Fernly is a simple operating system designed for use in the reverse engineering of the Fernvale CPU. It will likely be disposed of when the system has been understood well enough to implement a full operating system.

This is a port for the rephone based on a MT2502A

http://www.seeed.cc/rephone/

Download the arm gcc compiler from

https://launchpad.net/gcc-arm-embedded/+milestone/4.9-2014-q4-major

To compile, simply run "make". If you're cross-compiling, set CROSS_COMPILE to the prefix of your cross compiler. This is very similar to how to compile for Linux.

For example:

 make CROSS_COMPILE= <path>/gcc-arm-none-eabi-4_9-2014q4/bin/arm-none-eabi-

Run the following command and connect the target device

./firmwareUploader.py --firmPath ./build/mt2502a.bin  --nobat --native

Connect the port /dev/ttyUSB0

fenly>help
Fernly shell help.  Available commands:                                         
    help    Print help about available commands                             
    hex     Print area of memory as hex                                     
    peek    Look at one area of memory                                      
    poke    Write a value to an area of memory                              
    spi     Manipulate on-board SPI                                         
    spi_raw Manipulate on-board SPI (raw interface)                         
    led     Turn the on-board LED on or off                                 
    load    Load data to a specific area in memory                          
    loadjmp Load data to a specific area in memory, then jump to it         
fernly> 

Help

fernly> led                                                                     
Usage: led  [0 = green 1 = red 2 = blue] [1 = on, 0 = off]                      
fernly> 

Switch Led on

fernly> led 1 1                                                                 
fernly> 	

Since Fernvale is based on a Mediatek chip, ModemManager will, by default, try to treat it as a modem and make it available for network connections. This is undesirable.

To work around this problem, create a udev rule under /etc/udev/rules.d/ called 98-fernvale.rules with the following contents:

SUBSYSTEM=="tty", ATTRS{idVendor}=="0e8d",\
    ATTRS{idProduct}=="0003",\
    MODE="0660", SYMLINK+="fernvale"

ACTION=="add|change", SUBSYSTEM=="usb",\
    ENV{DEVTYPE}=="usb_device", ATTRS{idVendor}=="0e8d",\
    ATTRS{idProduct}=="0003",\
    ENV{ID_MM_DEVICE_IGNORE}="1"

The default OSX CDC matches as /dev/cu.usbmodem1410 or /dev/cu.usbmodem1420

Fernly includes a special 'flashrom' mode that allows for direct communication with the flashrom program to manipulate the onboard SPI. The protocol is binary, and can be entered by issuing the following command:

spi flashrom

Fernly will respond with a binary 0x05, indicating it is ready.

The format of the protocol is very simple. The host writes the number of bytes to write, then the number of bytes to read, and then writes the data to send to the flash chip. It then reads the requested number of bytes. For example, to send a 2-byte command '0xfe 0xfa' followed by a 3-byte response, write the following data to the serial port:

| 02 03 fe fa |

Then read three bytes of data from the serial port.

A maximum of 255 bytes may be transmitted and received at one time, though in practice these numbers may be smaller.

To exit 'spi flashrom' mode and return to fernly, read/write zero bytes. That is, send the following packet:

| 00 00 |

See read_flash for user-level instructions how to backup/restore FlashROM of your device.

Fernly is licensed under the BSD 2-clause license (see LICENSE).

Previous versions of fernly linked against division libraries taken from U-Boot, which were licensed under GPL-2. These files have been removed.

Instead, we supply a version of libgcc.a. This file was extracted from a standard gcc toolchain, specifically:

https://code.google.com/p/yus-repo/downloads/detail?name=arm-none-eabi-4.6-armv5.tar.gz

It has not been modified, and its distribution here should be covered under the "runtime exception".