Entradas digitales - Hardware¶
Nota
This section covers digital input hardware. For a software guide to digital inputs, see Entradas digitales - Software.
A digital signal is a signal that can be in one of several discrete states. In the vast majority of cases, the signal is the voltage in a wire, and there are only two states for a digital signal - high, or low (also denoted 1 and 0, or true and false, respectively).
The Systemcore’s built-in Smart Input/Output ports (or «Smart I/O») ports function on 3.3V, so «high» corresponds to a signal of 3.3V, and «low» to a signal of 0V [1].
Connecting to the Systemcore Smart I/O ports¶
Advertencia
Consulte siempre las especificaciones técnicas del sensor que está utilizando antes de cablear el sensor, para asegurarse de que se está conectando el cable correcto a cada pin. Si no lo hace, puede dañar el dispositivo.
Advertencia
Never directly connect the power pin to the ground pin on any port on the Systemcore! This will trigger protection features on the Systemcore and may result in unexpected behavior.
The Systemcore has 6 Smart I/O ports (numbered 0-5), as seen in the image above. Each port has three pins - signal, power («3.3V»), and ground («gnd»). The «power» and «ground» pins are used to power the peripheral sensors that connect to the analog input ports - there is a constant 3.3V potential difference between the «power» and the «ground» pins [2]. The signal pin is the pin on which the signal is actually measured.
All Smart I/O ports have built-in «pull-down» resistors between the power pins and the signal pins - these ensure that when the signal pin is «floating» (i.e. is not connected to any circuit), they consistently remain in a «low» state.
Advertencia
The roboRIO had pull-up resistors instead of pull-down resistors, so the behavior of the Smart I/O ports is different from that of the roboRIO’s digital input ports. This means that sensors designed for the roboRIO’s digital input ports may have different wiring for the Smart I/O ports.
Conexión de un conmutador simple a un puerto DIO¶
The simplest device that can be connected to a DIO port is a switch (such as a limit switch). When a switch is connected correctly to a DIO port, the port will read «low» when the circuit is open, and «high» when the circuit is closed.
A simple switch does not need to be powered, and thus only has two wires. Switches should be wired between the signal and the power pins of the DIO port. When the switch circuit is open, the signal pin will float, and the pull-down resistor will ensure that it reads «low.» When the switch circuit is closed, it will connect directly to the power rail, and thus read «high».
Por hacer
Update above image to use the Systemcore Smart I/O ports and wiring for pull-down resistors.
Conectando un sensor energizado a un puerto DIO¶
Muchos sensores digitales (como la mayoría de los interruptores de proximidad sin contacto) requieren energía para funcionar. Un sensor energizado generalmente tendrá tres cables - señal, poder y tierra. Estos deben estar conectados a los pines correspondientes del puerto DIO.
Por hacer
Update above image to use the Systemcore Smart I/O ports.
Advertencia
The roboRIO provided 5V power to the «power» pin of its DIO ports, whereas the Systemcore provides 3.3V. Sensors designed for the roboRIO’s DIO ports may not work correctly when connected to the Systemcore’s Smart I/O ports. Please consult with the sensor datasheet to ensure it can run from 3.3V.
Conexión de un sensor que utiliza varios puertos DIO¶
Algunos sensores ( así como quadrature encoders) es posible que deba conectarse a varios puertos DIO para funcionar. En general, estos sensores solo requerirán un solo poder y un solo pin de tierra - solo se necesitará el pin de señal de los puerto(s) adicionales.
Por hacer
Update above image to use the Systemcore Smart I/O ports.