AN169

Rev. 2.3

3

3.

Host API Functions

The host API is provided in the form of a Windows Dynamic Link Library (DLL). The host interface DLL

communicates with the USB device via the provided device driver and the operating system's USB stack. The

following is a list of the host API functions available:

SI_GetNumDevices()

- Returns the number of devices connected

SI_GetProductString()

- Returns a descriptor for a device

SI_Open()

- Opens a device and returns a handle

SI_Close()

- Cancels pending IO and closes a device

SI_Read()

- Reads a block of data from a device

SI_Write()

- Writes a block of data to a device

SI_CancelIo()

- Cancels outstanding overlapped IO

SI_FlushBuffers()

- Flushes the TX and RX buffers for a device

SI_SetTimeouts()

- Sets read and write block timeouts

SI_GetTimeouts ()

- Gets read and write block timeouts

SI_CheckRXQueue()

- Returns the number of bytes in a device's RX queue

SI_SetBaudRate()

- Sets the specified CP210x Baud Rate

SI_SetBaudDivisor()

- Sets the specified CP210x Baud Divisor Value

SI_SetLineControl()

- Sets the CP210x device Line Control

SI_SetFlowControl()

- Sets the CP210x device Flow Control

SI_GetModemStatus()

- Gets the CP210x device Modem Status

SI_SetBreak()

- Sets the Break State for CP210x device.

SI_ReadLatch()

- Gets the port latch value from a CP2103 device

SI_WriteLatch()

- Sets the port latch value to a CP2103 device

SI_GetPartNumber()

- Gets the CP210x device part number

SI_DeviceIOControl()

- Allows sending low-level commands to the device driver

SI_GetDLLVersion()

- Gets the version of the DLL currently in use

SI_GetDriverVersion()

- Gets the version of the USBXpress driver

In general, the user initiates communication with the target USB device(s) by making a call to SI_GetNumDevices.

This call will return the number of target devices. This number is then used as a range when calling

SI_GetProductString to build a list of device serial numbers or product description strings.

To access a device, it must first be opened by a call to SI_Open using an index determined from the call to

SI_GetNumDevices. The SI_Open function will return a handle to the device that is used in all subsequent

accesses. Data I/O is performed using the SI_Write and SI_Read functions. When I/O operations are complete, the

device is closed by a call to SI_Close.

Additional functions are provided to flush the transmit and receive buffers (SI_FlushBuffers), set receive and

transmit timeouts (SI_SetTimeouts), check the receive buffer's status (SI_CheckRXQueue), and miscellaneous

device control (SI_DeviceIOControl).

For CP210x devices, functions are available to set the baud rate (SI_SetBaudRate); set the baud divisor

(SI_SetBaudDivisior); adjust the line control settings such as word length, stop bits, and parity (SI_SetLineControl);

set hardware handshaking, software handshaking, and modem control signals (SI_SetFlowControl); and get modem

status (SI_GetModemStatus). Additional functions are available for CP2103/4/5/8 devices to get (SI_ReadLatch) and

set (SI_WriteLatch) the values of the additional GPIO pins available on the device. In order to differentiate between

CP210x devices, a function (SI_GetPartNumber) has been provided to return the part number.

Each of these functions are described in detail in the following sections. Type definitions and constants are defined

in "Appendix D—Definitions from C++ header file SiUSBXp.h”.