18 Questions
How can a digital enabled GPIO pin on NodeMCU/ESP8266 be configured when set as an input?
Internal pull-up or pull-down
Which UART interface on NodeMCU/ESP8266 provides asynchronous communication at up to 4.5 Mbps?
UART0
What is the main function of UART1 (TXD1 pin) on NodeMCU/ESP8266?
Data transmit signal
How many UART interfaces are available on NodeMCU/ESP8266 for communication purposes?
2
What is the maximum communication speed supported by UART0 on NodeMCU/ESP8266?
4.5 Mbps
Which ADC precision is embedded in the NodeMCU for analog to digital conversion?
10-bit
How many PWM pins are available on the NodeMCU?
4
Which pin is used for SDIO on the NodeMCU?
D5
How many SPI pins are there on the NodeMCU?
4
Which pin is used for UART RX on the NodeMCU?
D2
How many ADC channels are present in the NodeMCU?
3
Which pin on the NodeMCU can be used for both SPI and I2C interfaces?
D8
What is the supported frequency range for Pulse Width Modulation (PWM) on NodeMCU/ESP8266?
100 Hz to 1 kHz
Which pins are used to reset the ESP8266 chip among the control pins on NodeMCU/ESP8266?
Reset pin (RST)
How many channels of Pulse Width Modulation (PWM) are available on NodeMCU/ESP8266?
4 channels
What is the maximum clock frequency supported by the SDIO interface on NodeMCU/ESP8266?
50 MHz
Which SPI feature allows for timing modes in the SPI format transfer?
4 timing modes
What is the purpose of the Chip Enable pin (EN) among the control pins on NodeMCU/ESP8266?
Enable the ESP8266 chip
Study Notes
NodeMCU/ESP8266 Features
- GPIO Pins: 17 pins can be assigned to functions such as I2C, I2S, UART, PWM, IR Remote Control, LED Light, and Button programmatically.
- GPIO configurability: internal pull-up or pull-down, high impedance, edge-trigger or level-trigger to generate CPU interrupts.
ADC Channel
- NodeMCU embedded with a 10-bit precision SAR ADC.
- Two functions can be implemented using ADC: testing power supply voltage of VDD3P3 pin and testing input voltage of TOUT pin.
UART Pins
- Two UART interfaces (UART0 and UART1) for asynchronous communication (RS232 and RS485).
- UART0: provides communication with TXD0, RXD0, RST0, and CTS0 pins.
- UART1: only data transmit signal, usually used for printing log.
SPI Pins
- NodeMCU/ESP8266 features two SPIs (SPI and HSPI) in slave and master modes.
- Supports 4 timing modes, up to 80 MHz, and divided clocks of 80 MHz, and up to 64-Byte FIFO.
SDIO Pins
- Secure Digital Input/Output Interface (SDIO) for directly interfacing SD cards.
- Supports 4-bit 25 MHz SDIO v1.1 and 4-bit 50 MHz SDIO v2.0.
PWM Pins
- 4 channels of Pulse Width Modulation (PWM) for driving digital motors and LEDs.
- PWM frequency range: 1000 μs to 10000 μs (100 Hz to 1 kHz).
Control Pins
- Chip Enable pin (EN): enables the ESP8266 chip when pulled HIGH, works at minimum power when pulled LOW.
- Reset pin (RST): resets the ESP8266 chip.
- Wake pin: wakes the chip from deep-sleep.
Power Pins
- VIN pin: can supply the NodeMCU/ESP8266 and its peripherals directly.
- Three 3.3V pins: output of the onboard voltage regulator, can be used to supply power to external components.
- GND pins: ground pins of NodeMCU/ESP8266.
I2C Pins
- Can connect I2C sensors and peripherals, both I2C Master and I2C Slave are supported.
- I2C interface functionality: can be realized programmatically, with a maximum clock frequency of 100 kHz.
Learn about the importance of setting the I2C clock frequency higher than the slave device's frequency, and how the GPIO pins on NodeMCU/ESP8266 can be utilized for functions like I2C, I2S, UART, and more. Explore configuring GPIO pins for internal pull-up or pull-down, setting them to high impedance, and generating CPU interrupts.
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