The following table describes the functions of the signals on a QUUB dockable.
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Pin
|
Name
|
Description
|
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1
|
TX0
|
UART0 transmit. Also connected to the debugging header.
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|
2
|
RX0
|
UART0 receive input. Also connected to the debugging header. If used by the debugger then it should not be used by any dockables on the main PCB as they don't have access to the #DBG signal which can be used to tristate this signal.
|
|
3
|
TX1
|
Connected directly to the MCU's UART1 transmit output (pin 11).
|
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4
|
RX1
|
Connected directly to the MCU's UART1 receive input (pin 12).
|
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5
|
SCL0
|
The I2C0 channel's clock signal. Connected directly to the MCU (pin 7) but also has an active pullup device to increase the allowable bus capacitance, and therefore the usable lenght of the I2C bus. Also connected to the QUUBlink and PiicoDEV/STEMMA-QT/QWIIC busses.
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|
6
|
SDA0
|
The I2C0 channel's data signal. As SCL0 but connected to MCU pin 6.
|
|
7
|
ADC
|
Connected indirectly via an analogue MUX to the MCU's ADC0 input (pin 31). This MUX also connects all the seven dockable ADC signals and the SENSE stackplane signal.
|
|
8, 9, 18, 19
|
DIOx
|
General-purpose digital IO signals. These are connected to an IO expander IC and are under application program control. Can be set to inputs or output in any combination.
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|
10
|
#SHDN
|
This signal can be used to shut a dockable down, for example to save power or maybe restart a dockable that is not responding to the #RST signal. This is common to all dockables and therefore if used must be OR'd with the #SEL signal.
|
|
11
|
GND
|
The system GND or 0V power signal.
|
|
12
|
VBAT
|
A power signal sourced by a backup battery if one is installed on the system.
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|
13
|
12V
|
This is an unregulated 12V power signal to be used for devices that need more power and/or a higher voltage, say an alram horn. The 12V value is nominal as typically it would be connected to a battery that is undergoing charge/discharge cycles so the voltage may vary considerably, from about 11V to over 14V.
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|
14
|
5V0
|
A regulated 5V0 power signal. Only available at a full 5V if a PSU module provides it as such, if the system is running from the USB cable conected to the Pico this will be 5V minus one diode drop.
|
|
15
|
3V3
|
A regulated 3V3 power signal. If no other PSU modules are installed and the system is running from the USB cable plugged into the Pico then this connects indirectly to pin 36 on the Pico through a perfect diode and an analogue switch. This switch is under program control plus it will automatically shut the power down if the current draw exceeds 500mA. This scenariio will also cause a #FAULT assertion.
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16
|
#FAULT
|
Any non-masked fault signals that get asserted will assert this signal. It can also be asserted by hardware on a debugging attachment. If this signal is asserted by any source it will shut down the 3V3 power to the stackplane and most of the hardware on the QUUB board. Some critical hardware will remain powered in this situation.
This is an input to a dockable, if a dockable needs to generate a fault output it should use the #MFTL (see below) signal.
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17
|
#MFLT
|
A fault signal for the dockable. This signal is connected to the fault handler which in turn will generate the system #FAULT signal if the fault is not masked.
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|
20
|
MISO
|
The system SPI input signal. All modules (IE docakables and stackables) on the system that use this signal MUST hi-Z their output if not selected. SPI is also connected to the debugging header.
|
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21
|
MOSI
|
The system SPI output signal.
|
|
22
|
CLK
|
The system SPI clock signal.
|
|
23
|
#INT
|
The doackable's interrupt output. These are unique to each dockable.
|
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24
|
#EEP
|
A select signal for the dockable's onboard configuration EEPROM. This is common to all dockables and therefore if used must be OR'd with the #SEL signal.
|
|
25
|
#RST
|
This signal can be used to reset the hardware on the dockable. This is common to all dockables and therefore if used must be OR'd with the #SEL signal.
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26
|
#SEL
|
A unique select signal for each dockable.
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