10/12 BIT BUFFER/ISOLATOR WITH ARDUINO ZERO
The schematic diagrams for the UNO and the ZERO are identical with the exception of the Micro to Optocoupler connections (which can be easily changed, being simply wired to the screw terminals of the shield) and of the I2C, which now have dedicated pins, as shown in the schematic below and discussed in the next post. For a techical description of the schematc, see BUFFER/ISOLATORS FOR DrDAQ/2012/2016 DATALOGGERS PART 2 at:
The schematic diagram for the new ZERO Buffer/Isolator is enclosed below.
One obvious, but not previously mentioned point, is that to have exact numerical correspondence between PWM and D.C. value, the reference voltage and the peak of the PWM square-wave must have an identical value. This is the reason why the Micro reference and the voltage feed to the optocouplers must have the identica value of 2.5V.
Another important point regards System Resolution.
- With Arduino UNO the System Resolution is limited by the Resolution of the output pins PWM which CANNOT exceed 8 Bit (255 levels), while the Resolution of the Input pins is fixed @ 10 Bit (1023 levels).
- With Arduino ZERO the System Resolution is limited by the Resolution of the input pins, which CANNOT exceed 12 Bit, while the Resolution of the output pins PWM can go easily up to 16 Bit, by manipulation of the PER parameter.
The Micro sketch is also uploaded in this post. It is an "universal" sketch in the sense that, apart from EXTERNAL REFERENCE, several INTERNAL REFERENCES can be programmed by simply removing stops to the necessary script. All the Reference voltages mentioned in previous Part 3 can be programmed. As an example, both the sketch for EXTERNAL REFERENCE and the one for INTERNAL 1V have been uploaded, with the differing entries shown in green colour.
Operational PC Picts will be posted next.