This application note will show how to connect the RPI-Hub-Module to the Raspberry Pi and install FTDI drivers to control the module. The application note will then explain how the module may be used to read values from an external ADC device over the SPI interface.
1 Introduction
The Raspberry Pi is a single board computer (SBC) based on an ARM processor aimed at teaching young people about computers and programming. FTDI have developed an expansion module for this Raspberry Pi based on the FT2232H, the RPI-Hub-Module. This application note explains how to use the RPI-Hub- Module as an SPI master to read an external ADC. Schematics and sample code will be provided. 1.1 Overview
The Raspberry Pi is a single board computer primarily running Linux OS. The board has a number of IO ports for developing applications with, including 2 USB host ports. With the RPI-Hub-Module connected to the Raspberry Pi USB port, FTDI can demonstrate using an FTDI chipset operating on an ARM processor running Linux to expand the IO options of the Raspberry Pi while also offering buffered protection to the processor from badly connected external peripherals.
The RPI-Hub-Module is a FT2232H based design allowing for
2 independent interfaces which may be configured for GPIO, UART, FIFO, I2C or SPI etc. The module also includes a USB hub creating an additional 2 USB host ports. More information on the hub can be found here.
Figure 1.1 RPI-Hub-Module
More information on the Raspberry Pi can be found here.
1.2 Scope
This application note assumes the user has already created a working Linux image on an SD card and the Raspberry Pi is already functional.
This application note will show how to connect the RPI-Hub-Module to the Raspberry Pi and install FTDI drivers to control the module. The application note will then explain how the module may be used to read values from an external ADC device over the SPI interface.
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I would recommend a small RF choke, something around 22uHs in the 5V line to the ADC and opamps. Something like http://www.cs80.com/ADC22uh.jpg –Crow