User Manual

FIFO Modes

FIFO is an acronym for First In, First Out. It used to buffer data to help with flow of communication to

devices.

There are 32 slots of FIFO data, for each of the three output channels: yaw, pitch, and roll (X,Y,Z). Each

slot has 16 bits of data.

The great thing about having a FIFO is the host processor does not need to continuously poll data from

the sensor. Instead, it can wake up only when needed and burst the significant data out from the FIFO.

This buffer can work in five different modes.

There are five FIFO mode settings available; the default mode is “Bypass mode.” To see how to access

different modes, see FIFO_CTRL_REG and FIFO_SRC_REG in the datasheet posted to the 27911 product

page at www.parallax.com.

Bypass Mode

In bypass mode, the FIFO is not operational and for this reason it remains empty.

FIFO Mode

In FIFO mode, data from the yaw, pitch, and roll channels are stored in the FIFO.

Stream Mode

In stream mode, data from yaw, pitch, and roll measurements are stored in the FIFO. The FIFO

continues filling until full (32 slots of 16-bit data for yaw, pitch, and roll). When full, the FIFO discards the

older data as the new data arrives.

Bypass-to-stream Mode

In bypass-to-stream mode, the FIFO starts operating in bypass mode, and once a trigger event occurs,

the FIFO starts operating in stream mode.

Stream-to-FIFO Mode

In stream-to-FIFO mode, data from yaw, pitch, and roll measurements are stored in the

FIFO. An interrupt can be enabled on pin INT2, setting the I2_WTM bit in CTRL_REG3, which is triggered

when the FIFO is filled to the level specified in the WTM. The FIFO continues filling until full (32 slots of

16-bit data for yaw, pitch, and roll).

Example Code

Example code is available for download from the 27911 product page at www.parallax.com

BASIC Stamp 2

The L3G4200D_Gyroscope_Demo.bs2 program reads raw X,Y,Z values from the Gyroscope module using

the default I²C interface, and displays the values in the BASIC Stamp Editor’s Debug Terminal. The

software is a free download from www.parallax.com/basicstampsoftware.

Propeller™ P8X32A

The L3G4200D_example_code.spin program reads raw X,Y,Z values from the Gyroscope module using

the default I²C interface, and displays the values in a serial terminal. It calls FullDuplexSerial.spin, a

library object of the Propeller Tool software, which is available from www.parallax.com/Propeller.