class SoftSPI – Software Implementation of SPI Bus Protocol

2023-08-31

This class provides bus protocol of Serial Peripheral Interface (SPI).

EC600E/EC800E module supports this feature.

Constructor

machine.SoftSPI

class machine.SoftSPI(gpio_clk, gpio_cs, gpio_mosi, [gpio_miso],[wire_type],[speed],[mode],[cs_active_lvl])

Parameter

  • gpio_clk - Integer type. The GPIO corresponding to the CLK.
  • gpio_cs - Integer type. The GPIO corresponding to the CS.
  • gpio_mosi - Integer type. The GPIO corresponding to the MOSI.
  • [gpio_miso] - Integer type. The GPIO corresponding to the MISO. For 3-wire SPI, this parameter can be omitted and the MOSI can be used for receiving and sending data.
  • [wire_type] - Integer type. Set SPI to 3-wire SPI or 4-wire SPI. WIRE_3: 3-wire SPI. WIRE_4: 4-wire SPI. Default value: 4-wire SPI.
  • [speed] - Integer type. Transmission speed. 0: 50 kHz. 1: 100 kHz. Default value: 100 kHz.
  • [mode] - Integer type. SPI mode. Range: 0–3. Default value: 0.
    0 : CPOL=0, CPHA=0
    1 : CPOL=0, CPHA=1
    2: CPOL=1, CPHA=0
    3: CPOL=1, CPHA=1
  • [cs_active_lvl] - Integer type. CS active level. LOW: low level. HIGH: high level. Default value: low level.

Return Value

The object created - Successful execution

Error - Failed execution

Example

from machine import SoftSPI
# Create a 4-wire SPI object. CLK: GPIO14. CS: GPIO11. MOSI: GPIO12. MISO: GPIO13. SPI mode: 0. Transmission speed: 100 kHz. CS: low level. 
spi=SoftSPI(gpio_clk=SoftSPI.GPIO14,gpio_cs=SoftSPI.GPIO11,gpio_mosi= SoftSPI.GPIO12,gpio_miso= SoftSPI.GPIO13)
# Create a 4-wire SPI object. CLK: GPIO14. CS: GPIO11. MOSI: GPIO12. MISO: GPIO13. SPI mode: 1. Transmission speed: 50 kHz. CS: high level. 
spi=SoftSPI(gpio_clk=SoftSPI.GPIO14,gpio_cs=SoftSPI.GPIO11,gpio_mosi=SoftSPI.GPIO12,gpio_miso=SoftSPI.GPIO13,
            speed=0,mode=1,cs_active_lvl=SoftSPI.HIGH)
# Create a 3-wire SPI object. CLK: GPIO14. CS: GPIO11. MOSI: GPIO12. SPI mode: 0. Transmission speed: 100 kHz. CS: low level. 
spi=SoftSPI(gpio_clk=SoftSPI.GPIO14,gpio_cs=SoftSPI.GPIO11,gpio_mosi= SoftSPI.GPIO12,wire_type= SoftSPI.WIRE_3)
# Create a 3-wire SPI object. CLK: GPIO14. CS: GPIO11. MOSI: GPIO12. SPI mode: 2. Transmission speed: 50 kHz. CS: high level.
spi=SoftSPI(gpio_clk=SoftSPI.GPIO14,gpio_cs=SoftSPI.GPIO11,gpio_mosi=SoftSPI.GPIO12,wire_type=SoftSPI.WIRE_3,
            speed=0,mode=2,cs_active_lvl=SoftSPI.HIGH)

Methods

SoftSPI.read

SoftSPI.read(recv_data, datalen)

This method reads data.

Parameter

  • recv_data - Bytearray type. An array used to receive data.
  • datalen - Integer type. Length of the data to be read.

Return Value

0

SoftSPI.write

SoftSPI.write(data, datalen)

This method writes data.

Parameter

  • data - Bytes type. Data to be written.
  • datalen - Integer type. Length of data to be written.

Return Value

0

SoftSPI.write_read

SoftSPI.write_read(r_data, data, datalen)

This method writes and reads data.

Parameter

  • r_data - Bytearray type. An array used to receive data.
  • data - Bytes type. Data to be sent.
  • datalen - Integer type. Length of data to be read.

Return Value

0

For 3-wire SPI, in the communicating process, MOSI is set to the output mode first and data will be sent. And then MOSI is set to the input mode and the datalen bytes of data will be read.

Example

Please use this method with the peripherals.

Example for 4-wire SPI

from machine import SoftSPI

spi=SoftSPI(gpio_clk=SoftSPI.GPIO14,gpio_cs=SoftSPI.GPIO11,gpio_mosi= SoftSPI.GPIO12,gpio_miso= SoftSPI.GPIO13)

if __name__ == '__main__':
    r_data = bytearray(5)  # Create a buffer for receiving data
    data = b"world"  # Test data
    spi.write_read(r_data, data, 5)  # Write and receive data
    spi.read(r_data,5) # Receive data to r_data
    spi.write(data,5)# Send data

Example for 3-wire SPI

from machine import SoftSPI

spi=SoftSPI(gpio_clk=SoftSPI.GPIO14,gpio_cs=SoftSPI.GPIO11,gpio_mosi= SoftSPI.GPIO12,wire_type= SoftSPI.WIRE_3)

if __name__ == '__main__':
    r_data = bytearray(5)  # Create a buffer for receiving data
    data = b"world"  # Test data
    spi.write_read(r_data, data, 5)  # Write and receive data
    spi.read(r_data,5) # Receive data to r_data
    spi.write(data,5)# Send data