Datasheet

UniPi
5-12V Step-up (internal 12V power supply)
All inputs are primarily set to be driven by the internal 12V power supply. The 12V line is wired out
via the orange connector marked as 12V. Do not exceed 200ma current draw.
Jumper settings
In case of using external power source, inputs must be configured by JP2 - JP5 jumpers. The
configuration must be done before powering up the UniPi. Using the external power supply and
proper jumper configuration provides galvanic isolation for its inputs.
Jumper configuration when using external power source:
• JP2
o Switching this jumper to the side of the JP2 label causes the P02 (green connector) to
act as an input for ground from the external power source. Otherwise P02 is
connected to the internal 12V.
o This step must be done as first when changing jumper settings.
o Please note that after this step, the GND of UniPi is connected to P02! Make sure to
proceed with JP3 settings after this step.
• JP3
o When switched to the side of the JP3 label, inputs I01 and I02 act as inputs for signal
from the connected peripheral device via the external power source.
o The ground of power supply for this inputs must be connected to the P02.
o Please note that to set I01 and I02 for ext. power source make sure to switch JP2 first
and then JP3, after that you can safely connect the peripheral device.
• JP4
o When switched to the side of the JP4 label, inputs I03 and I04 act as inputs for signal
from the connected peripherals via the external power source.
o The ground of power supply for this inputs must be connected to P01.
• JP5
o When switched to the side of the JP5 label, inputs I05 - I14 act as inputs for signal
from the connected peripherals via the external power source.
o The ground of power supply for this inputs must be connected to P01.
o Please note that I13 and I14 are wired out via the P5 header of Raspberry Pi (models
before the PLUS versions).
Analog Inputs
UniPi features two analog 0-10V input channels (via the MCP3422, address 0x68) marked as AI1 and
AI2. Each channel has its own + and – (e.g. AI1+ and AI1-). The + connector expects positive voltage
from the connected device and – expects the negative pole (the GND). The guaranteed accuracy is
5% however 1% is commonly reachable.
To correctly calculate the input voltage, a coefficient of the resistor divider has to be taken into
account. The coefficient of each channel is saved in EEPROM as single precision binary floating point
format binary32 (IEEE 754). Before version 1.1 the coefficient is not saved in the EEPROM and thus
must be calculated during conversion in software (Typically the value is around 5.56). See chapter
EEPROM for more details.
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