Understanding the Hydra Switches - Schematic Analysis

[airbud]

Found this schematic of the Hydra circuit in the forum, and I'm trying to understand how the switches work in tandem with the FV1. Pins 16, 17 and 18 (S0, S1 and S2 respectively) are connected to three of the switches, one each. The pinouts refer to these as related to program selection, so I'm imagining that when the heads are turned on or off it's actually a different program on the EEPROM. I've been wondering how 1P8T switches work for these FV1 circuits as well, but admittedly haven't checked out a schematic of one yet (guess I'll go check this out later on today).

More of a discussion question than a specific one, but as I finish the dev board I'm working to gain a better understanding of designing around the FV1. Maybe "how does one integrate switches and other non-pot controls into an FV1 design?"

Thanks in advance for any thoughts!

Unconfirmed Hydra Schematic


FV1 Pinout

 

[Robert]

S0, S1, and S2 set a binary value to select one of the eight FV-1 programs.

0, 0, 0 = Program 0
0, 0, 1 = Program 1
0, 1, 0 = Program 2
0, 1, 1 = Program 3
1, 0, 0 = Program 4
1, 0, 1 = Program 5
1, 1, 0 = Program 6
1, 1, 1 = Program 7

0 meaning LOW, or 0V / GND
1 meaning HIGH, or 3.3V


In the Hydra each of the combinations of playback heads is a separate program, with one exception... the fourth head switch.

Since the FV-1 only supports eight programs (and three program select switches) there had to be a workaround to get that fourth head switch functional. Each of the eight programs / combinations also includes the fourth head as part of their algorithm. The fourth toggle switch is connected to one of the potentiometer inputs and behaves as an "all or nothing" volume control for the fourth head. It's always active in every combination, but when the switch is off the volume for that tap is at minimum.

The FV-1 projects here that utilize the 1P8T rotary switch use a matrix of diodes so that the proper combination of S0, S1, S2 is pulled high or low to correspond to the position of the rotary switch. There are cleaner ways of doing it using a microcontroller or BCD counter IC, but I felt like using common every day diodes would make parts sourcing easier.

 

[airbud]

S0, S1, and S2 set a binary value to select one of the eight FV-1 programs.

0, 0, 0 = Program 0
0, 0, 1 = Program 1
0, 1, 0 = Program 2
0, 1, 1 = Program 3
1, 0, 0 = Program 4
1, 0, 1 = Program 5
1, 1, 0 = Program 6
1, 1, 1 = Program 7

0 meaning LOW, or 0V / GND
1 meaning HIGH, or 3.3V


In the Hydra each of the combinations of playback heads is a separate program, with one exception... the fourth head switch.

Since the FV-1 only supports eight programs (and three program select switches) there had to be a workaround to get that fourth head switch functional. Each of the eight programs / combinations also includes the fourth head as part of their algorithm. The fourth toggle switch is connected to one of the potentiometer inputs and behaves as an "all or nothing" volume control for the fourth head. It's always active in every combination, but when the switch is off the volume for that tap is at minimum.

The FV-1 projects here that utilize the 1P8T rotary switch use a matrix of diodes so that the proper combination of S0, S1, S2 is pulled high or low to correspond to the position of the rotary switch. There are cleaner ways of doing it using a microcontroller or BCD counter IC, but I felt like using common every day diodes would make parts sourcing easier.

thanks Robert!!! this is exactly the answer i needed. i saw that one switch was set up differently and was wondering how that was working, nice workaround!

i remember seeing that diode setup, this makes so much more sense now! excited to mess around with programming my own algorithms.