M-G362 Datasheet, PDF (29/69 Pages) Epson Company – IMU (Inertial Measurement Unit)

6. Digital Interface
This device has the following two external interfaces.
(1)
SPI interface
(2)
UART interface
The SPI interface and the UART interface have almost the same functions, except additionally the
UART interface supports Auto Mode function. Because both interfaces are always active, the user
needs only to connect the desired interface pins SPI or UART, without needing any hardware pin
configuration or selection.
NOTE: Connecting both SPI and UART at the same time is not supported and may result in malfunction
of the device.
The registers inside the device are accessed via the SPI or UART interfaces.
In this document, data sent to the device is called “Command” and data sent back in response to the
command is called “Response”. There are two types of commands: write command and read command.
The write command has no response. The write command always writes to the internal register in 8-bit
words. The response to the read command, i.e. the data from the internal register, is always read in
16-bit words.
When reading from the registers, there is a special mode called the burst mode in addition to the normal
mode.
When the IMU output data rate is high (i.e. 1000sps and 2000sps), it is possible to exceed the
bandwidth of the host interface and cause the data transmission to be incorrect. In this case, the user
must balance the transmission data rate and the bandwidth capability of the host interface.
Adjust the following settings accordingly to optimize the host interface bandwidth:
• For the UART, adjust the baud rate in BAUD_RATE (UART_CTRL [0x08(W1)] bit [9:8]).
• For the SPI, adjust the host side SPI clock frequency and SPI wait time.
Adjust the following settings accordingly to optimize the transmission data rate:
• The transmission data rate is affected by the data output rate setting in DOUT_RATE
(SMPL_CTRL [0x04(W1)] bits [15:8]).
• The transmission data rate is also affected by the number of output bytes included in burst
mode read transfer. The adjustment to the number of output bytes is in registers
BURST_CTRL1 [0x0C(W1)] and BURST_CTRL2 [0x0E(W1)].
Several concrete examples for setting the transmission data rate and host interface bandwidth are
shown below:
(1) For UART and 32-bit output:
• BAUD_RATE =“11" of UART_CTRL [0x08(W1)] bit [9:8]: 460800 baud
• DOUT_RATE = 0x02 of SMPL_CTRL [0x04(W1)] bit [15:8]: 1000Sps
• BURST_CTRL1 [0x0C(W1)] = 0xF006: FLAG, TEMP, angle rate, acceleration, GPIO, and COUNT output
• BURST_CTRL2 [0x0E(W1)] = 0x7000: TEMP, angle rate, and acceleration output are 32-bit.
In the above case, a data output rate of 1000Sps is supported, but 2000Sps is not.
(2) For SPI and 32-bit output:
• SPI Interface Transmission Setting: FSCLK=1MHz and tSTALL=24us for normal mode
• DOUT_RATE = 0x02 of SMPL_CTRL [0x04(W1)] bit [15:8]: 1000Sps
• BURST_CTRL1 [0x0C(W1)] = 0xF006: FLAG, TEMP, angle rate, acceleration, GPIO, and COUNT output
• BURST_CTRL2 [0x0E(W1)] = 0x7000: All TEMP, angle rate, and acceleration output are 32-bit.
In the above case, a data output rate of 1000Sps is supported, but 2000Sps is not.
(3) For UART and 16-bit output:
• BAUD_RATE =“11" of UART_CTRL [0x08(W1)] bit [9:8]: 460800 baud
• DOUT_RATE = 0x01 of SMPL_CTRL [0x04(W1)] bit [15:8]: 2000Sps
• BURST_CTRL1 [0x0C(W1)] = 0xF006: FLAG, TEMP, angle rate, acceleration, GPIO, and COUNT output
M-G362PDC1 Data Sheet
Seiko Epson Corporation
25
Rev.20131217