VME-SAM3X firmware

Tools required for building on Ubuntu 24.04 LTS:

• gcc-arm-none-eabi
• libnewlib-arm-none-eabi
• make

When installing the tools needed for building, you might want to specify --no-install-recommends in order to avoid also installing the C++ standard library for ARM, which is very large and not needed by this project. For example:

apt-get install --no-install-recommends \
  gcc-arm-none-eabi libnewlib-arm-none-eabi make

Tools required for installing the firmware image:

• bossa

Building

make clean; make all

Installation

• Power up VME-EVM-300 or VME-EVR-300 with jumper installed in SAM Erase header.
• Remove jumper and power cycle.
• Connect USB cable to USB port in front panel.
• Run bossac -e -w -v -b -p /dev/ttyUSB1 build/EVM_300_UDP.bin
• Power cycle.

There is an alternative method for installing the firmware image, but it is only easier when one has already setup debugging (OpenOCD must be running and connected to the target device):

make install

Debugging

GDB and OpenOCD can be used in order to debug (and install) the firmware. For this, you have to install two additional packages:

• gdb-arm-none-eabi
• openocd

Connect a USB cable to the USB port in the front panel and then run:

openocd -f OpenOCD/mrf-vme-usb.cfg -f OpenOCD/vme-evm-300.cfg

(for the VME-EVM-300) or

openocd -f OpenOCD/mrf-vme-usb.cfg -f OpenOCD/vme-evr-300.cfg

(for the VME-EVR-300).

Open a separate terminal and ensure that the correct firmware image is loaded (GDB cannot work correctly if the running image and the image used by GDB differ). In case of doubt, run make install to install the built image. Subsequently, run the following command to launch GDB and connect it to the device.

make debug

This assumes that OpenOCD is running on the same host as GDB and listening for a connection from GDB on port 3333. If this does not apply, you have to modify .gdbinit.

Network Protocol

The firmware for the SAM3X implements a UDP/IP server that listens on UDP port 2000. There are two versions of the protocol: The older version (version 1) is identical to the one that is supported by older devices from the VME-EVG-230 and VME-EVR-230 series that use an IP2022 instead of a SAM3X. The newer version (version 2) is exclusively supported by recent versions of the firmware for the SAM3X and adds support for accessing 32-bit registers in a single round-trip.

Packets for protocol version 1 have the following structure:

Field type	Field length (in bytes)	Description
uint8	1	access type
int8	1	status
uint16	2	data
uint32	4	address
uint32	4	reference

Packets for protocol version 2 have the following structure:

Field type	Field length (in bytes)	Description
uint8	1	access type
int8	1	status
uint16	2	reserved
uint32	4	address
uint32	4	reference
uint32	4	data

All fields use network byte-order (big endian).

The access type field specifies the action that is taken. Protocol version 1 supports two access types:

• 1: read from 16-bit register
• 2: write to 16-bit register

Protocol version 2 supports two additional access types:

• 3: write to 16-bit register and do not read back
• 4: read from 32-bit register
• 5: write to 32-bit register
• 6: write to 32-bit register and do not read back

It is still possible to read from and write to 32-bit registers using version 1 of the protocol, but this requires two round-trips: For read operations, the low word (starting at the register address plus two bytes) should be read first, and the high word (the two bytes starting at the register address) should be read second. For write operations, the high word should be written first, and the low word should be written second (after the first write operation has succeeded).

The status field is only used in replies to requests and should be set to zero in requests. It can have the following values:

• 0: Operation succeeded.
• -1 (0xFF): Invalid address specified (this is never returned by the current version of the firmware).
• -2 (0xFE): FPGA did not respond in time (timeout).
• -3 (0xFD): Invalid command (the access type field contains a value that is not supported for the respective version of the protocol).

The reserved field in version 2 of the protocol is not used at the moment and should be set to zero in requests.

The address field specifies the address of the requested register inside the FPGA. Depending on the address space that shall be accessed the following offsets need to be applied (please note that these values are only valid for the VME-EVM-300 and VME-EVR-300, other devices may use different offsets):

Offset	Address space
0x00000000	VME CR/CSR address space
0x80000000	EVM or EVR address space

The reference field in a request can contain an arbitrary number chosen by the client. Each response contains the reference value from the respective request, so clients can use this field to associate responses with requests.

The data field contains the value that is supposed to be written (for write requests) or the value that has been read (for responses). For read requests, the value in this field is ignored. For responses to write requests, this is not the value that has been written but rather the value that was read back from the register after a successful write operation, unless the “no readback” variant of the write operation was used. If the status field of a response is non-zero, the value in the data field is invalid and should not be used.