Rotary H1 Module gives strange values

NETMF & Gadgeteer
1

On some random occasions this module gives me incorrect values. I am using the following code:

Dim prevCount, counts As Integer

Do
	counts = rotaryH1.GetCount()
	If prevCount <> counts Then
		Debug.Print("Prev: " & prevCount & " current: " & counts & " result: " & (prevCount - counts))
		prevCount = counts
	End If
Loop

Here are two captures:

[quote]Prev: 49 current: 57 result: -8
Prev: 57 current: 59 result: -2
Prev: 59 current: 62 result: -3
Prev: 62 current: 63 result: -1
Prev: 63 current: 61 result: 2
Prev: 61 current: 43 result: 18
Prev: 43 current: 30 result: 13
Prev: 30 current: 22 result: 8
Prev: 22 current: 11 result: 11
Prev: 11 current: -32764 result: 32775
Prev: -32764 current: -4 result: -32760
Prev: -4 current: 0 result: -4
Prev: 0 current: 12 result: -12
Prev: 12 current: 21 result: -9
Prev: 21 current: 23 result: -2
Prev: 23 current: 30 result: -7

Prev: 36 current: 33 result: 3
Prev: 33 current: 34 result: -1
Prev: 34 current: 38 result: -4
Prev: 38 current: 41 result: -3
Prev: 41 current: 39 result: 2
Prev: 39 current: 33 result: 6
Prev: 33 current: 32 result: 1
Prev: 32 current: 22 result: 10
Prev: 22 current: 19 result: 3
Prev: 19 current: 16 result: 3
Prev: 16 current: 6 result: 10
Prev: 6 current: 2 result: 4
Prev: 2 current: -32765 result: 32767
Prev: -32765 current: -9 result: -32756
Prev: -9 current: -14 result: 5
Prev: -14 current: -13 result: -1
Prev: -13 current: -10 result: -3[/quote]

Value of 32767 does look suspicious. Can anyone provide any explanation why I am getting this?

Btw, same happens without using Debug.Print.

2

The module is running in 16bit mode so once it gets to 32768 it goes to 0

1 Like
3

Looks like an overflow issue. I would get the driver source code and check there.

4

Yes, it only happens when .GetCount is around 0. It does not happen if .GetCount is, for example, at 1000.

5

You need to handle when the count gets to max and min

6

@ Bill Gates - But that is not max or min, that is in the middle. I think Gadgeteer driver should not give this type of result.
I have looked at its driver and I am pretty sure that if statement is the cause of this issue.

public int GetCount()
{
	int count = this.Read2(Commands.LS7366_READ | Commands.LS7366_CNTR);

	if ((this.GetStatus() & 0x01) > 0)
	{
		count = ~count;
		count &= 0x7FFF;
		count *= -1;
	}

	return count;
}
7

I must be blind - well it is monday ::slight_smile:

Where is the issue?

Get count returns the current count from the LSI chip which is a INT16

8

So turning it anti clockwise once you get to zero it will be -32768

9

No.

[quote]
Prev: 0 current: 1 result: -1
Prev: 1 current: 2 result: -1
Prev: 2 current: 3 result: -1
Prev: 3 current: 4 result: -1
Prev: 4 current: 3 result: 1
Prev: 3 current: 2 result: 1
Prev: 2 current: 1 result: 1
Prev: 1 current: 0 result: 1
Prev: 0 current: -1 result: 1
Prev: -3 current: -4 result: 1
Prev: -4 current: -5 result: 1
Prev: -5 current: -4 result: -1
Prev: -4 current: -3 result: -1
Prev: -3 current: -2 result: -1
Prev: -2 current: -1 result: -1
Prev: -1 current: 0 result: -1
Prev: 0 current: -1 result: 1
Prev: -1 current: 0 result: -1
Prev: 0 current: 1 result: -1
Prev: 1 current: 2 result: -1
Prev: 2 current: 3 result: -1[/quote]

It only happens if I turn more than once in one go. If I turn it one-by-one it works fine.

10

Dunno then - call the experts :smiley:

11

@ John, ring ring… :whistle:

12

@ iamin - If you change the function to the one below, does it work as expected for you?


public int GetCount()
{
	return this.Read2(Commands.LS7366_READ | Commands.LS7366_CNTR);
}
13

@ John - Yes, it does the trick.
While you at, maybe you could add ResetCount method that is already included in the Pulse Count module?

14

@ iamin - It’s been added.

1 Like