I have stopped the program and am at the > prompt.

Here is my sub to talk to the chip:

Sub MAX7221(MAX7221Dat As Integer)
Local Integer j
Pin(CS)=0 'CS Lo
j=SPIPort(2,DAT,CLK,MAX7221Dat,0,0,16)' 16 bits sent at 1MHz+
Pin(CS)=1 'CS Hi
End Sub

If I REM the line starting j= then I see the toggle from the CS pin, but if I un-REM it, I get the oscillation, even when my prog is not running. It starts up, makes a single call to the above Sub then ENDs, but that CS pin keeps waggling... at the > prompt(!).


HWInit:
Pin(CS)=1:SetPin CS,DOUT,OC' pin 14 =CS
Pin(DAT)=0:SetPin DAT,DOUT,OC ' set tx pin low then set it as an output
Pin(CLK)=0:SetPin CLK,DOUT,OC ' set clk pin low then set it as an output
SetPin 2, DIN ' dummy input pin

InitMAX7221:
MAX7221(&H0F01)' display normal (not test)
End




I have noticed a disparity in the SPIPort PDF, the header for the Function shows:

CFunction SPIPort(integer, integer, integer, integer) integer

which suggests four arguments passed to it, but the example shows

rd = SPIPort( rx, tx, clk, data_to_send, speed, mode, bits )

which shows seven arguments.

I used the example in my code as you can see. I tried changing the CFunction definition to include seven integers passed in but no different.

Bit stuck, any help/pointers greatly appreciated.
 
Geoffg

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Joined: 06/06/2011
Location: Australia
Posts: 2679
Posted: 01:05pm 20 May 2020
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It very much looks something is repeatedly calling your sub.  The CS low time is about 250uS which is about correct if the line starting j= is commented out.

I did a lot of testing of that CFunction and it worked fine.

Geoff.
Geoff Graham - http://geoffg.net
 
CaptainBoing

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Joined: 07/09/2016
Location: United Kingdom
Posts: 1236
Posted: 02:12pm 20 May 2020
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I agree, but it is happening at the > prompt, which kind of points to some backdoor thing going on. Also, I call the routine once then end and it still continues.

I am up against the clock here and I am now etching a tiddly level shifter so I can use the hardware SPI. The MAX7221 needs a a min 3.5V to recognise a hi, so direct wired doesn't cut it. Thought I could be clever using some 5V tolerant pins with pull-ups and the SPIPort function, I have to get this out the door tonight  

One thing I didn't try was flashing the firmware, I tend to do that if I get weirdness (rarely)

Thanks for quick response

h
Edited 2020-05-21 00:19 by CaptainBoing
 
Geoffg

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Joined: 06/06/2011
Location: Australia
Posts: 2679
Posted: 12:45am 21 May 2020
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Do you have a tick timer going off every millisecond?  That will keep running at the command prompt.

Geoff
Geoff Graham - http://geoffg.net
 
CaptainBoing

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Location: United Kingdom
Posts: 1236
Posted: 08:17am 21 May 2020
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Morning Geoff

No, no timers at all running. It is a mystery and definitely associated with the CFunction - if I REM it out, the problem doesn't manifest. I was checking for shorts and all sorts but it just made no sense. Maybe the HEX got corrupted when I copied it across or something.

In the end I etched a tiny 3-channel level-shifter (2 resistors and a FET per channel, all SMD so postage stamp sized board) which I "dead-bugged" onto the PCB and cut the tracks with appropriate back-wiring so I could use the hardware SPI port - all working and with the customer for testing. Version 0.1  

A mystery which I will visit again, but I just ran out of time... as usual.

Thanks
 
led-bloon
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Joined: 21/12/2014
Location: Australia
Posts: 52
Posted: 09:40am 21 May 2020
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Try:
Remove the "OC" in -"Pin(CS)=1:SetPin CS,DOUT,OC"
and the rest of the pins for SPI2 as well.
led
 
CaptainBoing

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Location: United Kingdom
Posts: 1236
Posted: 12:57pm 21 May 2020
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Hi 'bloon

I will replicate things another time, the board is with the customer now.

It is a mystery but your idea is a good one to see if that low can be "driven" into. I will add it to the list.

I want to get this working as SPI on any pin is a really nice to have. Never used the embedded function before... have used the serial routines lots of times.

SPI (and serial) as protocols are about as simple as it gets - especially one way. I have bashed them in assembler a few times over the years.
 
JohnS
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Joined: 18/11/2011
Location: United Kingdom
Posts: 2040
Posted: 04:28pm 21 May 2020
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Could it be the CFunction (CSub) that is keeping the pin going?

(I'm guessing it can still be active even back at the command prompt.)

John
 
CaptainBoing

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Posts: 1236
Posted: 08:58pm 21 May 2020
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Evening John.

That was my guess too - it needs a power cycle to stop it i.e. once started I have no control (prolly a CPU RESTART would fix as well but dint try). It is not expected behaviour and from code that is quite old (= mature)... Geoff says it has been tested extensively and that is good enough for me.

I am wondering if I missed a bit off the HEX when I copied the routine from the PDF or something. I have had odd instances of weird stuff happening in the past that was fixed by re-flashing, but everything else about this uM is spot on - it doesn't have that "feel" of a corrupt firmware.

A proper mystery that I am keen to get my teeth into - I will build up a test rig when it gets a bit quieter (never been busier, got four projects going out of the workshop this week) but for now I modded the PCB to use the hardware SPI... all working and on test with the customer.

h
 
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