Joined: Jun 28, 2006
Location: Tasmania, Australia
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|Posted: Wed Aug 02, 2006 10:51 pm Post subject:
Successful 2x Memory Expansion for Casio SK5 and SK8!!
|Well, it's been a very successful and productive afternoon! I've now got a fully working, SK8 with DOUBLE the sampling capacity of the original!
Here's my step by step How-To for the SK5 and SK8.
2x Memory Expansion for Casio SK5 and SK8 -- by Graham Meredith
This was an attempt for me to understand memory chip control, and how to access them. Plutoniq9's 32x memory expansion in the Yahoo Casio SK Groups is a much larger, better and more elegant way of doing memory expansions, but I wanted to have a go at this one first, and then try his one when I got mine working.
I now have 2 RAM chips installed in my Casio SK8 - the original SK8 chip (the uPD43256), and the new chip (the Dallas DS1230Y-150), stacked on top of each other, with a switch and 2 resistors to switch between the 2 chips.
This has given me 2 separate banks of 4 samples - the 4 from the original chip, and now an extra 4 from the top bank.
Soldering iron, 15W (no greater – can damage the circuit tracks by excess heat)
Antistatic wrist band and cable
Texas Instruments BQ4011Y: http://focus.ti.com/docs/prod/folders/print/bq4011y.html
Hookup wires, insulated, of different colours
DPDT toggle switch
10k ¼ watt resistors – 2 of.
Put on the antistatic wrist band and cable, connect the cable somewhere to earth, such as a water tap. This will prevent static discharge building up and damaging your chip.
1. Study the pin out diagrams for each chip below. Also, examine the actual chip when you get it. Make sure you can identify which is pin 1 on the chip (it has a little embossed circle next to it with a “1” in it on the top of the chip).
2. Unplug the Casio from the power adapter, and remove the batteries. Now, switch the Casio ON to drain any residual power left in the circuits
3. Making sure the chip is placed the correct way around, solder the new chip directly onto the top of the old one, pin for pin, except for the CE pin (or CS pin on the original chip), which I bent out horizontally away from the other pins on the new chip. Disconnect the old chip's CS pin by de-soldering its track on the circuit board and isolating its pin. Please have a look at the pin outs diagrams below, and study them.
4. Solder 10k resistors to each of these CE/CS pin legs of the 2 chips. These 2 resistors then go to the 2 centre terminals of a DPDT toggle switch via lengths of insulated wire - see the wiring diagram below.
5. Solder the CE signal track wire to the CE pin track on the track side of the board, anywhere near where you desoldered the CE pin from the original chip (make sure you don't accidentally reconnect the CE pin to the circuit track again).
6. Solder the +5V supply wire directly to the exposed pin 28 leg (the +5V Vcc pin) of the original chip, as a convenient +5V supply for the switch.
7. That's basically it!
Using the sample banks
Put some batteries in the Casio, or connect it to the power adapter. Put the toggle switch in the bank 1 position (accessing the original RAM). Record some samples on the pads - any samples, using the inbuilt mic, for example. Record 4 short samples - one on each pad. Play them to confirm the recording went OK.
Now, switch the toggle switch to the bank 2 position (accessing the NEW RAM). Record 4 samples in the same way. Play them to confirm the recording went OK. Switch back to bank 1. Your bank 1 samples should still be there, ready to play!! If you have batteries installed, you can now switch off the keyboard. Switch it back on – bank 1 samples should still be there. Switch to bank 2 – they should be there also!
Minor Issues and Limitations
Memory loss from flat batteries
There is a catch, in that once you've got it working, and you've recorded samples on both banks, if your batteries go flat, the sampler will “appear” to have lost the samples stored in the new 2nd chip. It will sound the default “empty sample” sound on each pad. It actually hasn't, they're still there. But the Casio's processor has lost its directory info about where to find the samples when the batteries went flat.
To restore them, put the toggle switch in the bank 1 position (accessing the original RAM). Record some samples on the pads - any samples, using the inbuilt mic, for example, but in the same layout that you recorded the samples on the new bank chip - ie. samples 1 and 2, long or short, samples 3 and 4, long or short. Play them to confirm the recording went ok.
Now change the bank switch. Your 2nd bank samples should now be there, just as you left them, before your batteries went flat. So, you only have to do this if the battery power fails, or if you use an AC adapter without batteries in the keyboard. Normally, both banks samples will be there as soon as you switch it on, with good batteries installed. The new chip remembers the samples EVEN when there is no power or flat batteries.
Remember, though, that the OLD chip won't - it will remember them when switched off only while you still have good batteries in it, just like it always did.
I have installed rechargeable nicad batteries in my SK8, and soldered in an extra charging socket, so I can recharge without having to disconnect the batteries and remove them, when I hear them start to go flat.
Different length samples in different banks
If you recorded 4 short samples in bank 2 first, and then 2 long samples in bank 1, you will find the sample playback a bit strange when you shift back to bank 2. Try it – it makes for some interesting sample playback. Sample 1 pad will play back both sample 1 and then sample 2, straight after it! That’s because the sample length playback settings are NOT stored in the RAM, but in the processor itself – the same reason for the “memory loss from flat batteries” issue above. The processor remembers the LAST layout recorded.
How to fix it:
You have to re-sample on an unwanted bank, the same pad length duration and pad layout as in the bank you want to keep. For example, if you want to keep the samples in bank 2, and restore them to proper playback, switch to bank 1, and record any sample, but in the same pad and length layout that you KNOW bank 2 has. It means you lose your samples on bank 1, though.
There is actually a way to preserve ALL the banks layouts, even if they’re different. You can connect a Memory Protect Switch on the chips. Plutoniq9 has created this setup for his memory expansion, which has these same issues. It involves isolating the WE (write enable) pins on each chip, and putting a toggle switch in, and toggle between the 2, with 2x 10k resistors, set up similarly in the way the CE toggle switch is set up. You can then DISABLE a chip from being overwritten. I’ve tried this, it works, but I haven’t documented it yet.
You select the bank you want to restore the sample pad layout to, switch the memory protect switch ON, and then do a false recording onto the sample pads, with the same sample length and layout for each pad, that you remember the pads really have. You press the “sample/sample long” button, you will hear the keyboard go “ding” as if it has accepted your sample, but when you play back the pad, it will have your original sample there instead, laid out correctly. Remember to switch memory protect to OFF, though, if you really intended to record new samples – you won’t record them unless you do!
P.S. Thanks to the The electro-music.com forum group, especially mi_dach, and also Yahoo Casio SK group, especially Plutoniq9, for help in this design. You guys are legends!!!
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Last edited by gmeredith on Thu Aug 03, 2006 6:22 pm; edited 3 times in total