More on MSP430 Programming

1
More on MSP430 Programming
2
Administration

• Week 17 (6/8) Term Project workshop
• No class, I will be here to help you work on your
  term project
• Deadline for the lab exercises
• Demo and turn on your codes before 2008/6/8 2359

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Outline

• More peripherals
• Watchdog Timer
• Supply Voltage Supervisor (SVS)
• Direct Memory Access (DMA)
• Flash Memory Controller
• External 8Mbit Flash Memory M25P80
• Temperature/humidity sensor SHT11
• Low Power Modes
• MSP430 Software Coding Techniques

4
Watchdog Timer

• Most embedded systems need to be self-reliant
• watchdog timer is a hardware
• that can watch for system hang
• reset the processor if any occur
• It is a counter
• counts down from some initial value to zero
• must select a counter value
• periodically restarts the counter
• before it counts to zero
• If it counts to zero
• trigger a system reset

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Watchdog timer on MSP430

• 16-bit timer, four software-selectable time
  intervals
• (clock source)/32768, (clock source)/8192, (clock
  source)/512, (clock source)/64
• Can be configured into watchdog mode or interval
  mode
• Watchdog mode generate a reset when timer
  expired
• Interval mode generate a interrupt when timer
  expired
• When power up, it is automatically configured in
  the watchdog mode
• Initial 32-ms reset interval using the DCOCLK.
• Must halt or setup the timer at the beginning

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Usage

• Stop watchdog timer
• WDTCTL WDTPW WDTHOLD
• Change watchdog timer interval
• WDTCTL WDTPWWDTCNTCL(interval)
• Periodically clear an active watchdog
• WDTCTL WDTPWWDTCNTCL

ClockSource/32768 ClockSource/8192
WDTIS0 ClockSource/512 WDTIS1 ClockSource/64
WDTIS0 WDTIS1
Password-protected must include the write
password
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Example
Select clock source ACLK
Select timer interval (clock source)/8192
32768Hz/8192 4Hz
Reset watchdog counter
Reset watchdog counter
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Supply Voltage Supervisor

• Monitor the AVCC supply voltage or an external
  voltage
• Can be configured to set a flag or generate a
  reset when the supply voltage or external voltage
  drops below a user-selected threshold
• Comparison
• 14 threshold levels for AVCC
• External input SVSIN
• compared to an internal level of approximately
  1.2 V

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SVS Register
This bit will set to 1 if the voltage is below
threshold

• SVSCTL
• VLDx

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Example
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Direct Memory Access

• Transfers data from one address to another,
  without CPU intervention
• Increase throughput and decrease power
  consumption
• DMA on MSP430
• Three independent transfer channels
• Configurable transfer trigger selections
• Timer, UART, SPI, ADC, ..
• Byte or word and mixed byte/word transfer
  capability
• Single, block, or burst-block transfer modes
• Block sizes up to 65535 bytes or words

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DMA Addressing Modes
Source/destination address can be configured to
be unchange/increment/decrement after each
transfer
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DMA Transfer Modes

• Six transfer modes
• Single transfer, block transfer, burst-block
  transfer, repeated single transfer, repeated
  block transfer, repeated burst-block transfer
• Single transfer
• Each transfer requires a separate trigger, DMA is
  disable after transfer
• Must re-enable DMA before receive another trigger
• Repeated single transfer DMA remains enable
• Another trigger start another transfer
• Block transfer
• Transfer of a complete block after one trigger,
  DMA is disable after transfer
• Repeated block transfer DMA remains enable,
• Another trigger start another transfer
• Burst-block transfer
• Block transfers with CPU activity interleaved,
• Repeated burst-block transfer DMA remains enable
• Keep transferring
• CPU executes at 20 capacity

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DMA Triggers
A transfer is triggered when the CCIFG flag is set
A transfer is triggered when USART0 receives new
data
A transfer is triggered when USART0 is ready to
transmit new data
A transfer is triggered by an ADC12IFGx flag.
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Initialization And Usage

• Example

(DMACTL0) Configure transfer trigger
(DMA0SA) Configure source address
(DMA0DA) Configure destination address
(DMACTL1) Select transfer mode, addressing mode,
and/or other setting, and enable DMA
(DMA0SZ) Configure block size
Use DMA to transfer a string to UART buffer, send
it out through UART
Repeated single transfer
Source address is incremented
source byte to destination byte
DMA enable
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Others About DMA

• DMA Transfer Cycle Time
• DMA transfers are not interruptible by system
  interrupts

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Flash Memory Controller

• MSP430 flash memory is bit-, byte-, and
  word-addressable and programmable
• Segment erase and mass erase
• Minimum VCC voltage during a flash write or erase
  operation is 2.7 V
• Program code are stored in the flash
• Unused flash memory can be use to store other data

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Flash Memory Characteristics

• Write in bit-, byte-, or word erase in segment
• MSP430F1611 segment size
• Information memory 128 bytes
• Main memory 512 bytes
• Erase
• Make every bit in the segment as logic 1
• Write
• Generate logic 0 in the memory
• Flash endurance
• Maximum erase/write cycles
• In MSP430 datasheet
• Minimum 10000 cycles
• Typical 100000 cycles

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Flash Memory Operation

• Read, write, erase mode
• Default mode is read mode
• Write/erase modes are selected with the BLKWRT,
  WRT, MERAS, and ERASE bits
• Flash Memory Timing Generator
• Sourced from ACLK, SMCLK, or MCLK
• Must be in the range from 257 kHz to 476 kHz
• Incorrect frequency may result in unpredictable
  write/erase operation

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Flash Memory Erase

• Example

(FCTL2) Setup timing generator
(FCTL3) Unlock flash memory
(FCTL1) Configure the operation
Disable all interrupts and watchdog
(FCTL3) lock flash memory
Re-enable interrupt and watchdog
Wait until erase complete
Dummy write
Password protected
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Flash Memory Write

• Example

(FCTL2) Setup timing generator
(FCTL3) Unlock flash memory
(FCTL1) Configure the operation
Disable all interrupts and watchdog
(FCTL3) lock flash memory
Re-enable interrupt and watchdog
Wait until write complete
Write to specific memory address
Password protected
22
Outline

• More peripherals
• Watchdog Timer
• Supply Voltage Supervisor (SVS)
• Direct Memory Access (DMA)
• Flash Memory Controller
• External 8Mbit Flash Memory M25P80
• Temperature/humidity sensor SHT11
• Low Power Modes
• MSP430 Software Coding Techniques

23
M25P80

• External Flash storage on Taroko
• 8 Mbit Flash Memory
• SPI Bus Compatible Serial Interface
• Memory organization
• 16 sectors
• Each sector containing 256 pages
• Each page is 256 bytes
• Operations
• Erase set all bit to 1
• Program(write) reset some bits to 0
• Read read the content of the flash

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Signals And Connections
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SPI

• MasterSlave mode
• Synchronous protocol
• All transmissions are referenced to a common
  clock
• Clock generated by the master (MCU)
• Four main signals
• Master Out Slave In (MOSI) data from master to
  slave
• Master In Slave Out (MISO) data from slave to
  master
• Serial Clock (SCLK or SCK) clock
• Chip Select (CS) select particular peripheral
  when multiple peripherals are connected to master

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Memory organization
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Instruction Set
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Operation

• Read Data Bytes (READ)
• Read data from memory
• Page Program
• Write bytes to a page
• Up to 256 bytes each time
• Sector Erase
• sets all bits to 1 inside the chosen sector
• Bulk Erase
• Erase (sets to 1) all memory data

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Device Driver

• Download here
• http//nslab.ee.ntu.edu.tw/courses/wsn-labs-spring
  -09/labs/m25p80Driver.rar
• Important functions in hal_m25p80.c
• void halM25p80Init(void)
• void m25p80PowerUp(void)
• void m25p80PowerDown(void)
• void m25p80PageWrite(UINT16 add, UINT8 buff,
  UINT8 size)
• void m25p80PageRead(UINT16 add, UINT8 buff,
  UINT8 size)
• void m25p80SectorErase(UINT8 add)
• void m25p80BulkErase(void)

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Functions

• void m25p80PageWrite(UINT16 add, UINT8 buff,
  UINT8 size)
• address range from 0x0000 to 0x0fff (4096 pages
  in total)
• At most 256 bytes
• Always write from the beginning of the page
• void m25p80PageRead(UINT16 add, UINT8 buff,
  UINT8 size)
• address range from 0x0000 to 0x0fff (4096 pages
  in total)
• At most 256 bytes
• Always read from the beginning of the page
• void m25p80SectorErase(UINT8 add)
• address range from 0x00 to 0x0f (16 sectors in
  total)
• Each sector is 65536 bytes

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Example
32
Outline

• More peripherals
• Watchdog Timer
• Supply Voltage Supervisor (SVS)
• Direct Memory Access (DMA)
• Flash Memory Controller
• External 8Mbit Flash Memory M25P80
• Temperature/humidity sensor SHT11
• Low Power Modes
• MSP430 Software Coding Techniques

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SHT11

• Relative humidity and temperature sensors
• Digital output
• Manufacturer defined interface
• two wires bi-direction

1. Use a GPIO pin as clock (SCK), it is always
   output direction
2. Use another GPIO as DATA, dynamic setting it to
   input(read) or output(write) direction

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Taroko Connections
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Start Transmission and Send Command

• How to start
• What are the commands available

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An Example SHT11
Pull-up
Data pin in output direction
Set data pin to input direction, then SHT11
controls the DATA line

• Timing diagram

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Software Implementation
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Software Implementation
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Software Implementation
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Convert to Physical Values

• 12-bit humidity, 14-bit temperature
• Temperature
• Humidity

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Device Driver

• Download here
• http//nslab.ee.ntu.edu.tw/courses/wsn-labs-spring
  -09/labs/sht11Driver.rar
• Important functions in SHT1x_sensirion.c
• void sht1xInit()
• void sht1xReset()
• char sht1xMeasure(unsigned char p_value,
  unsigned char p_checksum, unsigned char mode)
• void sht1xCalculate(float p_humidity ,float
  p_temperature)

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Functions

• char sht1xMeasure(unsigned char p_value,
  unsigned char p_checksum, unsigned char mode)
• mode TEMP, HUMI
• Store measured value to p_value
• Store 8-CRC checksum to p_checksum
• void sht1xCalculate(float p_humidity ,float
  p_temperature)
• Convert measured value to physical value
• Put the measured value in p_humidity,
  p_temperature
• Result will also place in p_humidity,
  p_temperature (overwrite)

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Example
44
Outline

• More peripherals
• Watchdog Timer
• Supply Voltage Supervisor (SVS)
• Direct Memory Access (DMA)
• Flash Memory Controller
• External 8Mbit Flash Memory M25P80
• Temperature/humidity sensor SHT11
• Low Power Modes
• MSP430 Software Coding Techniques

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MSP430 Clock System
high-frequency oscillator (optional)
MSP430
digitally controlled oscillator
Clock Signals
Clock Modules
CPU
DCOCLK
MCLK Master Clock
XT2CLK
SMCLK Sub-main clock
Peripherals Timer, UART,
LFXT1CLK
ACLK Auxiliary clock
32.768KHz fixed rate
Low-frequency/high-frequency oscillator
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MSP430 Power Consumption Characteristics

• Current increase with clock frequency
• Current increase with supply voltage
• Supply voltage vs frequency
• More active peripherals means more current
  consumption

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Operating Modes

• MSP430 has six operating modes
• The operating modes take into account three
  different needs
• Ultralow-power
• Speed and data throughput
• Minimization of individual peripheral current
  consumption
• Turn off different clocks in different operating
  mode

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Operating Modes
49
Typical Current Consumption
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Low Power Modes

• Different low power mode disable different clocks
• Peripherals operating with any disabled clock are
  disabled until the clock becomes active
• Wake up is possible through all enabled
  interrupts
• Returns to the previous operating mode if the
  status register value is not altered during the
  ISR

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Code Flow
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Enter/Leave LPM
Intrinsic function
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Which LPM To Enter?

• Depends on your configuration
• MSP430 has a flexible clock system
• Clock signal can select different clock source
• Peripheral can be configure to use different
  clock signal
• Which clock signal still require when system goes
  to sleep
• Remember the peripherals that use the clock
  signal will also be disabled

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Cautions

• Wakeup latency
• Clock module require some time to get stable
• DCO less than 6 µS
• Low frequency oscillator (32.768KHz) hundreds of
  milliseconds
• Temperature drift
• DCO change with temperature
• If temperature is possible to changes
  significantly, re-calibrate DCO when leaving low
  power mode
• If DCO varying too large, some peripherals might
  not function correctly, ex. UART

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Typical Configuration
MSP430
digitally controlled oscillator
Clock Signals
Clock Modules
CPU
DCOCLK
MCLK Master Clock
XT2CLK
SMCLK Sub-main clock
Peripherals Timer, UART,
LFXT1CLK
ACLK Auxiliary clock
32.768KHz fixed rate
56
Useful Mode

• LPM0
• CPU, MCLK off
• DCO, SMCLK, ACLK on
• Power consumption 60 µA (Taroko)
• SMCLK still required
• Ex. UART use SMCLK
• LPM3
• CPU, MCLK, DCO, SMCLK off
• ACLK on
• Power consumption 7 µA (Taroko)
• Only ACLK required
• Timer use ACLK (time keeping)

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Principles for Low-Power Applications

• Maximize the time in LPM3
• Use interrupts to wake the processor and control
  program flow
• Peripherals should be switched on only when
  needed
• Use low-power integrated peripheral modules in
  place of software driven functions
• For example Timer PWM, DMA

58
MSP430 Software Coding Techniques

• Using these methods can greatly reduce debug time
  and/or provide additional robustness in the field
• Some should be used in every program, while some
  are situation dependent

59
Techniques

• First Things First Configure the Watchdog and
  Oscillator
• Configuring the watchdog should be among the
  first actions taken by any MSP430 program
• Using a low-frequency crystal on LFXT1 with a
  device from the 4xx or 2xx families, the code
  should configure the internal load capacitance
  (not for MSP430F1611)

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Techniques

• Always Use Standard Definitions From TI Header
  Files
• This is what we do
• Using Intrinsic Functions to Handle Low Power
  Modes and Other Functions

Intrinsic function
61
Techniques

• Write Handlers for Oscillator Faults
• In MSP430F1611, you can only delay for some time
  to ensure the low frequency oscillator to stable
• The other MSP430 family has specific circuit to
  detect
• Increasing the MCLK Frequency
• Make sure you have enough voltage level to
  operate at the frequency you set
• Or unpredictable behavior
  can occur

62
Techniques

• Using a low-level initialization function
• Problem
• By default, when a C compiler generates assembly
  code, it creates code that initializes all
  declared memory and inserts it before the first
  instruction of the main() function
• In the event that the amount of declared memory
  is large
• The time required to initialize the long list of
  variables may be so long that the watchdog
  expires before the first line of main() can be
  executed
• Solution
• Disables the initialization of memory elements
  that don't need pre-initialization
• __no_init int x_array2500
• Use a compiler-defined low-level initialization
  function

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Techniques

• In-System Programming (ISP)
• If using the MSP430 ISP functionality to write to
  flash memory
• Set the correct timing value (257 kHz to 476
  kHz)
• Set the flash lock bit after the ISP operation is
  complete
• Take care that the cumulative programming time
• Provide sufficient VCC
• Using Checksums to Verify Flash Integrity
• Flash memory data may corrupt, use checksum to
  verify flash integrity periodically