Serial port API

API Overview

The calling sequence is open>set_baudrate>read/write>fulsh_io>close

open

int esp_open(char* pDeviceName)

Open the serial port by the specified device name. This operation should be used before other operations.

Parameters

pDeviceName

The alias for serial port. Available values: in W1/W1V2 DB9: works for DB9 port at the back side of the terminal. GS0_Q1: works for USB host port at the right side of terminal to connect with Q1 via USB cable in master mode. in Q1 3g WIZARHANDQ1: works for USB serial port in slave mode. Q1_USB_SERIAL or USB_SERIAL: works for USB serial port in master mode. SERIAL_EXT: works for internal fiscal module. in Q1 4g and Q2 series USB_SLAVE_SERIAL: works for USB serial port in slave mode. USB_HOST_SERIAL or USB_SERIAL: works for USB serial port in master mode. SERIAL_EXT: works for internal fiscal module.

Returns
int	The result code, >= 0, handle of this device; <0 error code.

close

int esp_close(int nHandle)

Close the serial port opened before. The open and close API are pair operations. If you don’t want to use this device, you should call the close API to release this device.

Parameters
nHandle	int: Handle of this device, returned from open

Returns
int	The result code, >= 0, success; <0 error code.

set_baudrate

int esp_set_baudrate(int nHandle, unsigned int nBaudrate)

Set the baud rate of the serial port so that this device can read and write in the same baud rate. This API should be used before read and write.

Parameters
nHandle	int: Handle of this device, returned from open
nBaudrate	int: Baud rate

Returns
int	The result code, >= 0, success; <0 error code.

read

int esp_read(int nHandle, unsigned char* pDataBuffer, int nExpectedDataLength, int nTimeout_MS)

Get information from the serial port.

Parameters
nHandle	int: Handle of this device, returned from open
pDataBuffer	unsigned char*: Data buffer
nExpectedDataLength	int: Data length to read
nTimeout_MS	int: Time in milliseconds. 0 : read and return immediately; <0: read until got data.

Returns
int	The result code, >= 0, success, the data length of read; <0 error code.

write

int esp_write(int nHandle, unsigned char* pDataBuffer, int nDataLength)

Send information from the serial port.

Parameters
nHandle	int: Handle of this device, returned from open
pDataBuffer	unsigned char*: Data buffer
nDataLength	int: Data length

Returns
int	The result code, >= 0, data length of written; <0 error code.

flush_io

int esp_flush_io(int nHandle)

Flush the IO buffer of the serial port.

Parameters
nHandle	int: Handle of this device, returned from open

Returns
int	The result code, >= 0, written data length; <0 error code.