wickedblade
Differences
This shows you the differences between two versions of the page.
| Both sides previous revisionPrevious revisionNext revision | Previous revision | ||
| wickedblade [2009/09/20 21:25] – WickedBlade | wickedblade [2011/11/29 14:40] (current) – old revision restored (spam kill) smashtv | ||
|---|---|---|---|
| Line 38: | Line 38: | ||
| * [[http:// | * [[http:// | ||
| * [[http:// | * [[http:// | ||
| + | |||
| + | Pedalboards that resemble what I'm doing here: | ||
| + | * Fractal Audio Systems MFC101 | ||
| + | * [[http:// | ||
| ===== Major design changes ===== | ===== Major design changes ===== | ||
| Line 45: | Line 49: | ||
| * channel switching, originally CMOS based (not working!) now uses relays | * channel switching, originally CMOS based (not working!) now uses relays | ||
| * went from 8 to 10 effect loops, it will be stuffy but I think I can get it all to fit and still be particable(and be able to physically separate the signal out from the digital circuits) | * went from 8 to 10 effect loops, it will be stuffy but I think I can get it all to fit and still be particable(and be able to physically separate the signal out from the digital circuits) | ||
| + | * went from 2 to 4 custom control footswitches | ||
| ===== User needs ===== | ===== User needs ===== | ||
| - | What I want is a pedalboard that handles banks of 5 patches, plus an additionnal tap tempo footswitch, and 2 additional custom control footswitches (more on that later). | + | What I want is a pedalboard that handles banks of 5 patches, plus an additionnal tap tempo footswitch, and 4 additional custom control footswitches (more on that later). |
| So I need a total of 12 footswitches: | So I need a total of 12 footswitches: | ||
| Line 64: | Line 69: | ||
| - | === Custom controls === | + | === Custom controls |
| - | So how do the custom controls footswitches work? Basically, for any patch, you can specify that the custom controls will toggle the state of any of the loops, and you can specify | + | So how do the custom controls footswitches work? Basically, for any patch, you can specify that the custom controls will toggle the state of any of the loops, and you can specify |
| - | I like this idea, because it offers the same kind of flexibility as having a switch for each and every loop, but in a smaller package. I doubt that I would need more than 2 custom controls. I could probably go up to 4 custom controls, since I have some room left on the chassis for 2 more footswitches, | + | I like this idea, because it offers the same kind of flexibility as having a switch for each and every loop, but in a smaller package. I doubt that I would need more than 2 custom controls. I will probably go up to 4 custom controls, since I have some room left on the chassis for 2 more footswitches, |
| Line 118: | Line 123: | ||
| * 1 DINx4 module, to handle the footswitches and the edition buttons/ | * 1 DINx4 module, to handle the footswitches and the edition buttons/ | ||
| * 2 DOUTx4 modules to handle the relays, the status LEDs and the 7-segment digits LEDs. 1 module is not enough, but I probably won't need to fully populate the 2nd DOUTx4, but it's nice to have the option of more DOUTs | * 2 DOUTx4 modules to handle the relays, the status LEDs and the 7-segment digits LEDs. 1 module is not enough, but I probably won't need to fully populate the 2nd DOUTx4, but it's nice to have the option of more DOUTs | ||
| - | * 1 bankstick, of which I will probably need only one EPROM (see next section)... | + | * 1 bankstick, of which I will probably need only 2 EPROM chips (see next section)... |
| Here is the detail of what is going to be connected to the DIN/DOUT. | Here is the detail of what is going to be connected to the DIN/DOUT. | ||
| Digital inputs: | Digital inputs: | ||
| - | * 12 footswitches (bank up/down, patches A..D, tap tempo, custom controls | + | * 12 footswitches (bank up/down, patches A..D, tap tempo, custom controls |
| - | * 2 rotary encoders for edition (parameter select, parameter value change), that means 2x4 inputs | + | * 2 rotary encoders for edition (parameter select, parameter value change), that means 2x2 inputs |
| * 2 buttons (edit/ | * 2 buttons (edit/ | ||
| * possibly 2 inputs to know if expression pedals are plugged | * possibly 2 inputs to know if expression pedals are plugged | ||
| - | This amounts to a maximum total of 24 digital inputs. | + | This amounts to a maximum total of 20 digital inputs |
| Digital outputs: | Digital outputs: | ||
| Line 141: | Line 146: | ||
| * 12 relays for loops and buffers activation, on 2 separate shift registers, so that's actually consuming 16 outputs | * 12 relays for loops and buffers activation, on 2 separate shift registers, so that's actually consuming 16 outputs | ||
| * 12 status LEDs for the loops/ | * 12 status LEDs for the loops/ | ||
| - | * 2 relays for channel switching operation | + | * 2 relays for channel switching operation |
| * 2 7-segments LED digits, 8 inputs per digit, so that's 2x8 outputs | * 2 7-segments LED digits, 8 inputs per digit, so that's 2x8 outputs | ||
| * 5 status LEDs showing which patch is activated | * 5 status LEDs showing which patch is activated | ||
| Line 165: | Line 170: | ||
| But this is the maximum continuous current draw, we have to take the pikes into account too. I've been told that aiming at 2A is a good choice, so I'll try to do that. | But this is the maximum continuous current draw, we have to take the pikes into account too. I've been told that aiming at 2A is a good choice, so I'll try to do that. | ||
| - | I originally | + | As far as voltage is concerned, the PIC and associated ICs need 5V, the relays need 5V too, but for the input/ |
| - | Since then, I found a 5V 2A power supply (PETERSON POWER SUPPLY 5V 2A at Thomann), which is significantly more expensive, but ensures that I won't have power supply problems. Also, the 5V input voltage means that the 7805 won't heat much, I think. | + | |
| - | + | ||
| - | I also found a 9V 2A unit: THOMANN NT 092A, similarly priced. | + | |
| - | + | ||
| - | I thought for a time that I could forget about these power supply units: the Sony PSP portable console uses a 5V 2A power supply, so that means that there are many that are readily available in video game stores, | + | |
| It appears to me that I need to manage 2 separate grounds for analog signal and digital signal. I don't quite know how to do that. I've been told I could put some kind of low pass filter somewhere, but I don't quite know how and where. I believe this should go between the digital and analog grounds, so that the analog ground gets a filtered version of the digital ground, but how should I go about it? | It appears to me that I need to manage 2 separate grounds for analog signal and digital signal. I don't quite know how to do that. I've been told I could put some kind of low pass filter somewhere, but I don't quite know how and where. I believe this should go between the digital and analog grounds, so that the analog ground gets a filtered version of the digital ground, but how should I go about it? | ||
| Line 222: | Line 222: | ||
| * a linear regulator (LM7805 or L78S05) | * a linear regulator (LM7805 or L78S05) | ||
| - | For the input and output buffers, I chose the OPA134PA | + | For the input and output buffers, I chose the OPA2134 |
| Here's the partlist for one buffer: | Here's the partlist for one buffer: | ||
| - | * 1x OPA134PA or 1xOPA2134PA | + | * 1x OPA2134PA (half of it actually) |
| * 1x DIP8 socket | * 1x DIP8 socket | ||
| * 3x 100k metal film resistors | * 3x 100k metal film resistors | ||
| Line 232: | Line 232: | ||
| * 2x 10µF electrolytic capacitors | * 2x 10µF electrolytic capacitors | ||
| - | Note that I have to double the quantities because I want 2 buffers. Again, more information can be found on [[http:// | + | Note that I have to double the quantities because I want 2 buffers |
| - | For channel switching I originally thought about using a CD4053 like geofex does, but it needs a -5V input besides the +5V and ground. And I don't have that. It doesn' | + | For channel switching I have considered |
| - | Here's a topic I opened on the forum on this matter: [[http:// | + | Another option is the "solid state relays", |
| - | + | ||
| - | I'm now turning my hopes to the "solid state relays", | + | |
| From the Fender Hot Rod Deluxe schematics, I gather that to drive the " | From the Fender Hot Rod Deluxe schematics, I gather that to drive the " | ||
| Line 243: | Line 241: | ||
| * 2 47ohms 1/4W 5% resistors | * 2 47ohms 1/4W 5% resistors | ||
| * 2 22uF/25V electrolytic caps | * 2 22uF/25V electrolytic caps | ||
| - | The schematics can be found easily on the net. Amps differ widely as far as channel switching is concerned, so better check the schematics to match your amp! | + | The schematics can be found easily on the net. Amps differ widely as far as channel switching is concerned, so you' |
| ==== Loops wiring ==== | ==== Loops wiring ==== | ||
| Line 261: | Line 259: | ||
| * The SDCC compiler doesn' | * The SDCC compiler doesn' | ||
| * PIC limitations mean that you can't declare variables that use more than 256 bytes in RAM. This is the cause of the unintelligible linker error message "no target memory available for < | * PIC limitations mean that you can't declare variables that use more than 256 bytes in RAM. This is the cause of the unintelligible linker error message "no target memory available for < | ||
| - | * Compiling for the 18f4620 makes the linker output warnings about unrecognized PIC and using the generic PIC18cxx type. The warnings are apparently considered ok to ignore. I personally don't think warnings are ok in any from, but hey, I'm not coding the gputils or SDCC... | + | * Compiling for the 18f4620 makes the linker output warnings about unrecognized PIC and using the generic PIC18cxx type. The warnings are apparently considered ok to ignore. I personally don't think warnings are ok in any from (and I fixed them, search the forum), but hey, I'm not coding the gputils or SDCC... |
| * Code:: | * Code:: | ||
| + | * It's often better to use a lot of //if// statements than //switch// statements, because the latter have a non-negligible overhead. Also, it is often much more efficient (memory-wise as well as performance wise) to use arrays where applicable. | ||
| + | * Because of the banked structure of memory in the PIC, you should take special care where you put your data to avoid unnecessary BANKSEL instructions (these are the one that select a particular bank in assembly language). Similarly, I found that it's often better to work on a local copy (into a local variable) of a volatile global variable, than using it repeatedly: the compiler has no way of knowing if an interrupt routine has modified it and will read it back too often, including using BANKSEL instructions. Remember that declaring a local variable doesn' | ||
| + | * The optocoupler in the CORE module (a 6N138) is a fragile thing, so buy a few spares, just in case | ||
| + | * For use as a computer MIDI interface, you really need either a gameport MIDI cable (if you motherboard has a gameport) or a USB MIDI cable. I now know for a fact that my Line6 PODxt and my Boss DR-880 can't be trusted, even though they sport USB and MIDI outputs. The PODxt filters out SysEx messages and I couldn' | ||
| + | * Noise! It turns out that having the DOUT modules chained is a recipe for noise. Specifically 1kHz noise (if that's the frequency to which you set the shift registers refresh). After a hard time investigating, | ||
| + | * The documentation about MIOS_BANKSTICK functions is unclear about that, but it seems that if you want to use the page reading/ | ||
| + | * I would have dearly loved to know about the watchdog timer (WDT) before, that would have helped me understand why my app kept rebooting while it was trying to initialize the banksticks! Days on debugging have been wasted on this :( | ||
| + | |||
| + | |||
| + | |||
wickedblade.1253481946.txt.gz · Last modified: 2009/09/20 21:25 by WickedBlade