SAM4S Xplained

This README discusses issues unique to NuttX configurations for the Atmel SAM4S Xplained development board. This board features the ATSAM4S16C MCU with 1MB FLASH and 128KB.

The SAM4S Xplained features:

  • 120 MHz Cortex-M4 with MPU

  • 12MHz crystal (no 32.768KHz crystal)

  • Segger J-Link JTAG emulator on-board for program and debug

  • MICRO USB A/B connector for USB connectivity

  • IS66WV51216DBLL ISSI SRAM 8Mb 512K x 16 55ns PSRAM 2.5v-3.6v

  • Four Atmel QTouch buttons

  • External voltage input

  • Four LEDs, two controllable from software

  • Xplained expansion headers

  • Footprint for external serial Flash (not fitted)

PIO Muliplexing

PIN

FUNCTION

PA0

SMC_A17

PA1

SMC_A18

PA2

J3.7 default

PA3

J1.1 & J4.1

PA4

J1.2 & J4.2

PA5

User_button BP2

PA6

J3.7 optional

PA7

CLK_32K

PA8

CLK_32K

PA9

RX_UART0

PA10

TX_UART0

PA11

J3.2 default

PA12

MISO

PA13

MOSI

PA14

SPCK

PA15

J3.5

PA16

J3.6

PA17

J2.5

PA18

J3.4 & SMC_A14

PA19

J3.4 optional & SMC_A15

PA20

J3.1 & SMC_A16

PA21

J2.6

PA22

J2.1

PA23

J3.3

PA24

TSLIDR_SL_SN

PA25

TSLIDR_SL_SNSK

PA26

TSLIDR_SM_SNS

PA27

TSLIDR_SM_SNSK

PA28

TSLIDR_SR_SNS

PA29

TSLIDR_SR_SNSK

PA30

J4.5

PA31

J1.5

PB0

J2.3 default

PB1

J2.4

PB2

J1.3 & J4.3

PB3

J1.4 & J4.4

PB4

JTAG

PB5

JTAG

PB6

JTAG

PB7

JTAG

PB8

CLK_12M

PB9

CLK_12M

PB10

USB_DDM

PB11

USB_DDP

PB12

ERASE

PB13

J2.3 optional

PB14

N/A

PC0

SMC_D0

PC1

SMC_D1

PC2

SMC_D2

PC3

SMC_D3

PC4

SMC_D4

PC5

SMC_D5

PC6

SMC_D6

PC7

SMC_D7

PC8

SMC_NWE

PC9

Power on detect

PC10

User LED D9

PC11

SMC_NRD

PC12

J2.2

PC13

J2.7

PC14

SMC_NCS0

PC15

SMC_NSC1

PC16

N/A

PC17

User LED D10

PC18

SMC_A0

PC19

SMC_A1

PC20

SMC_A2

PC21

SMC_A3

PC22

SMC_A4

PC23

SMC_A5

PC24

SMC_A6

PC25

SMC_A7

PC26

SMC_A8

PC27

SMC_A9

PC28

SMC_A10

PC29

SMC_A11

PC30

SMC_A12

PC31

SMC_A13

Buttons and LEDs

Buttons

The SAM4S Xplained has two mechanical buttons. One button is the RESET button connected to the SAM4S reset line and the other is a generic user configurable button labeled BP2 and connected to GPIO PA5. When a button is pressed it will drive the I/O line to GND.

LEDs

There are four LEDs on board the SAM4X Xplained board, two of these can be controlled by software in the SAM4S:

LED

GPIO

D9 Yellow LED

PC10

D10 Yellow LED

PC17

Both can be illuminated by driving the GPIO output to ground (low).

These LEDs are not used by the board port unless CONFIG_ARCH_LEDS is defined. In that case, the usage by the board port is defined in include/board.h and src/sam_leds.c. The LEDs are used to encode OS-related events as follows:

SYMBOL

Meaning

D9

D10

LED_STARTED

NuttX has been started

OFF

OFF

LED_HEAPALLOCATE

Heap has been allocated

OFF

OFF

LED_IRQSENABLED

Interrupts enabled

OFF

OFF

LED_STACKCREATED

Idle stack created

ON

OFF

LED_INIRQ

In an interrupt

N/C

N/C

LED_SIGNAL

In a signal handler

N/C

N/C

LED_ASSERTION

An assertion failed

N/C

N/C

LED_PANIC

The system has crashed

OFF

Blinking

LED_IDLE

MCU is is sleep mode

N/A

N/A

Thus if D9 is statically on, NuttX has successfully booted and is, apparently, running normmally. If D10 is flashing at approximately 2Hz, then a fatal error has been detected and the system has halted.

Serial Consoles

UART1

If you have a TTL to RS-232 converter then this is the most convenient serial console to use. UART1 is the default in all of these configurations.

SIGNAL

CONNECTOR

CONNECTOR

UART1 RXD PB2

J1 pin 3

J4 pin 3

UART1 TXD PB3

J1 pin 4

J4 pin 4

GND

J1 pin 9

J4 pin 9

Vdd

J1 pin 10

J4 pin 10

USART1

USART1 is another option:

SIGNAL

CONNECTOR

USART1 RXD PA21

J2 pin 6

USART1 TXD PA22

J2 pin 1

GND

J2 pin 9

Vdd

J2 pin 10

Virtual COM Port

Yet another option is to use UART0 and the virtual COM port. This option may be more convenient for long term development, but was painful to use during board bring-up.

The SAM4S Xplained contains an Embedded Debugger (EDBG) that can be used to program and debug the ATSAM4S16C using Serial Wire Debug (SWD). The Embedded debugger also include a Virtual Com port interface over USART1. Virtual COM port connections:

AT91SAM4S16

ATSAM3U4CAU

PA9 RX_UART0

PA9_4S PA12

PA10 TX_UART0

RX_3U PA11

SAM4S Xplained-specific Configuration Options

  • CONFIG_ARCH: Identifies the arch/ subdirectory. This should be set to:

    • CONFIG_ARCH=arm

  • CONFIG_ARCH_family: For use in C code:

    • CONFIG_ARCH_ARM=y

  • CONFIG_ARCH_architecture: For use in C code:

    • CONFIG_ARCH_CORTEXM4=y

  • CONFIG_ARCH_CHIP: Identifies the arch/*/chip subdirectory

    • CONFIG_ARCH_CHIP="sam34"

  • CONFIG_ARCH_CHIP_name: For use in C code to identify the exact chip:

    CONFIG_ARCH_CHIP_SAM34 CONFIG_ARCH_CHIP_SAM4S CONFIG_ARCH_CHIP_ATSAM4S16C

  • CONFIG_ARCH_BOARD: Identifies the boards/ subdirectory and hence, the board that supports the particular chip or SoC.

    • CONFIG_ARCH_BOARD=sam4s:xplained (for the SAM4S Xplained development board)

  • CONFIG_ARCH_BOARD_name: For use in C code

    • CONFIG_ARCH_BOARD_SAM4S_XPLAINED=y

  • CONFIG_ARCH_LOOPSPERMSEC: Must be calibrated for correct operation of delay loops

  • CONFIG_ENDIAN_BIG: define if big endian (default is little endian)

  • CONFIG_RAM_SIZE: Describes the installed DRAM (SRAM in this case):

    • CONFIG_RAM_SIZE=0x00008000 (32Kb)

  • CONFIG_RAM_START: The start address of installed DRAM

    • CONFIG_RAM_START=0x20000000

  • CONFIG_ARCH_LEDS: Use LEDs to show state. Unique to boards that have LEDs

  • CONFIG_ARCH_INTERRUPTSTACK: This architecture supports an interrupt stack. If defined, this symbol is the size of the interrupt stack in bytes. If not defined, the user task stacks will be used during interrupt handling.

  • CONFIG_ARCH_STACKDUMP: Do stack dumps after assertions

  • CONFIG_ARCH_LEDS: Use LEDs to show state. Unique to board architecture.

Individual subsystems can be enabled:

  • CONFIG_SAM34_RTC: Real Time Clock

  • CONFIG_SAM34_RTT: Real Time Timer

  • CONFIG_SAM34_WDT: Watchdog Timer

  • CONFIG_SAM34_UART0: UART 0

  • CONFIG_SAM34_UART1: UART 1

  • CONFIG_SAM34_SMC: Static Memory Controller

  • CONFIG_SAM34_USART0: USART 0

  • CONFIG_SAM34_USART1: USART 1

  • CONFIG_SAM34_HSMCI: High Speed Multimedia Card Interface

  • CONFIG_SAM34_TWI0: Two-Wire Interface 0

  • CONFIG_SAM34_TWI1: Two-Wire Interface 1

  • CONFIG_SAM34_SPI0: Serial Peripheral Interface

  • CONFIG_SAM34_SSC: Synchronous Serial Controller

  • CONFIG_SAM34_TC0: Timer Counter 0

  • CONFIG_SAM34_TC1: Timer Counter 1

  • CONFIG_SAM34_TC2: Timer Counter 2

  • CONFIG_SAM34_TC3: Timer Counter 3

  • CONFIG_SAM34_TC4: Timer Counter 4

  • CONFIG_SAM34_TC5: Timer Counter 5

  • CONFIG_SAM34_ADC12B: 12-bit Analog To Digital Converter

  • CONFIG_SAM34_DACC: Digital To Analog Converter

  • CONFIG_SAM34_PWM: Pulse Width Modulation

  • CONFIG_SAM34_CRCCU: CRC Calculation Unit

  • CONFIG_SAM34_ACC: Analog Comparator

  • CONFIG_SAM34_UDP: USB Device Port

Some subsystems can be configured to operate in different ways. The drivers need to know how to configure the subsystem.

  • CONFIG_SAM34_GPIOA_IRQ

  • CONFIG_SAM34_GPIOB_IRQ

  • CONFIG_SAM34_GPIOC_IRQ

  • CONFIG_USART0_SERIALDRIVER

  • CONFIG_USART1_SERIALDRIVER

  • CONFIG_USART2_SERIALDRIVER

  • CONFIG_USART3_SERIALDRIVER

ST91SAM4S specific device driver settings

  • CONFIG_U[S]ARTn_SERIAL_CONSOLE - selects the USARTn (n=0,1,2,3) or UART m (m=4,5) for the console and ttys0 (default is the USART1).

  • CONFIG_U[S]ARTn_RXBUFSIZE - Characters are buffered as received. This specific the size of the receive buffer

  • CONFIG_U[S]ARTn_TXBUFSIZE - Characters are buffered before being sent. This specific the size of the transmit buffer

  • CONFIG_U[S]ARTn_BAUD - The configure BAUD of the UART. Must be

  • CONFIG_U[S]ARTn_BITS - The number of bits. Must be either 7 or 8.

  • CONFIG_U[S]ARTn_PARTIY - 0=no parity, 1=odd parity, 2=even parity

  • CONFIG_U[S]ARTn_2STOP - Two stop bits

Configurations

Each SAM4S Xplained configuration is maintained in a sub-directory and can be selected as follow:

$ tools/configure.shsam4s-xplained:<subdir>

Before building, make sure the PATH environment variable includes the correct path to the directory than holds your toolchain binaries.

And then build NuttX by simply typing the following. At the conclusion of the make, the nuttx binary will reside in an ELF file called, simply, nuttx.

$ make

The <subdir> that is provided above as an argument to the tools/configure.sh must be is one of the following.

  1. These configurations use the mconf-based configuration tool. To change any of these configurations using that tool, you should:

    1. Build and install the kconfig-mconf tool. See nuttx/README.txt see additional README.txt files in the NuttX tools repository.

    2. Execute ‘make menuconfig’ in nuttx/ in order to start the reconfiguration process.

  2. Unless stated otherwise, all configurations generate console output on UART1 which is available on J1 or J4 (see the section “Serial Consoles” above). USART1 or the virtual COM port on UART0 are options. The virtual COM port could be used, for example, by reconfiguring to use UART0 like:

    System Type -> AT91SAM3/4 Peripheral Support

    • CONFIG_SAM_UART0=y

    • CONFIG_SAM_UART1=n

    Device Drivers -> Serial Driver Support -> Serial Console

    • CONFIG_UART0_SERIAL_CONSOLE=y

    Device Drivers -> Serial Driver Support -> UART0 Configuration

    • CONFIG_UART0_2STOP=0

    • CONFIG_UART0_BAUD=115200

    • CONFIG_UART0_BITS=8

    • CONFIG_UART0_PARITY=0

    • CONFIG_UART0_RXBUFSIZE=256

    • CONFIG_UART0_TXBUFSIZE=256

  3. Unless otherwise stated, the configurations are setup for Linux (or any other POSIX environment like Cygwin under Windows):

Build Setup:

  • CONFIG_HOST_LINUX=y: Linux or other POSIX environment

  1. These configurations use the older, OABI, buildroot toolchain. But that is easily reconfigured:

    System Type -> Toolchain:

    • CONFIG_ARM_TOOLCHAIN_BUILDROOT=y: Buildroot toolchain

    • CONFIG_ARM_TOOLCHAIN_BUILDROOT_OABI=y: Older, OABI toolchain

    If you want to use the Atmel GCC toolchain, here are the steps to do so:

    Build Setup:

    • CONFIG_HOST_WINDOWS=y: Windows

    • CONFIG_HOST_CYGWIN=y: Using Cygwin or other POSIX environment

    System Type -> Toolchain:

    • CONFIG_ARM_TOOLCHAIN_GNU_EABI=y: General GCC EABI toolchain under windows

    This re-configuration should be done before making NuttX or else the subsequent ‘make’ will fail. If you have already attempted building NuttX then you will have to:

    1. make distclean to remove the old configuration

    2. tools/configure.sh sam3u-ek/ksnh to start with a fresh configuration, and

    3. Perform the configuration changes above.

    Also, make sure that your PATH variable has the new path to your Atmel tools. Try which arm-none-eabi-gcc to make sure that you are selecting the right tool.

    See also the “NOTE about Windows native toolchains” in the section call “GNU Toolchain Options” above.

nsh

This configuration directory will built the NuttShell.

The configuration configuration can be modified to include support for the on-board SRAM (1MB).

System Type -> External Memory Configuration

  • CONFIG_SAM34_EXTSRAM0=y: Select SRAM on CS0

  • CONFIG_SAM34_EXTSRAM0SIZE=1048576: Size=1MB

Now what are you going to do with the SRAM. There are two choices:

  1. To enable the NuttX RAM test that may be used to verify the external SRAM:

    System Type -> External Memory Configuration

    • CONFIG_SAM34_EXTSRAM0HEAP=n: Don’t add to heap

    Application Configuration -> System NSH Add-Ons

    • CONFIG_TESTING_RAMTEST=y: Enable the RAM test built-in

    In this configuration, the SDRAM is not added to heap and so is not excessible to the applications. So the RAM test can be freely executed against the SRAM memory beginning at address 0x6000:0000 (CS0).

    nsh> ramtest -h
Usage: <noname> [-w|h|b] <hex-address> <decimal-size>

Where:
  <hex-address> starting address of the test.
  <decimal-size> number of memory locations (in bytes).
  -w Sets the width of a memory location to 32-bits.
  -h Sets the width of a memory location to 16-bits (default).
  -b Sets the width of a memory location to 8-bits.

    To test the entire external SRAM:

nsh> ramtest 60000000 1048576
RAMTest: Marching ones: 60000000 1048576
RAMTest: Marching zeroes: 60000000 1048576
RAMTest: Pattern test: 60000000 1048576 55555555 aaaaaaaa
RAMTest: Pattern test: 60000000 1048576 66666666 99999999
RAMTest: Pattern test: 60000000 1048576 33333333 cccccccc
RAMTest: Address-in-address test: 60000000 1048576

  1. To add this RAM to the NuttX heap, you would need to change the configuration as follows:

    System Type -> External Memory Configuration

    • CONFIG_SAM34_EXTSRAM0HEAP=y: Add external RAM to heap

    Memory Management

    • -CONFIG_MM_REGIONS=1: Only the internal SRAM

    • +CONFIG_MM_REGIONS=2: Also include external SRAM