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Microcontroller and FV1 in parallel
Posted: Mon Sep 04, 2023 10:21 pm
by smear
I'd like to use a microcontroller and an FV1 together. I know that normally, you should just connect all the controls to the microcontroller, and then output those values from the microcontroller to the FV1.
But some microcontrollers have a small number of pins. Sometimes, it'd be easier to connect a pot or a mode switch to both the microcontroller and the FV1. That way, both chips can read the same value.
Are there any risks if I connect a microcontroller input pin and an FV1 input pin together? I'd probably want to disable any pullup resistors on the microcontroller. But other than that?
In an idea world, I'd use some buffers to isolate them, but at that point a bigger microcontroller might make more sense...
Re: Microcontroller and FV1 in parallel
Posted: Wed Sep 06, 2023 3:31 am
by ice-nine
You will first need to make sure your microcontroller is a 3.3v device, if you use a 5v device like an Arduino Nano it is a 5v micro and will need to have 5v-3.3v level shifters. Easier to use a 3.3v Micro so no need for level shifters.
Re: Microcontroller and FV1 in parallel
Posted: Wed Sep 06, 2023 11:08 pm
by smear
ice-nine wrote: ↑Wed Sep 06, 2023 3:31 am
You will first need to make sure your microcontroller is a 3.3v device, if you use a 5v device like an Arduino Nano it is a 5v micro and will need to have 5v-3.3v level shifters. Easier to use a 3.3v Micro so no need for level shifters.
Thanks for the reply! I'll use a microcontroller chip directly, not an Arduino or similar board. The Atmega328p runs fine on 3.3V so should be good.
I'm specifically curious if i connect the wiper of a voltage divider to
both an FV1 pot pin
and an Atmega328p input pin. Could the analog read of the microcontroller interact with the fv1's own reading in any way?
Looking at the
Atmega328p datasheet, I notice the input circuit for the analog input is listed in section 23.6.1. That section also states "An analog source applied to ADCn is subjected to the pin capacitance and input leakage of that pin... The ADC is optimized for analog signals with an output impedance of approximately 10kΩ or less."
I notice FV1's pot inputs have an impedance of ~15MΩ. so they seem pretty robust. But I still worry there might be some source of issue i'm not considering?
Re: Microcontroller and FV1 in parallel
Posted: Thu Sep 07, 2023 8:02 am
by frank
Use a lower POT value like 5K and it should be fine. The only real issue I can think of is using a POT value at the top of the range like 10K as that may supply enough current for one of the converters but not both so they would current starve.
Re: Microcontroller and FV1 in parallel
Posted: Fri Sep 08, 2023 9:23 am
by smear
frank wrote: ↑Thu Sep 07, 2023 8:02 am
Use a lower POT value like 5K and it should be fine. The only real issue I can think of is using a POT value at the top of the range like 10K as that may supply enough current for one of the converters but not both so they would current starve.
Oh good point, didn't think of that! Thanks very much for the insight
Re: Microcontroller and FV1 in parallel
Posted: Fri Sep 08, 2023 9:52 am
by ice-nine
smear wrote: ↑Wed Sep 06, 2023 11:08 pm
ice-nine wrote: ↑Wed Sep 06, 2023 3:31 am
You will first need to make sure your microcontroller is a 3.3v device, if you use a 5v device like an Arduino Nano it is a 5v micro and will need to have 5v-3.3v level shifters. Easier to use a 3.3v Micro so no need for level shifters.
Thanks for the reply! I'll use a microcontroller chip directly, not an Arduino or similar board. The Atmega328p runs fine on 3.3V so should be good.
I'm specifically curious if i connect the wiper of a voltage divider to
both an FV1 pot pin
and an Atmega328p input pin. Could the analog read of the microcontroller interact with the fv1's own reading in any way?
Looking at the
Atmega328p datasheet, I notice the input circuit for the analog input is listed in section 23.6.1. That section also states "An analog source applied to ADCn is subjected to the pin capacitance and input leakage of that pin... The ADC is optimized for analog signals with an output impedance of approximately 10kΩ or less."
I notice FV1's pot inputs have an impedance of ~15MΩ. so they seem pretty robust. But I still worry there might be some source of issue i'm not considering?
I have used the pot wiper pin connected directly to both the FV-1 and a micro with no problem at all when run at 3.3v.
Re: Microcontroller and FV1 in parallel
Posted: Mon Feb 19, 2024 9:57 pm
by smear
ice-nine wrote: ↑Fri Sep 08, 2023 9:52 am
smear wrote: ↑Wed Sep 06, 2023 11:08 pm
ice-nine wrote: ↑Wed Sep 06, 2023 3:31 am
You will first need to make sure your microcontroller is a 3.3v device, if you use a 5v device like an Arduino Nano it is a 5v micro and will need to have 5v-3.3v level shifters. Easier to use a 3.3v Micro so no need for level shifters.
Thanks for the reply! I'll use a microcontroller chip directly, not an Arduino or similar board. The Atmega328p runs fine on 3.3V so should be good.
I'm specifically curious if i connect the wiper of a voltage divider to
both an FV1 pot pin
and an Atmega328p input pin. Could the analog read of the microcontroller interact with the fv1's own reading in any way?
Looking at the
Atmega328p datasheet, I notice the input circuit for the analog input is listed in section 23.6.1. That section also states "An analog source applied to ADCn is subjected to the pin capacitance and input leakage of that pin... The ADC is optimized for analog signals with an output impedance of approximately 10kΩ or less."
I notice FV1's pot inputs have an impedance of ~15MΩ. so they seem pretty robust. But I still worry there might be some source of issue i'm not considering?
I have used the pot wiper pin connected directly to both the FV-1 and a micro with no problem at all when run at 3.3v.
Awesome, thanks!
All seems to be working for me