The USB-ISS Multifunction USB Communications Module provides a complete interface between your PC and the I2C bus, SPI bus, a Serial port and general purpose Analogue Input or Digital I/O. The module is powered from the USB. Operating voltage is selectable between 3.3v and 5v. and can supply up to 80mA at 5v for external circuitry from a standard 100mA USB port.
Support I2C at 100khz
Support I2C at fixed 20, 50, 100, 400 & 1000khz
I2C + I/O
SPI Mode at 24khz to 3Mhz
Serial Mode at 300baud to 3Mbaud
I2C Direct – Used to build custom I2C sequences
Bootloader for user updates – Uses Microchip Bootloader
Supply power to external Circuit – Up to 80mA for USB-ISS
5v operation & 3.3v operation
Mounting holes on PCB
- This documentation is divided up into 6 pages.
- This page describes the connections to the USB-ISS, the USB driver installation and setting of the USB-ISS operating modes.
- Five further pages describe the operational commands and the Boot-Loader.
- I2C Operation, describes all the I2C commands available
- SPI Operation, describes the format for SPI communication
- Serial Operation, describes how to send and receive serial data.
- I/O Operation, describes how to set pins high/low and read digital or analogue inputs.
- Boot Loader, describes how to update the firmware in the USB-ISS.
First Step – Get The Drivers
Before connecting the USB-ISS module, you should download the driver and unzip it to a temporary folder. Now connect the USB-ISS module and navigate windows to the temporary folder and install the driver. The USB-ISS will now appear as a COM port.
Which COM port?
After installing the drivers, and plugging in the USB-ISS module to a spare USB port, you will want to know which COM port it has been assigned to. This will vary from system to system depending on how many COM ports you currently have installed. To find out where it is, right click on your “My Computer” desktop icon and select “Properties->Hardware->Device Manager”. Now scroll down and open the “Ports (COM & LPT)” tab. You should see the USB serial port listed – COM5 in the example below. If you want to change the COM port number – just right click on it, select properties, select advanced and select the COM port number from the available list. The COM port default will probably be set up for 9600 baud, 8 data bits, no parity and one stop bits, but what ever it is just ignore it. These settings are not actually used because we have a full 12Mbits USB connection right into the heart of the processor.
The diagram below shows the connections for the various modes.
|Power Link – Remove for 3.3v operation.
3.3v or 5v
Add the link for 5v, remove it for 3.3v
The processor on the USB-ISS is equally happy running from 3.3v or from 5v. With the LEDs it takes up to 20mA so when 5v is selected by linking the power select pins, the USB-ISS module can supply up to 80mA to external devices. When the link is removed a 3.3v regulator supplies the power. This regulator is capable of 50mA, so when running at 3.3v up to 30mA is available to your circuits. If your application requires more than this, or has its own supply, then leave the 3.3v/5v pin unconnected. Do not apply your own voltage to this pin.
Each I/O pin, 1 to 4, may be individually selected to be Analogue Input or Digital Input or Digital Output.
Inputs will not accept voltage higher than the supply, so when operating at 3.3v the inputs are NOT 5v tolerant.
Analogue inputs span from 0v to the supply for a range of 0-1023 (10-bit A/D conversion).
SCL and SDA
These pins are the I2C bus connections. They should be connected directly to the SCL and SDA pins on your I2C device. The USB-ISS module is always a bus master, and is fitted with 4.7k pull-up resistors on the PCB. These resistors are automatically disconnected in other modes.
SDI, SCK, SDO and CE
SDI is the SPI input to the USB-ISS, connect it to SDO on your device.
SDO is the SPI output from the USB-ISS, connect it to SDI on your device.
SCK is the SPI clock output from the USB-ISS, connect it to SCK on your device.
CE is the active low chip enable signal, connect it to CE on your device.
Tx and Rx
These are logic level signals, not RS232. Do not connect this to an RS232 port without using a suitable RS232 logic level inverter chip.
The 0v Ground pin must be connected to the 0v (Ground) on your device.
For more information , please refer here