README
======
This README discusses issues unique to NuttX configurations for the
OPEN ISA RV32M1-VEGA development board featuring the RV32M1 MCU. The
RV32M1 is a heterogeneous soc including an ARM Cortex-M4 CPU, an ARM
Cortex-M0+ CPU, a RISC-V RI5CY CPU, and a RISC-V ZERO_RISCY CPU. the
SOC integrates 1.25 MB flash, 384 KB SRAM, and varieties of peripherals.
The RV32M1-VEGA board features:
- On-board OpenSDA Debug Adapter,
- USB Device Port,
- FXOS8700CQ Digital Combo Sensor: 3D Accelerometer + 3D Magnetometer,
- Wirless Abilities: BLE, Generic FSK, and IEEE Std.802.15.4(Thread),
- ONE user RGB LED,
- Four user push-buttons,
- 4 MB external SPI Flash,
- Micro-SD Card Slot on the backside,
- Arduino R3 Compatible IO Header.
Refer to https://open-isa.org for further information about this board.
Currently NuttX is ported to RV32M1 RI5CY only. RI5CY is RV32IMC RISC-V CPU
with PULP extensions features:
- Post-Incrementing load and stores,
- Multiply-Accumulate extensions,
- ALU extensions,
- Hardware Loops.
Contents
========
- LEDs
- UARTs
- Buttons
- ITCM
- TSTMR
LEDs
====
The RV32M1-VEGA board has ONE user RGB LED; Only the red part led is used to
indicate an interrupt request is being serviced.
SYMBOL Meaning RED* GREEN BLUE
------------------- ----------------------- ------- ------- -----
LED_STARTED NuttX has been started OFF OFF OFF
LED_HEAPALLOCATE Heap has been allocated OFF OFF OFF
LED_IRQSENABLED Interrupts enabled OFF OFF OFF
LED_STACKCREATED Idle stack created OFF OFF OFF
LED_INIRQ In an interrupt** OFF OFF OFF
LED_SIGNAL In a signal handler*** OFF OFF OFF
LED_ASSERTION An assertion failed OFF OFF OFF
LED_PANIC The system has crashed OFF OFF OFF
LED_CPU Interrupt service ON OFF OFF
UARTs
====
LPUART PINS
---------------
LPUART0
RX PC7, PB25, PA2
TX PC8, PB26, PA3
LPUART1
RX PB2, PC29, PA2, PA25
TX PB3, PC30, PA3, PA26
LPUART2
RX PB11, PB18, PB1
TX PB12, PB19, PB0
LPUART3
RX PB28, PE8, PE29
TX PB29, PE9, PE30
Default LPUART Configuration
--------------------------------
LPUART0 is enabled in most configurations (see */defconfig). RX and TX are
configured on pins PC7 and PC8, respectively (see include/board.h). These
two above pins are connected to onboard Debug Adapter which provides a USB-
TTL serial channel.
Buttons
====
Four tactile buttons are populated on RV32M1-VEGA Board.
Buttons PINS Assignment
---------------
NAME PIN EXTERNAL-PULLUP
SW2 PA0 YES
SW3 PE8 NO
SW4 PE9 NO
SW5 PE12 NO
All these buttons can be used as interrupt and wake up sources while SW2 can
be an alternative NMI Source.
ITCM
====
A 64KB ITCM is coupled with M4 Cores, RI5CY CPU or ARM Cortex-M4 CPU. If the
ITCM is selected, Critical Codes including but not limited to Exception Vectors,
Interrupt Service Routines will be placed in ITCM.
TSTMR
====
TSTMR Module is embedded in RV32M1 to provide system time stamp. It runs off 1MHz
with a 56-bit counter, and can be adopted to get more accurate delay counting. If
the Module is selected, a hardware delay method will replace mdealy and udelay,
the built-in software delay methods.
TOOLCHAIN
========
It is preferable to use OPEN ISA gcc Toolchain to exploit RV32M1 RI5CY capabi-
lities, though the generic GNU RVG Toolchain can generate binary codes running
on RV32M1 RI5CY without any problems. To switch generic GNU RVG Toolchain to
OPEN ISA Toolchain, the following option must be selected:
Board Selection --->
[*] Utilize OPEN ISA Toolchain
Make sure OPEN ISA Toolchain have been installed and be found in PATH.
ARCHCPUFLAGS
====
RI5CY Core supports hardware loop with 6 hardware loop registers assistance,
these registers could be overwritten when contexts switch. If codes are generated
by OPEN ISA Toolchain and CONFIG_ARCH_RISCV_INTXCPT_EXTREGS is not less than 6,
the RI5CY specific architecture flag will be passed to gcc compiler. In that case,
the 6 hardware loop registers must be saved and restored in interrupt routines with
the general purpose registers.
You will see the following lines in Make.defs file:
ARCHCPURV32IM = -march=rv32imc -mabi=ilp32
ifeq ($(CONFIG_RV32M1_OPENISA_TOOLCHAIN),y)
ifdef CONFIG_ARCH_RISCV_INTXCPT_EXTREGS
ifeq ($(filter 0 1 2 3 4 5 , $(CONFIG_ARCH_RISCV_INTXCPT_EXTREGS)),)
ARCHCPURV32IM = -march=rv32imcxpulpv2
endif
endif
endif
ARCHCPUFLAGS = $(ARCHCPURV32IM)
CONFIG_ARCH_RISV_INTXCPT_EXTREGS could be configured in the following menu:
System Type --->
[*] RISC-V Integer Context Extensions
(6) Number of Extral RISC-V Integer Context Registers
Program & Debug
========
Program
====
To program RV32M1, openocd from OPEN ISA and an external jtag adapter are pre-
requisite. There are 2 tested jtag adapters: Segger Jlink EDU mini and SiPEED
USB Jtag Adapter. The Segger Jlink EDU mini can connect J55 header on RV32M1-VEGA
board directly while SiPEED USB Jtag Adapter has to co-operate with an Adapter
board to setup wires connection.
Compared to Segger Jlink EDU Mini Adapter, SiPEED USB Jtag Adapter is cheaper but
not inferior.
With SiPEED USB Jtag Adapter, some patches must be applied to rv32m1_ri5cy.cfg:
--- a/rv32m1_ri5cy.cfg
+++ b/rv32m1_ri5cy.cfg
@@ -2,7 +2,11 @@ set _WORKAREASIZE 0x2000
adapter_khz 1000
-interface jlink
+interface ftdi
+ftdi_vid_pid 0x0403 0x6010
+ftdi_layout_init 0x0508 0x0f1b
+ftdi_layout_signal nTRST -data 0x0200 -noe 0x0100
+ftdi_layout_signal nSRST -data 0x0800 -noe 0x0400
transport select jtag
set _WORKAREASIZE 0x1000
------------------------------
Make sure that RV32M1 boots RI5CY, and you do this ONLY ONCE. Refer to RV32M1-VEGA
quick start guide for more details.
Note:
OPEN ISA Toolchain, rv32m1_ri5cy.cfg contained in RV32M1 SDK, and RV32M1-VEGA
quick start guide could be found in the following link:
https://open-isa.org/downloads/
Debug
====
riscv64-unknonw-elf-gdb can not debug RV32M1 RISC-V Cores currently. GDB from
OPEN ISA Toolchain seems the only option and even can debug elf files generated
by risc64-unknown-elf-* tools.
Configuration Sub-directories
========
NuttX of all configurations in rv32m1-vega/configs can be compiled by
the generic GNU RVG Toolchain and OPEN ISA Toolchain.
buttons
====
This configuration is a variant of the NSH configuration used for
demonstrating the four buttons on RV32M1-VEGA board.
Example usage of buttons:
a. Start the buttons daemon:
nsh> buttons
b. Press and release SW2, SW3, SW4, SW5 freely, the button pressed
and released messages will display correspondingly.
nsh
====
This configuration is basic. getprime is included in this configuration to
determine performance of RV32M1 RI5CY Core.
nsh-itcm
====
This configuration is a variant of the NSH configuration used for
demonstrating ITCM. When ITCM is selected, RI5CY Exception Vectors and
Interrupt Service Routines are placed in ITCM. Performance can be calculated
by getprime, and you might find it deteriorated a little ironically. The drawback
may be caused by long jump frequently between ITCM and flash. Besides, an instr-
uction cache is enabled always after RI5CY resets, and amelioration could not be
achieved with even ITCM enabled.
What if codes fulfill the 64KB ITCM ?