DIGILENT PmodGYRO 3-Axis Gyroscope User Manual
- June 12, 2024
- DIGILENT
Table of Contents
DIGILENT PmodGYRO 3-Axis Gyroscope
Product Information
The PmodGYRO is a 3-axis gyroscope powered by the STMicroelectronics L3G4200D. It is designed to provide motion sensing data on each of the three Cartesian axes. The module can be configured to report angular momentum at a resolution of up to 2000 dps (degrees per second) at an output rate of up to 800Hz. It features a 3-axis MEMS digital gyroscope with high shock survivability and user-selectable resolution (250/500/2000dps).
Product Usage Instructions
To interface with the PmodGYRO, you can use either SPI or I2C communication protocols. The module communicates with the ST L3G4200D gyroscope chip to retrieve motion sensing data.
Interfacing with the Pmod
The PmodGYRO has two headers, J1 and J2, which provide the pinout for connection. The pinout description table is as follows:
| Header | Pin | Signal | Description |
|---|---|---|---|
| J1 | 1 | ~CS | Chip Select |
| 2 | MOSI | Master-Out-Slave-In | |
| 3 | MISO | Master-In-Slave-Out | |
| 4 | SCLK | Serial Clock | |
| 5 | GND | Power Supply Ground | |
| 6 | VCC | Positive Power Supply (3.3V) | |
| J2 | 1, 5 | SCL | Serial Clock |
| 2, 6 | SDA | Serial Data | |
| 3, 7 | GND | Power Supply Ground | |
| 4, 8 | VCC | Positive Power Supply (3.3V) |
Note: Any external power applied to the PmodGYRO must be within the range of 2.4V and 3.6V, although it is recommended to operate the Pmod at 3.3V.
Data Retrieval
The measured data from the gyroscope is recorded and stored in the registers of the L3G4200D in degrees per second (dps). A measured value of 360 dps is equivalent to 60 rpm. You can retrieve the data from the PmodGYRO by following the provided code example in the user manual.
Overview
The PmodGYRO is a 3-axis gyroscope powered by the STMicroelectronics L3G4200D. By communicating with the chip through SPI or I2C, users may configure the module to report angular momentum at a resolution of up to 2000 dps at an output rate up to 800Hz.
Features include:
- 3-axis MEMS digital gyroscope with high shock survivability
- Get angular momentum data with user selectable resolution (250/500/2000dps)
- Two customizable interrupt pins
- User configurable signal filtering
- Power-down and Sleep modes
- Small PCB size for flexible designs 1.0 in × 0.8 in (2.5 cm × 2.0 cm)
- 12-pin Pmod port with SPI interface and additional I²C interface
- Library and example code available in resource center
Functional Description
The PmodGYRO utilizes ST L3G4200D gyroscope to provide motion sensing data on each of the three Cartesian axes. Users may configure both the resolution and filtering options for the measured data.
Interfacing with the Pmod
The PmodGYRO communicates with the host board via the SPI or I²C protocols. By
driving the Chip Select (CS) line to a logic low voltage state, SPI mode is
enabled. The first byte sent over SPI informs the on-board chip if a read or
write command is going to be issued, if the register address should be
incremented after a particular command has been completed, and the 5 bit
address of the register that is to be written to.
An example timing diagram for SPI read and writes from the L3G4200D datasheet
is provided below:
Figure 1. Timing diagram.
Correspondingly, if the CS line is left at a high voltage state by an internal
pull-up resistor, the I²C mode of the PmodGYRO is enabled. The on-board chip
has two possible slave address in the form of 110100x where x is the voltage
state of the Master-In-Slave-Out (MISO) pin on the SPI header. After the slave
address and the read or write bit has been transmitted and the message was
acknowledged, a 7-bit register address can then be transmitted. The most
significant bit (the first bit of the 8-bit of the transfer) indicates if
multiple bytes of information are to be transferred.
An example transfer scheme for a master device reading multiple bytes of data
from the PmodGYRO is provided below:
| Master | Slave |
|---|---|
| Start |
Slave address and
Write bit
|
| ACK
Multi-byte bit and
register address
|
| ACK
Restart|
Slave address and read
bit
|
| ACK
| Data
ACK|
| Data
ACK|
| Data
NACK|
Stop|
Table 1. Example transfer scheme.
Data is recorded and stored within the registers of the L3G4200D in degrees
per second (dps). Correspondingly, a measured value of 360 dps is equivalent
to 60 rpm. Users can retrieve data from the PmodGYRO by following the provided
code example.
Pinout Description Table
Header J1
Pin| Signal| Description| Pin| Signal| Description
1| ~CS| Chip Select| 7| INT1| Interrupt 1
2| MOSI| Master-Out-Slave-
In
| 8| INT2| Interrupt 2
3| MISO| Master-In-Slave-
Out
| 9| (NC)| Not Connected
4| SCLK| Serial Clock| 10| (NC)| Not Connected
5| GND| Power Supply
Ground
| 11| GND| Power Supply
Ground
6| VCC| Positive Power
Supply (3.3V)
| 12| VCC| Positive Power
Supply (3.3V)
Header J2
Pin| Signal| Description
1,
5
| SCL| Serial Clock
2,
6
| SDA| Serial Data
3,
7
| GND| Power Supply
Ground
4,
8
| VCC| Positive Power
Supply (3.3V)
| |
| |
Table 2. Pinout description table.
Any external power applied to the PmodGYRO must be within 2.4V and 3.6V;
however, it is recommended that Pmod is operated at 3.3V.
Physical Dimensions
The pins on the pin header are spaced 100 mil apart. The PCB is 1 inch long on the sides parallel to the pins on the pin header and 0.8 inches long on the sides perpendicular to the pin header.
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