ComputerVoltageSources

Comments inline.

--- In ComputerVoltageSources@yahoogroups.com, Eric Brombaugh <ebrombaugh@...>
wrote:

>
> What's the hardware architecture going to be? I
> haven't ever seen a PSIM up close, but here's what I
> think is baseline:
>
> * BasicATOM Pro 28-M
> http://www.basicmicro.com/Product.aspx?productID=151&CategoryID=2
> - Up to 8 channels 10-bit Analog inputs
> - Serial digital I/O
> - parallel digital I/O.
> All shared on 20 GPIO pins.

For $10 more adds 4 more port pins and 32K of EEPROM.

>
> * 4-channels serially loaded DAC.
> What brand of DAC was used on the PSIM?
> 2 Dual DACs or one Quad DAC?
> Separate or simultaneous load strobe?
> How many bits?

Lack of port pins keeps it to a serial interface. The AD8420 is the original to the DAC7714
and requires no software change. The DAC7714 is only available in surface mount where
the DAC8420 is available in DIP or SM. The DAC8420 is $44 single piece. Probably put a
dual footprint on the board for DIP or SM.

http://www.analog.com/en/prod/0%2C2877%2CDAC8420%2C00.html

All 4 input channels can be read and all 4 output channels updated in 1.2 millisecond.
Plenty fast for CV generation.

>
> * Analog Signal conditioning.
> - Input gain & offset pots or fixed?

Both plus 1 volt per octave in calibrated.

> - Output gain & offset pots or fixed?

Fixed at 10.625 volts full scale. 4 steps per semitone at one volt per octave 12 bit.

> - Lowpass filtering?

Haven't seen a need for it so far.

>
> * Serial I/O
> - BasicATOM Pro uses built-in UART on H8/3664
> processor for firmware loads.
> - Need to re-task serial I/O for MIDI interfaces

There is a hardware serial interface TXD and RXD you can hang MIDI hardware on. Done
and tested.

Don't forget a DIN synch interface for the XOX boxes.

> - Front panel switch to select MIDI mode?
> Do we want a built in USB-Serial interface?
> - Many (most?) modern PCs now come without RS-232
> interfaces, but a USB-Serial chip is fairly cheap
> and readily available. See the SiLabs CP210x:
> http://www.silabs.com/tgwWebApp/public/web_content/products/Microcontrollers/

Interface/en/interface.htm

You completely lost me there. MBasic doesn't support USB (that I know of). Those without
RS232 will need to get USB to Serial cable.

>
> * Digital I/O
> - Digital I/O is somewhat scarce on the 28-pin
> BasicATOM Pro. Use 74HC595 serial-parallel for
> dedicated outputs, or Maxim MAX6957 port extender
> for flexible I/O over SPI.

Seems reasonable.

>
> * LCD
> - 2x16 char LCD w/ backlight seems a fairly useful
> & common mod. Use Serial I/O with
> external processor, or hook up parallel via SPI
> port extender (see above).

There is a good question. Dave seems to have a design already. If he volunteers it, it could
go into copper on PC board.

> * Buttons
> - Used for run/stop/etc.
> - Use dedicated GPIO pins on BasicATOM Pro, or
> hook up via SPI port extender using available
> interrupt line.
>

Certainly keep the Run/Stop with external gated OR logic and Run/Stop LEDs.