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Forum Index : Microcontroller and PC projects : CMM2: TassyJim's 40way IO Test Program, questions ?

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Womble

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Joined: 09/07/2020
Location: United Kingdom
Posts: 267
Posted: 12:05am 12 Aug 2020
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Following on from the saga of building my CMM2, I thought it would be a good idea to test the IO connecter.

  TassyJim said  Not a demo - more a test but I had to put it somewhere.
This tests the wiring of your 40 way connector.
It needs 28 resistors of the same value. I used 200 ohm but anything from 200 to 2k should do the job.

It first checks to see if the cable is the right way around.
Then we test all digital IN and digital OUT.
The analog in is tested by setting one digital OUT high and one LOW to give a voltage at VCC/2.

My fist go was on a breadboard then I got creative with the soldering iron.

Jim's Original Post

This inspired me to break out the "Stripboard" and test the 40way IO connector on my CMM2 v3 Kit.  Rummaging in my leftover components store I came up with twenty eight 1.2K 2% resistors and the other components required to build this tester.

I used this schematic:

Modified from Jim's original to include the recommended switch.

  TassyJim said  The pull-up used during boot to initiate a reset is not strong enough to handle the load my tester puts on it.
When the pin tester is plugged, it keeps pin 40 low during the boot sequence.

When you change some options such as keyboard, the system does a reboot and if my tester is plugged in, you loose all settings.

If that's a problem, you could put a switch on pin 40 and only close it during testing.


  TassyJim said  It SHOULD have a switch.
It is always good practice to plug things in while shut down and that is something I should have allowed for.


Jim's Program:
CMM2_40way_Test.zip

produced this output:



I assume this portion of the program produces the errors:

   PRINT
   PRINT "Testing Analog IN"
   ' testing analog in.
   ' set one pin high and one pin low to give VCC/2 at the common point.
   SETPIN 3, DOUT
   SETPIN 5, DOUT
   PIN(3) = 1
   PIN(5) = 0
   
   FOR n = 0 TO 11
     testpin = apins(n)
     SETPIN testpin, AIN
     v = PIN(testpin)
     IF V < 1.58 OR V > 1.7 THEN PRINT "Pin ";testpin ;" failed AIN - ";v : bug = bug+1
     SETPIN testpin, OFF
   NEXT n
   SETPIN 3, OFF
   SETPIN 5, OFF


I am getting an analog reading for V of around 1.34 - 1.35 (volts), which flags as an error.

Is this because I am uisng 1.2K resistors ?

As mentioned elsewhere on the forum I had some problems with my CMM2 build, so it may be that I have some poor solder joints, or have damaged my board with all the rework carried out during the troubleshooting.

I find it interesting that the errors only occur with the Analog Inputs, all 12 of them.  Makes me suspect my 40way IO connector  might be fine, and my resistors are too high a value.

Thoughts please, Thanks

Womble
Edited 2020-08-12 10:11 by Womble
 
Womble

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Joined: 09/07/2020
Location: United Kingdom
Posts: 267
Posted: 12:16am 12 Aug 2020
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I used 1.2K 2% resistors because I had them.
They were free, wombled from an electronics lab that was closing down and given to me by a friend.
 
bigmik

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Joined: 20/06/2011
Location: Australia
Posts: 2950
Posted: 01:46am 12 Aug 2020
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Hi Womble,

I reported similar to Jim when I started building CMM2 as all of them seemed to fail on at least one AIn by not much (ie mine were 1.57 and the test failed below 1.58) And I found that I worked around this by setting all of the IO as inputs (as opposed to OFF) and the Tests passed.

It is a little bit touch and go, as there are a lot of IO in parallel that can affect the level that is actually presented (via a resistor) from the one output pin.

Jim emailed me and said when he wrote the program it worked on his first board then failed similarly on subsequent boards. His fix was to adjust the Ain range to be between 1.55 and 1.75v

This is basically Jim's fix code however I see your results are around 1.34 so will probably still fail..

Just before the Analog tests you will see 4 lines I added to set unused pins to Din instead of OFF status.. remove the REMs and try with that..

There is definitely a difference between Din and OFF.

I used 220R for mine..

' CMM2 pin tester.
' requires a bank of 28 same size resistors (I used 200 ohm)
' connected from each pin in pintest() array to a common point

DIM pintest(27) = (3,5,7,11,13,15,19,21,23,27,29,31,33,35,37,8,10,12,16,18,22,24,26,28,32,36,38,40)
DIM apins(11) = (7,13,15,29,37,8,10,12,16,22,24,26)
DIM INTEGER k, bug
DIM FLOAT v

FOR k = 0 TO 27 ' make sure all pins are floating
  SETPIN(pintest(k)), OFF
NEXT k

CLS
' read analog voltage with one pin gnd, all floating then one pin at 3.3V
' header wrong way around will give a narrow range of voltages ~1.16V
PRINT
PRINT "Testing for correct orientation"
SETPIN 13, AIN
SETPIN 3, DOUT
PIN(3) = 0
PRINT "Analog range from ";STR$(PIN(13),2,2);" > ";
SETPIN 3, OFF
PRINT STR$(PIN(13),2,2);" > ";
SETPIN 3, DOUT
PIN(3) = 1
v = PIN(13)
PRINT STR$(v,2,2)
PRINT "A range from 0.2 to 2.9 is good."
PRINT
SETPIN 3, OFF
SETPIN 13, OFF

IF v < 2 THEN
  PRINT "It doesn't look right!!"
  PRINT "Giving up on the tests."
ELSE
  PRINT "Testing Digital IN"
  ' toggle one pin high/low and check that each pin follows.
  SETPIN 40, DOUT
  FOR k = 0 TO 26
    testpin = pintest(k)
    SETPIN testpin , DIN
    PIN(40) = 1
    IF PIN(testpin ) <> 1 THEN PRINT "Pin ";testpin ;" failed DIN high" : bug = bug+1
    PIN(40) = 0
    IF PIN(testpin ) <> 0 THEN PRINT "Pin ";testpin ;" failed DIN low" : bug = bug+1
    SETPIN testpin , OFF
  NEXT k
 
  SETPIN 38, DOUT
  testpin = 40
  SETPIN testpin , DIN
  PIN(38) = 1
  IF PIN(testpin ) <> 1 THEN PRINT "Pin ";testpin ;" failed DIN high" : bug = bug+1
  PIN(38) = 0
  IF PIN(testpin ) <> 0 THEN PRINT "Pin ";testpin ;" failed DIN low" : bug = bug+1
  SETPIN testpin , OFF
  SETPIN 38, OFF
 
  PRINT
  PRINT "Testing Digital OUT"
  ' toggle each pin in turn and check that output follows.
  SETPIN 40, DIN
  FOR k = 0 TO 26
    testpin = pintest(k)
    SETPIN testpin , DOUT
    PIN(testpin) = 1
    IF PIN(40 ) <> 1 THEN PRINT "Pin ";testpin ;" failed DOUT high" : bug = bug+1
    PIN(testpin) = 0
    IF PIN(40 ) <> 0 THEN PRINT "Pin ";testpin ;" failed DOUT low" : bug = bug+1
    SETPIN testpin , OFF
  NEXT k
 
  SETPIN 38, DIN
  testpin = 40
  SETPIN testpin , DOUT
  PIN(testpin) = 1
  IF PIN(38 ) <> 1 THEN PRINT "Pin ";testpin ;" failed DOUT high" : bug = bug+1
  PIN(testpin) = 0
  IF PIN(38 ) <> 0 THEN PRINT "Pin ";testpin ;" failed DOUT low" : bug = bug+1
  SETPIN testpin , OFF
  SETPIN 38, OFF
 
  PRINT
  PRINT "Testing Analog IN"

'  for k = 0 to 26
'testpin = pintest(k)
'  setpin testpin,din

'next k

  ' testing analog in.
  ' set one pin high and one pin low to give VCC/2 at the common point.
  SETPIN 3, DOUT
  SETPIN 5, DOUT
 
 
  PIN(3) = 1
  PIN(5) = 0



  FOR n = 0 TO 11
    testpin = apins(n)
    SETPIN testpin, AIN
    v = PIN(testpin)
    IF V < 1.55 OR V > 1.75 THEN PRINT "Pin ";testpin ;" failed AIN - ";v : bug = bug+1
    SETPIN testpin, OFF
  NEXT n
  SETPIN 3, OFF
  SETPIN 5, OFF
 
  PRINT
  IF bug = 0 THEN
    PRINT "All tests completed with no errors"
  ELSE
    PRINT "A total of ";bug; " errors detected over all tests!!!"
  ENDIF
ENDIF
PRINT




Try deleting the comments
Edited 2020-08-12 11:49 by bigmik
Mick's uMite Stuff can be found >>> HERE (Kindly hosted by Dontronics) <<<
 
Womble

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Joined: 09/07/2020
Location: United Kingdom
Posts: 267
Posted: 02:43am 12 Aug 2020
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Thanks for your comments Mick, I will give that code a try.
  bigmik said  I used 220R for mine..

That was my original thought.  However I didn't have enough of them, and there was this big bag of resistors which I had wombled away.  So I went for 1.2K
 
TassyJim

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Joined: 07/08/2011
Location: Australia
Posts: 6283
Posted: 02:50am 12 Aug 2020
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I was too tight with my test for analogue.

change
IF V < 1.58 OR V > 1.7 THEN PRINT "Pin ";testpin ;" failed AIN - ";v : bug = bug+1

to
IF V < 1.25 OR V > 1.9 THEN PRINT "Pin ";testpin ;" failed AIN - ";v : bug = bug+1


The lower the resistance value chosen, the closer the reading will be to Vcc/2

All your pins gave the same result so it is save to say they are working as expected.

Jim
VK7JH
MMedit
 
Womble

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Joined: 09/07/2020
Location: United Kingdom
Posts: 267
Posted: 03:13am 12 Aug 2020
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  TassyJim said  The lower the resistance value chosen, the closer the reading will be to Vcc/2

All your pins gave the same result so it is save to say they are working as expected.

Excellent Jim, thanks for clarifying that.

My gut feeling was that they were working OK   and that the discrepancy was the resistor value I chose.

Regards

An Even Happier Womble
 
bigmik

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Joined: 20/06/2011
Location: Australia
Posts: 2950
Posted: 06:58am 12 Aug 2020
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Hi Womble, All,

I would be curious as to your result by removing the REMs that I marked in RED on the above listing.

Kind Regards

Mick
Mick's uMite Stuff can be found >>> HERE (Kindly hosted by Dontronics) <<<
 
Womble

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Joined: 09/07/2020
Location: United Kingdom
Posts: 267
Posted: 08:17pm 12 Aug 2020
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  bigmik said  I would be curious as to your result by removing the REMs that I marked in RED on the above listing.

No problem.  Here is the amended program I used, and the test results:

CMM2_40way_Test.zip
adjust the commented out code to suit.

BigMik's amendment, setting pins to DIN (as shown in red in previous post)


TassyJim's amendment, adjusting the voltage range deemed acceptable (1.25v - 1.9v)


Both the amendments:


Many thanks for your help guys  
 
bigmik

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Location: Australia
Posts: 2950
Posted: 04:53am 13 Aug 2020
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Hi Womble,

That is interesting..

Changing the SetPin to Din instead of OFF changes the reading (in your case) from 1.34v to 1.72 ish results.

But as Jim says it is a rough test for analog reads.. Different resistors would read different values..


Kind Regards

Mick
Mick's uMite Stuff can be found >>> HERE (Kindly hosted by Dontronics) <<<
 
TassyJim

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Location: Australia
Posts: 6283
Posted: 08:01am 13 Aug 2020
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Hi Mick,
There are 4 10k resistors on the I2C lines pulling the voltage high.
With low value resistors in the test setup, it is not very evident but with Wombles higher values, we get a significant change.
Its still enough to show which pins are working.

Jim
VK7JH
MMedit
 
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