Arduino – SOMO interfacing:

• Hooked up the SOMO with a 220uf capacitor on the power supply going to ground and put one 2.2k resistor between the arduino pin and the SOMO pin for each of the serial wires.
• First memory card(PNY) was not compatible.  Needed to get a sandisk 2gb uSD.
• At first i had the speaker hooked up directly to the SOMO.  This produced good sound but had far less range with only 7 steps.  Once I knew this was working I put the output wire through our amplifier.
• The piezoelectric speaker that i had from my computer motherboard is really only designed for tones so it might be blown.
• Eventually I am going to have the i2c resistor controlled through the arduino instead of the FTDI chip we are using.  I am not sure how often this will happen but there was a conflict with the com ports.
• Spent a good amount of time trying to find the best speaker for the job.  Eventually I found these: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=668-1206-1-ND
• 13mmx13mmx4mm is a good size for fingertips and we probably embed them into the surface of the next prototype(if that is not insanely hard to do).  They get up to 85db which is about the same as someone singing loudly so that should be good.  Not sure how much it resonates, but we can probably increase that through mounting techniques.
• Tomorrow, I will start working on the rcs system code to prepare it to work with our original prototype so we can test this method.  A lot of its already written, just have to add the SOMO commands and fix the parts that I couldn’t test before.  We can probably use our big cone speaker while we wait for the fingertip sized ones.

Aurdino – SOMO 14D interfacing:

• Serial communication is a bit more difficult then I thought it would be because the SOMO does not follow any standard protocol.  Instead you have to time the clock cycles and data timings manually.  Luckily someone has translated the 4D Systems sample code to work with the arduino:  http://forum.sparkfun.com/viewtopic.php?f=14&t=21388
• The code doesn’t do exactly what I want but the main important part is the sendData(int) function:

1. void sendData(int ThisSong)  //it says this song but it can be any 16 bit command
2. {
3. int TheSong = ThisSong;
4. int ClockCounter=0;
5. int ClockCycle=15;//0x0f;
6. digitalWrite(pinClock,HIGH); // Hold (idle) for 300msec to prepare data start
7. delay(300);
8. digitalWrite(pinClock,LOW); //Hold for 2msec to signal data start
9. delay(2); //2msec delay
10. while(ClockCounter <= ClockCycle)
11. { digitalWrite(pinClock,LOW);
12. if (TheSong & 0x8000)
13. {digitalWrite(pinData,HIGH);
14. }
15. else
16. {digitalWrite(pinData,LOW)
17. }
18. TheSong = TheSong << 1;
19. delayMicroseconds(200); //Clock cycle period is 200 uSec – LOW
20. digitalWrite(pinClock,HIGH);
21. ClockCounter++;
22. delayMicroseconds(200); //Clock cycle period is 200 uSec – HIGH
23. }
24. digitalWrite(pinData,LOW);
25. digitalWrite(pinClock,HIGH); // Place clock high to signal end of data
26. }

• Considering there may be a time I will not have the code given to me, its best to explain whats going on here so that I know how to do this with just data sheet timings.

1. Lines 3-5 set up are pretty basic.  Declare a counter, declare a maximum, pass the parameter into the function.
2. Lines 6-7 set the clock to high for 300ms to ensure a data reset between consecutive commands
3. Lines 8-9 a two ms low tells the SOMO that the data stream will begin.
4. lines 10-23 is the while loop.  16 cycles for the 16 bits of data
5. line 11 sets the clock to low between bits.  The first run its already low so it doesn’t really matter but it doesn’t hurt to set it to low again
6. lines 12-17 was really confusing to me at first.   I am used to only using Boolean operations within if statements.  & is a bit wise function comparison function.  Instead of checking the whole thing to see if its the same it checks each bit and only produces a 1 when both are 1 and 1.  Every other combination produces a 0.  So by comparing the command to 1000000000000000(0x8000) you will only get a non-zero value(true) if the leftmost bit is a 1.  If its true it sends a high and false sends a low.
7. line 18 bit shifts left to test the next leftmost bit during the next cycle
8. lines 19-22 I am not sure why this has a 400us delay.  The total cycle period is supposed to be 200us,  high should be 100us, and low should be 100us.  I guess as long as its consistent and under 1ms it will work.  The two delays are in place to ensure the clock cycle takes at least 400us(it should be 200us).
9. lines 24-25 are just used to set the idle state.  A high on the clock line lasting more then 2ms stops that data transmission.  The data line doesn’t have to be set low during idle but why not.

• The 300ms delay(+20ms processing after command is received) between commands is a bit long.  Our amplifiers are much quicker(100ns per pulse cycle*steps) so this shouldn’t hurt response time too much except on initial contact.  I believe when you send the command for select track and it will auto play but if you have to do two commands to do this that would be over a half second delay…  I can probably minimize this by having a delta t function which measures the time between commands and delays the difference if its under 300ms.

Arduino – SOMO interfacing:

• Got a basic melody to play on the arduino by following this tutorial:  http://arduino.cc/en/Tutorial/Tone

• Was originally going to communicate with the SOMO 14D by using the push-button operations using the digital outs of the arduino because it only has one serial port.  There were a few problems with this approach.

1. Takes many digital outputs to control one SOMO
2. Cannot easily switch between tracks which are not right next to each other
3. Hard to control active-low switches without the use of a gate

• The solution is of course to use serial.  But one port is not enough for even a 2 finger prototype.  Lucky there is a way to make the other digital ports act like serial ports using the SoftwareSerial library.  An example of how this can be done is found here:  http://arduino.cc/en/Tutorial/SimpleSoftwareSerial
• Was not sure if the regulated 3.3 volt port on the arduino would work for the SOMO.  Found out it puts out 50ma and the SOMO’s peak consumption is 45ma.  This should work for one but we will probably need a 3.3v voltage regulator for any others.  Sparkfun(http://www.sparkfun.com/products/526) sells them so we can get them when we get the other SOMOs.  The ones sparkfun sells can output up to 800ma so one would be all we need to power all the SOMOs.  I think a decoupling capacitor on the power input protects the circuit from receiving too many amps.  The wiki article was a bit confusing on this matter.  I will read it a bit more in depth and ask Clift if I can’t figure it out.
• An interesting article on unregulated power supplies: http://www.sparkfun.com/tutorials/103
• Formatted uSD to have 16-bit fat file system.  Also changed some music files to .ad4 and copied them to the uSD.
• Should be ready to wire up the SOMO tomorrow.  The SOMO data sheet is poorly organized which has held me back a little bit.  I do not want to fry the thing out of carelessness.  Hopefully our memory card works, its not on the definitely doesn’t work list so that is good.

MISC:

• You can now scan to email with the printer.  The e-mail portion wasn’t working before because they changed the server after we moved here.  Now instead of using mail.fgm.com:25 we use spam.fgm.com:25.  This is the only easy way to scan documents for Windows 7 machines which do not have the HP Solution center software yet.