Tinkering TI MSP430F5529

USB Module Overview

The USB module of MSP430F5529 is not very difficult to use. TI has provided some working deploy-able examples in their 430ware software suite. However, some explanation is needed at first to get started. We will go through two basic USB module examples – USB CDC and USB HID.

In simple terms, USB CDC is a USB mode with which we can emulate virtual serial COM ports and USB HID is another common USB mode with which we can make devices like USB keyboard, mouse, input devices, printer, scanner, etc as well as other similar I/O devices. MSP430F5529 also supports mass storage class. In all cases, we create a way to make our MSP430 micro communicate with a host device.

Now let’s see what we need to get started with USB coding. Apart from driverlib files and personal libraries we will need additional libraries for USB software development. Note the following folders:

  • USB API Folder
  • USB_app Folder
  • USB_config Folder

Apart from these we’ll need some important files too:

  • Hal header and source files
  • system_pre_init source file

Fortunately for us we don’t have to change anything in these files/folders. We just have to add them in our USB projects and the process of adding doesn’t need any special attention. Alternatively, we can simply copy example USB projects from MSP430ware and have them customized as per need.

Very briefly speaking, USB API folder, sub-folders and files in them are what describe a specific USB mode’s working. They list relevant functions for a given mode. USB_app folder and associated files further elaborate these operations. USB devices need descriptors and USB_config folder and files contain them. Hal source and header files contain clock and GPIO setups and system_pre_init basically contains nothing except watchdog setup.

Shown below is the folder tree of a typical USB project. All I stated so far is what boils down to this folder tree.

In the main, all of the aforementioned files are included as shown below:

#include "driverlib.h"

#include "USB_config/descriptors.h"
#include "USB_API/USB_Common/device.h"
#include "USB_API/USB_Common/usb.h"
#include "USB_API/USB_CDC_API/UsbCdc.h"
#include "USB_app/usbConstructs.h"

#include "hal.h"

Pay attention to these functions shown below:

USB_setup(TRUE, TRUE);

Clock setting is very important because USB hardware is clock sensitive. FLL is used for both MCLK and USB clock. It is also necessary to set the right level for PMM core. Usually level 2 is preferred as the clock speed is 8MHz. On start-up, all GPIO ports are driven low to avoid floating input and unwanted EMI-related issues. This causes some additional power consumption. Thus, it is recommended to setup GPIOs for other tasks after initial USB port initialization. Please refer to TI’s official docs for additional info.

If you are not using official TI boards or equivalents and designing stuffs on your own then pay attention to USB hardware design considerations. EMC considerations are also needed to focused more alongside good PCB layout practices.

In addition to these, we can develop our own customized PC/mobile applications with Visual C Sharp (C#), Visual Basic or some other similar computer programming languages. This part is beyond the scope of this tutorial and won’t be discussed.

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