Nice.. looks good so far. Will be interesting to see your hardware.
Just curious... will you have detents on your drawbars/faders?
I don't know if that's still a thing but I believe some organs did as I recall playing with a home-style Hammond organ from '50s or '60s and my recollection is detent settings to call up the 'recipes' from a sounds book.
BTW - You got me wondering about the merits of SPI vs I2C; found an interesting reference:
http://www.byteparadigm.com/applicat...spi-protocols/
AREF is an input for the voltage from an extenal reference voltage for the ADCs.
Didn't notice the comment and didn't spot it when I looked it over.
AREF is an input for the voltage from an extenal reference voltage for the ADCs.
Another little question.
In my schematics I've put a 4.7k Ohm resistor between both the 2 i2c lines and 3.3v as suggested in the Wire reference page, but this post seems to suggest that 4.7k is more adeguate for 5V while for 3.3v 2.2K Ohm is better.
I'm really not sure I understood that post, maybe it's a whole different situation, so any hint is well appreciated
4.7K is the standard resistor used for 5v systems. It will run on 3.3v volt systems, but you might not be able to set the i2c speed to faster speeds. If you never set the i2c faster than 100Khz, then it probably does not matter for small i2c setups with only a few devices and short wires.
From what I've read of other posts over the years (I'm a software guy, not an EE) the default value to use for 3.3v is 2.2K. If Paul or Nox771 say otherwise, follow their advice, and ignore mine, since they are the i2c experts. I started using 2.2K over 4.7K for i2c, when Paul released the Prop Shields, and those had 2.2K resistors in them.
In general, you only want one set of resistors on the i2c bus. If you are hooking up devices with their own set of resistors, you might not want to add additional resistors (for example, as I mentioned, the prop shields have 2.2k resistors built-in).
In complcated i2c setups, this document is one of the ones to consult to calculate the best resistors to use: http://www.ti.com.cn/cn/lit/an/slva689/slva689.pdf.
This post shows the effect of varying i2c resistance: http://www.dsscircuits.com/articles/47-effects-of-varying-i2c-pull-up-resistors.
Another little question.
In my schematics I've put a 4.7k Ohm resistor between both the 2 i2c lines and 3.3v as suggested in the Wire reference page, but this post seems to suggest that 4.7k is more adeguate for 5V while for 3.3v 2.2K Ohm is better.
I'm really not sure I understood that post, maybe it's a whole different situation, so any hint is well appreciated
Presumably Paul has found 4.7K still works at the lower voltage in most cases or the wire page would offer different values.Texas Instruments said:Once the minimum and maximum value of the pullup resistor has been selected, the decision for the value
of resistor can be made based on trade-off between the speed and power budget. A smaller resistor will
give a higher speed because of smaller RC delay, and a larger resistor will give lower power consumption.