Micro controlled program select - odd behavior

Hardware questions and issues with the FV-1

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amongstmyselves
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Micro controlled program select - odd behavior

Post by amongstmyselves » Mon Dec 14, 2015 8:23 pm

Hi,

I've made a nice effects unit which contains a SKRM-ETAP2 module.

I am using an Arduino Nano micro to control the program select. The problem is that the program on the SKRM module doesn't change every time I change the program on the Arduino. It changes some times but not others.

I have 3 digital outputs of the Nano attached to S0, S1 and S2 via a resistor divider to give me 3.3v. These outputs are set by an up and down push button. Additional to this are eight leds which indicate the selected program.

I've checked the output logic going to the SKRM module with leds and it all appears to change here.

I did think that maybe the Nano wasn't changing each of the outputs fast enough for the SKRM so I made the output changes as fast as I can using direct port addressing to no avail.

Any suggestions would be appreciated.

Steve.

frank
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Post by frank » Mon Dec 14, 2015 11:13 pm

What are the voltages at the S0, S1 and S2 pins of the SKRM module? You said you are using a voltage divider so you may need to adjust the values to make sure you are at gnd and 3.3V
Frank Thomson
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amongstmyselves
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Post by amongstmyselves » Tue Dec 15, 2015 6:52 pm

Yep. There's the problem. Only measuring 1.98V at the S0, S1 and S2 pins on the SKRM module.

Is this due to the 10k pulldown resistor on the SKRM ?

I know this is outside of the forums purpose but what would be the solution to this ?

Thanks,

Steve

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Post by frank » Tue Dec 15, 2015 8:18 pm

Well, you said you are using a voltage divider for the signals so adjust it to give you 3.3V at the pins when they are high. Without a lot more info like a schematic, the voltage you are dividing down from, etc. not much else to suggest.
Frank Thomson
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amongstmyselves
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Post by amongstmyselves » Tue Dec 15, 2015 8:47 pm

Seems to be something else causing this problem. With the resistor divider not connected to the SKRM I get 3.3v but when connected I get 1.99V ?

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Post by frank » Wed Dec 16, 2015 8:15 am

As I said we need to see schematic, etc. to be of any more help.
Frank Thomson
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amongstmyselves
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Post by amongstmyselves » Wed Dec 16, 2015 1:07 pm

Sorry Frank, I meant to add "I presumed my pcb was fine but I'll have to check it for any shorts first." at the end of my last message.

amongstmyselves
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Post by amongstmyselves » Thu Dec 17, 2015 8:21 pm

Had another chance to attempt a fix on this issue. I've attached my schematic for the Arduino controller side of things. I simply attach the shown schematic directly to S0, S1 and S2.

While I was at it I breadboarded the schematic that the guy who created the eTap2 universal hardware controller used. I've attached the basic schematic of this showing a 1N4148 coming from the arduino digital output. Difference here is that the 3.3v is referenced from the SKRM. Sorry the ground is connected from J1 to the Arduino.

The etap2 has the correct voltage at S0 whereas mine has only 1.99V.

My hunch is that the reference to 0v is different on both units ? Beyond my simple understanding of electronics.

Here's my schematic:-

Image

Here's the etap2 controller - simplified - note 1k5 resistor:-
Image

frank
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Post by frank » Thu Dec 17, 2015 11:00 pm

Since the SKRM has the 10K to ground on the select pins you will need to adjust the values you are using for the voltage divider. The 20K from the divider is basically in parallel with the 10K on the board which will result in an effective resistance of less than 10K. So you need to calculate the proper values for the voltage dividers keeping in mind the 10Ks on the SKRM board.
Frank Thomson
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micahvdm
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Post by micahvdm » Thu Dec 17, 2015 11:28 pm

Have a look at this:
http://www.echotapper.nl/wp/wp-content/ ... G_0515.png
I would suggest using the logic port setup in this image.
You can use the 3.3v tap on the skrm pins(pin 6)
So that would be:

adruino digital pin -> diode -> FV-1 S0
|
->1.5k resistor -> 3.3v tap

Rinse and repeat this for S0-S2.
scrap the 10k and 20k resistors and just use the 3.3v from the skrm module!!

amongstmyselves
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Post by amongstmyselves » Sun Dec 20, 2015 2:30 pm

Thanks Frank. I did suspect the pull down might be the issue.

Thanks micahvdm. That is the other schematic I have shown which as you point out comes from the etap2.

Problem solved I'd say !

Cheers,

Steve

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