DIGILENT PmodGYRO Peripheral Module Instruction Manual

: June 16, 2024
: DIGILENT

Table of Contents

Overview
Functional Description
SPI Communication
References
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PmodGYRO™
Reference Manual
Revision: August 3, 2011
Note: This document applies to Rev. A of the board.

DIGILENT PmodGYRO Peripheral Module

Overview

The PmodGYRO is a peripheral module featuring the STMicroelectronics® L3G4200D MEMS motion sensor. The L3G4200D provides a three-axis digital output gyroscope with built in temperature sensor.

Features include:

Standard SPI and I2C™ interface
250/500/2000dps Selectable Resolutions
Two customizable interrupt pins
Power-down and Sleep Mode
User configurable signal filtering

Functional Description

The PmodGYRO uses a standard 12-pin connection and communicates via SPI or I²C, defaulting to I²C communication. A pull-up resistor on the CS line keeps the device in I²C mode unless the CS line is driven low by the master device

Interface
When communicating with the device the master must provide a register address and a flag specifying whether the subsequent action is a read or write. The actual transfer of data follows this command. Through this method, the user can either configure the device by writing to specific control registers within the device, or read back data from separate readonly registers.

Two interrupts directly map to pins available to the user on connector J1 of the PmodGYRO. The configuration of INT1, present on pin 7 of J1, is entirely user customizable. The main use of INT1 stems from high and low events on the three axes about which the gyroscope measures angular speed. By default, the INT1 is disabled. The second interrupt, INT2, is primarily used for data ready and FIFO interrupts and maps to pin 8 on J1.
For more information about the control registers, data collection, and interrupt settings available for user configuration, see the data sheet for the L3G4200D on the STMicroelectronics® website.

SPI Communication

The SPI interface uses three or four signal lines for communication depending on the current configuration of the device. These are Chip Select (CS), Serial Data In (SDI) or simply Serial Data (SDA) in 3-wire SPI mode, Serial Data Out (SDO), and Serial Clock (SCL). The PmodGYRO defaults to the 4-wire operating mode. In order to use the 3-wire mode, a control register must be written to. For more detailed SPI communication, refer to the device data sheet.

I²C Communication

The I²C standard uses two signal lines, I²C data (SDA) and serial clock (SCL). The device supports both standard, 100 kHz, and fast, 400 kHz, serial clocks. In accordance with I²C protocol, the L3G4200D has a devicespecific 7-bit address used by the serial master to communicate with multiple devices on a data bus. The device uses the address 110100xb, where pin 3 on J1 (SDO/SA0) defines the least-significant-bit (LSB). By default, the LSB of the address while be ‘1’ due to a pull-up resistor on JP1 as shown by the schematic available on the Digilent website. While the default value is ‘1’, by simply connecting pin 3 on J1 to the ground rail the user can change the LSB to a ‘0’. This user selectable bit enables two PmodGYROs to be used on the same I²C bus. The data sheet for the L3G4200D contains further device specific I²C information.

| Connector J1 — SPI Communications
---|---
Pin| Signal| Description
1| CS| Chip Select
2| SDA/SDI/ SDO| Serial Data In
3| SDO/SAO| Serial Data Out/LSB of I2C Device
Address
4| SCLJSPC| Serial Clock
5| GND| Power Supply Ground
6| VCC| Power Supply (3.3V)
7| INT1| Programmable Interrupt
8| INT2| Data Ready/FIFO Interrupt
9| NC| Not Connected
10| NC| Not Connected
11| GND| Power Supply Ground
12| VCC| Power Supply (3.3V)
Connector J2 — I2C Communication
Pin| Signal| Description
1 & 2| SCLJSPC| Serial Clock
3 & 4| SDA/SDI/ SDO| Serial Data
5 & 6| GND| Power Supply Ground
7 & 8| VCC| Power Supply (3.3V)