Convenient microcontrollers for PI project wanted.

[Aziz]

As Carl mentioned, it is more convenient to use a transistor and using the full voltage on Ugs. By pre-biasing the gate to the MOSFET, a faster switching can be obtained.
On the fiber optics there are very fast optocoupler available today, which can also solve the level shifting very elegant.

But I haven't decided which one I will use. It depends on the power supply solution and it will be definitely without any switching DC/DC converters to eliminate additional noise.

[Aziz]

Hi Aziz,

Do a google on ATXmega, they will be available Q4 2008. Some nice goodies like 12 bit ADC, 12 bit DAC, 32MHz clock speed, DMA etc.

regards
bugwhiskers

Hi bugwhiskers,

http://www.elab-pascal.de/downloads/DOCs/XMEGA_A4.pdf

This is getting very interesting. The internal 12-bit ADC is capable of 2 MSPS. Perhaps a true digital Boxcar-Averager can be realized in a PI!
I am observing this for the future use.

Kindly regards,
Aziz

[bugwhiskers]

Many micro's I/O pins go open circuit whilst programming is in progress. With the 2 transistor method the mosfet will be turned on whilst programming or if something else happens that doesn't pull the PNP base low. I neglected to mention that the "balance" resistors shown in the pic aren't required. By using a comparator and pullup or pulldown resistors you have full control over what happens to the mosfet gate drive.

regards
bugwhiskers

[bugwhiskers]

Hi bugwhiskers,

http://www.elab-pascal.de/downloads/DOCs/XMEGA_A4.pdf

This is getting very interesting. The internal 12-bit ADC is capable of 2 MSPS. Perhaps a true digital Boxcar-Averager can be realized in a PI!
I am observing this for the future use.

Kindly regards,
Aziz

Notice too that the ADC reference can be an internal 1 volt. This makes for a 1 count resolution of 244 uV (1/4096). Many 16 bit ADC's have a 2.56 volt reference making their 1 count resolution 39uV(2.56/65535).

regards
bugwhiskers

[Aziz]

The ATxmega chips are designed for low voltage operation: 1.8 .. 3.6 V. This is probably the reason for 1.00 V ADC reference.
Anyway, 12 bit of dynamic range should be enough. With the Boxcar averager, we can gain more bits and dynamic range.
To use lock-in amplifier for PI is quite difficult or senseless but the boxcar averager could be implemented easily.

Boxcar averager will be the next breakthrough on PI technology!!!

[Aziz]

Hi Friends,

my first AVR µC test board is ready and working. I tested this with a simple flash LED light test through the port B bits (counting from 0 to 255 and again with some delay).
See attached picture for the test board.

Aziz