im thinking about an interesting project of getting one of my favorite guitar pedals under control, im wondering about the feasibility of connecting the 7-segment display on my guitar pedal as input into my arduino.
I have two possible thoughts on this module.
first i was thinking i could individually read analog values of each of the wires that leave the main board that go to the individual pins 7-segment led displayand decrypt the value ( probably with mux shield to add more inputs from sparkfun, and then i had another thought a few months later of using the same trick as a cheap keypad and use relays connected instead of the 7-segment display to trick the guitar pedal to drive a logic system.
i have read about using multiple buttons on the same analog pin by using different resistor values attached to switches in a ladder where combinations of button presses can share the same pin.
the big question for me is what method is going to be getting the right combination to read speed, to detect the codes "EDIT" "PLAY" "BYPASS" "A1"-"F4" fast enough to decrypt the values on the displays ( 2 characters per pedal). to enable usb editing of the network of guitar pedals (and backup of patches.)
can anyone chime into this topic with some ideas they would have,
and also i have investigated the board of the guitar pedal the ZOOM 505 and i cant find the specific chip that sends data to the driver for the display, so I will need to treat the display as the only source of feedback to the arduino.
thats why so far im thinking that ill be using one of my mega to accomplish this and still have room for the midi and possibly a display for the interpreted data.( ie needing to repeat the captured displays onto a serial display) and then to add overkill for input pins a mux shield from sparkfun would add enough for network of relays to trick the pedals into thinking the arduino is human interaction.
but right now this is still in piles of prototypes stage, where i have built the relay network and the Ucontroler for the pedal, and a mega with a midi splitter merger sketch i made.
but i am well, torn on how and how much money i need to finish this off and still have a functional rackmounted guitar pedal controller considering the cost of the end enclosure and display module
Hi, well i don't know much about guitar pedals but it sounds like your over complicating things
every problem has a simple solution.
so i think firstly what do you want to achieve?
does the pedal output midi instructions?
So, the reason for a need to read the 2character display is to add MIDI like control over an analog guitar pedal. At the moment I use a lot of MIDI gear but the zoom 505 is not MIDI in any way. I own several of these style of guitar pedals. The sum of their user interaction is 6 buttons that get used to control menus and change preset audio banks and a 2 character display, and a modulaton pedal input.
Since I already made the arduino control the pedal blindly, I'd like to have my arduino be aware of what the display reads.
Currently I have the zoom pedal under relay control and resistance control. Aka I simulate the same events as someone stepping on the buttons or using the modulation input as if someone's stepping on a volume pedal. This works great for line of sight use, but if i can't see the display I'm just hitting buttons via a fancy remote and each button does different things per mode. What i want is to eventually rackmout a heavily modified guitar pedal to get its editing mode under pc control. So if its batteries die.. loss theft... Etc ill still have my preset banks. And on a pc ill be able to share my prearranged without expecting a guitarist a day overwritng their prearranged to try mine.
So the arduino must know what mode the pedal is in. By the graphical display. In play modes the relays change the presets. And there are multiple sub modes. Ie sequence switch where you can go up and down all presets or performance where you select preset then numbers flash so you can go from preset 1 to 9 without hearing prearranged 2-8. And edit mode uses same buttons in different patterns to navigate a menu with a 2char display. If the arduino knew it was edit mode I could simply do away with the display on the pedal and use an interface on arduino or on a laptop so there's no need to keep pedals on floor.
Yes zoom makes MIDI gear. And its not a comparison. The real pedals are more robust sounding than rackmount.
OK, I'll give a few "thoughts". Partly because I was pondering a similar problem in "reading" a bathroom digital scales.
Two digits... if it is real 7seg LEDs we have 14 wires we simply couple to 14 Arduino pins. The high impedance of the input should make it safe enough. But the voltage drop across the LED is only a volt or so, so you need some level shift circuit (single transistor amplifying circuit). Not my area of expertise.
If the LEDs are driven by some simple steady state signal, then it is real easy with the program. Just make a lookup table of the 10 different combinations that are valid digits, scan for a match, the offset in the table is the digit value.
No, I suspect the real problem is that the segments are probably driven by some multiplexing circuit, so that the program and electronics need to monitor the state of the common line (whether Common Anode or Cathode) and when it is "on" for that digit, then sample the other lines. There may be challenges with the timing. Could be solved with an ISR.
But definitely doable, I think. Worth the trouble? Maybe, because it will take a few days.