Progetti - PIC

 

28-40pin UniBoard

 


 

Description.

Uniboard is scheduled for all PIC mid-range and enhanced at 28 and 40 pin, as 16F870, 16F876, 16F876, 18F2321, 18F22K46 and the like.
You can also use chip family pakage 10F in 8-pin DIP.

 

Uniboard has been designed to be used to "package" with a power supply stand alone battery, which together form a completely autonomous and free of any connections with the network.

This, apart from the intrinsic safety, allows to have ready the entire support structure of a wide range of processors, but not replicated every time, in a completely simple and usable on any workstation.

The circuit is the minimum that is around the chip: Uniboard is ultra simple, but complete as basis for testing and developing embedded microcontrollers, do not need anything else.

The card is of limited size (147 x 67 mm or so), but it contains everything you need to run the PIC:

  • double socket to 28 and 40-pin DIP chip package
  • power outlets and decoupling capacitors
  • circuit with reset button and a wide range of options
  • clock circuit with various options
  • connector ICSP / ICD
  • plug connectors for the I / O
  • set of 8 low power LEDs for displays and test on-board
  • dedicated connector for serial communications, with status LED
  • potentiometer for analog references
  • area components: large breadboard area for easy addition of components
  • option for external module for the oscillator Timer1
  • test point for the connection of instruments (oscilloscope, multimeter, etc.)

The scheme is gathered in this single image:

A particular observation concerns the sign indicating a removable pin to insert, if required, a particular component.

This is due to the following consideration: an embedded can operate with a very large amount of options; the weld tab to a certain quartz or a certain value of resistance limits the possibilities of experimentation. The capacity of pins in which the components can be inserted when and where needed allows both the 'immediate interchangeability of these components, is the possibility to extend to the greatest degree experimentation.

In any case, it is possible very well do without this system and stick to a more conventional method of salda-se-serve/dissalda if not needed; enough that the printed circuit board, such as that created and visible in the images, is of excellent quality .

Let's see in detail the various sections.


 

Power supply.

The classic Vdd / Vss came with a two pin connector 2.54 (like all other external connections), but polarized to avoid the 'inversion.

This means that you need an external power supply-stabilizer.
This choice was made based on specific considerations.

Firstly, the board is open to every kind of application and devices of any type can be connected to its I / O. 
So an on-board power supply, due to available space could be limited in the amount of current supplied.

Secondly, the PIC can operate in a very wide range of voltages, from 2 to 5.5 V. A power supply on-borad, to allow for sufficient flexibility of experimentation, would have to also be variable.

It is therefore preferred a different technique: the 'power supply is external and therefore leaves maximum freedom to user to choose what you prefer or is better suited to application.

In any case, the project Uniboard provides for the availability of power supplies of the same size as the board, powered by rechargeable batteries and can be connected mechanically to the same to form a single block completely independent from any other connection.

 

A power supply "Uniboard format."

It is a step-up switch, capable of delivering over 300 mA.

Are selectable voltages of 5V and 3.3V, in addition to a range variable between 2.7 and 5V, adjustable with a trimmer multiturn, useful, for example, to verify the operation to 3.6V or 4.8V.

Power is supplied by two NiCd or alkaline batteries.

 

A more economical and efficient foresees the connection with the power module UBS-12, which has higher performance (more current, more output plugs, diemnsioni reduced, etc..).

Obviously, using Uniboard with debug tools as Pickit, You can give power to the connected to the ICSP / ICD, within the limits of the current supplied by these tools, an external power supply and the superfluous for an extremely wide range of circuits and applications.

The power, then, is distributed to the board with a good number of decoupling capacitors and is available in each block of pin connections with the I / O outside.

In the picture, the set of connections to PORTB and PORTD, interspersed with a pin from which you can draw the 'power to attached devices.

This allows you to create a wide range of external modules, the LED display, LCD and graphics, the real clock, buttons, contacts, relays, analog, etc.., Easy to connect and directly fed by Uniboard.
Beside each group of pins, the printed circuit board provides
a double line of holes, connected to the corresponding pin I / O, useful for the addition of other connectors or components on board, further increasing the expandability and accessibility.


 

 

 

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Aggiornato il 10/11/12.