Transcript Introduction to MSP430

Introduction to MSP430G2553 and
MPU6050
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Outline
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Key Features
CPU Introduction
Interrupt
I/O
Clock
Timer
ADC
USCI
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Key features
 Ultralow-power architecture extends battery life
– 0.1 μA RAM retention
– 0.8 μA real-time clock mode
– 250 μA/MIPS active
 16-bit RISC CPU enables new applications at a fraction of the code size.
– Large register file eliminates working file bottleneck
– Compact core design reduces power consumption and cost
– Optimized for modern high-level programming
– Only 27 core instructions and seven addressing modes
– Extensive vectored-interrupt capability
 In-system programmable Flash(16KB) permits flexible code changes, field
upgrades and data logging.
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MSP430 Architecture
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CPU Introduction
• RISC architecture with 27 instructions and 7
addressing modes.
• Full register access including program counter,
status registers, and stack pointer.
• Single-cycle register operations.
• Large 16-bit register file reduces fetches to
memory.
• 16-bit address bus allows direct access and
branching throughout entire memory range.
• 16-bit data bus allows direct manipulation of
word-wide arguments.
• Constant generator provides six most used
immediate values and reduces code size.
• Direct memory-to-memory transfers without
intermediate register holding.
• Word and byte addressing and instruction
formats.
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27 Core RISC Instructions
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3 Instruction Formats
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CPU Operating modes
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Interrupt
 Are events applied to the application program that force a detour
in program flow;
 Cause CPU subprogram execution (ISR);
 When Interrupt Service Routine (ISR) ends, the program flow
returns to the previous state.
 There are three classes of interrupts:
 Reset.
 Interrupts not maskable by GIE which cannot be disabled by
the general interrupt enable bit (GIE), but are enabled by
individual interrupt enable bits (NMIIE, ACCVIE, OFIE). Used
for high priority events.
 Interrupts maskable by GIE where peripherals with interrupt
capability or the watchdog timer overflow in interval timer
mode, etc. Can be switched off by software.
The interrupt latency is the time between the event beginning and
the ISR execution; Normally needs 6 cycles
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Interrupt vector
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#pragma vector = TIMER0_A0_VECTOR
__interrupt void TA0_ISR(void)
{
__bic_SR_register_on_exit(CPUOFF);
}
// Exit LPM0
#pragma vector = USCIAB0TX_VECTOR
__interrupt void USCIAB0TX_ISR(void)
{
UCB0TXBUF = (UCB0RXBUF << 4) | 0x0f;
// Move RX data to TX
__bic_SR_register_on_exit(CPUOFF);
// Exit LPM0
}
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Clock
• ACLK: Auxiliary clock. ACLK is divided by 1, 2, 4, or 8 and is
software selectable for individual peripheral modules.
• MCLK: Master clock. MCLK is divided by 1, 2, 4, or 8 and is
used by the CPU and system.
• SMCLK: Sub-main clock. SMCLK is divided by 1, 2, 4, or 8 and
is software selectable for individual peripheral modules.
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Digital I/O Introduction
MSP430G2553 has 2 ports (P1 and P2), each port has up to eight I/O
pins (P1.0—P1.7, P2.0-P2.5). Every I/O pin is individually configurable
for input or output direction, and each I/O line can be individually read or
written to.
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Independently programmable individual I/Os
Any combination of input or output
Individually configurable P1 and P2 interrupts
Independent input and output data registers
Individually configurable pullup or pulldown resistors
• Direction Registers PxDIR (P1DIR=0x01)
• Input Register PxIN
• Output Registers PxOUT
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Timer
WDT is 16-bit timer that can be
used as a watchdog or as an
interval timer. WDT module
performs a controlled system
restart after a software problem
occurs(Four software-selectable
time intervals).
WDT Control register is password
protected and is Powers-up
active.
WDTCTL = WDTPW + WDTHOLD;
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Timer_A
Timer_A is a 16-bit timer/counter with three capture/compare registers
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Asynchronous 16-bit timer/counter with four operating modes
Selectable and configurable clock source
Two or three configurable capture/compare registers
Configurable outputs with PWM capability
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Timer control register(TACTL)
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ADC
The ADC10 module supports fast, 10-bit analog-to-digital conversions.
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200-kbps maximum conversion rate
Sample-and-hold with programmable sample periods
Conversion initiation by software or Timer_A
Software selectable on-chip reference voltage generation (1.5 V or 2.5 V)
Software selectable internal or external reference
Up to eight external input channels
Selectable conversion clock source
Single-channel, repeated single-channel, sequence, and repeated
sequence conversion modes
• ADC core and reference voltage can be powered down separately
• Data transfer controller for automatic storage of conversion results
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ADC operation steps
Here are the steps you must take to perform an A/D operation:
• Define the port pins that will be used as analog input channels. (INCHx)
• Select a clock source for the conversion operation, or set up the Watchdog
timer.(ADC10SSELx)
• Select a conversion mode (e.g., continuous, one-time conversion, etc).
(CONSEQx)
• Select the reference voltage VREF. (SREFx)
• Select the sample-and-hold time for the conversion. (ADC10SHTx)
• Enable the corresponding chosen pin for analog input.
• Switch ON the ADC functionality. (ADC10ON)
• Enable ADC (take a reading)
• Read the value after conversion; set a program variable to the reading.
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Example
ADC10CTL1 = INCH_3 + CONSEQ_1; // A3/A2/A1, single sequence
ADC10CTL0 = ADC10ON + ADC10IE; // ADC10ON, interrupt enabled
ADC10AE0 |= 0x0E;
// P1.1,2,3 ADC option select
ADC10CTL0 |= ENC + ADC10SC;
// Sampling and conversion start
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USCI I2C Mode
Figure : I2C Bus Connection
Diagram
The two pull up resistor is necessary for I2C mode to work properly
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I2C Module Operating Modes
Transmitter
Master
Receiver
I2C
Transmitter
Slave
Receiver
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I2C data transfer
Figure : I2C Module Data Transfer
The first byte after a START condition consists of a 7-bit slave address and the
R/W bit. When R/W = 0, the master transmits data to a slave. When R/W = 1,
the master receives data from a slave. The ACK bit is sent from the receiver
after each byte on the 9th SCL clock.
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I2C initialization code
void Init_i2c(uint8_t devAddr)
{
UCB0CTL1 |= UCSWRST; // Enable SW reset
UCB0CTL0 = UCMST + UCMODE_3 + UCSYNC; // I2C Master, synchronous mode
UCB0CTL1 = UCSSEL_2 + UCSWRST; // Use SMCLK, keep SW reset
UCB0BR0 = 10; // fSCL = 1Mhz/10 = ~100kHz
UCB0BR1 = 0;
P1SEL = BIT6 + BIT7; // Assign I2C pins to USCI_B0
P1SEL2 = BIT6 + BIT7; // Assign I2C pins to USCI_B0
UCB0I2CSA = devAddr; // Slave Address is 069h
UCB0CTL1 &= ~UCSWRST; // **Initialize USCI state machine**
IE2 |= UCB0RXIE + UCB0TXIE; // Enable RX and TX interrupt
}
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USCI UART Mode
In asynchronous mode, the USCI_Ax modules connect the MSP430
to an external system via two external pins, UCAxRXD and UCAxTXD.
UART mode is selected when the UCSYNC bit is cleared.
In UART mode, the USCI transmits and receives characters at a bit
rate asynchronous to another device. Timing for each character is
based on the selected baud rate of the USCI. The transmit and
receive functions use the same baud rate frequency.
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UART initialization code
void initUart(void)
{
UCA0CTL1 |= UCSSEL_2;
UCA0BR0 = 104;
UCA0BR1 = 0;
UCA0MCTL = UCBRS0;
P1SEL = BIT1 + BIT2 ;
P1SEL2 = BIT1 + BIT2 ;
UCA0CTL1 &= ~UCSWRST;
IE2 |= UCA0TXIE;
}
// Use SMCLK
// 1MHz 9600
// 1MHz 9600
// Modulation UCBRSx = 1
// P1.1 = RXD, P1.2=TXD
// P1.1 = RXD, P1.2=TXD
// **Initialize USCI state machine**
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USCI SPI Mode
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SPI mode features include:
7-bit or 8-bit data length
3-pin and 4-pin SPI operation
Master or slave modes
Independent transmit and receive shift registers
Separate transmit and receive buffer registers
Selectable UCLK polarity and phase control
Programmable UCLK frequency in master mode
Independent interrupt capability for receive and transmit
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USCI SPI Mode
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SPI example code
P1SEL = BIT1 + BIT2 + BIT4;
P1SEL2 = BIT1 + BIT2 + BIT4;
UCA0CTL0 |= UCCKPL + UCMSB + UCMST + UCSYNC;
UCA0CTL1 |= UCSSEL_2;
UCA0BR0 |= 0x02;
UCA0BR1 = 0;
UCA0CTL1 &= ~UCSWRST;
IE2 |= UCA0RXIE;
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MPU6050
 MPU6050: Gyroscope + Accelerometer
 ±2g, ±4g, ±8g and ±16g
 ±250, ±500, ±1000, and ±2000°/sec
 VCC and GND for power supply:3-5v
 SCL and SDA for I2C communication with MSP430
 XCL and XDA to connect magnetic sensor
Reference : MSP430 x2xx user guide
MPU6050 datasheet and register file
Where to buy
MSP430G2 $9.99
https://estore.ti.com/MSP-EXP430G2-MSP430-LaunchPadValue-Line-Development-kit-P2031.aspx
MPU6050 $5.75
http://www.ebay.com/itm/MPU-6050-3-Axis-AccelerometerSensor-Gyroscope-6DOF-Module-3-3V-5V-For-Arduino/161108492494?pt=LH_DefaultDomain_0&hash=item2582d0
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