SanDisk Sansa Connect

History/Background

The Sansa Connect is designed by Zing System Inc. (part of Dell), who showed off a WIFI device for listening to streaming radio stations, without any onboard storage. A prototype device was announced, but never put into production. Screenshots of the time show a similar UI design to the current Sansa Connect.

The Sansa Connect has 4Gb of onboard flash storage, as well as a Micro-SD slot, capable of using SDHC cards in the newer firmware versions.

Rockbox Status

There is a Sansa Connect Rockbox port in progress. Bootloader can boot both OF (by holding PREV button) and Rockbox. There is no software-only installation method available. To get unsigned code loading it is required to do hardware modification.

Current Rockbox bootloader is supposed to work as replacement for vmlinux. After building bootloader, prepend resulting bootloader.bin file with .srr header

AA BB FF EE 00 00 00 01 10 00 12 00 FI LE SI ZE

where FILESIZE is bootloader.bin file size + 2048 (signature) coded in LE. Then from OF shell overwrite /dev/mtd2 with created file (don't use Recovery Mode as we don't have method yet to remove recoverzap bootloader variable which would result in recovery screen again on next boot).

Booting is quite slow due to bootloader checking signatures (the hardware modification only makes the file to be always accepted, the SHA-1 sum is still computed).

There is possibility to overwrite OF bootloader - if you are risky enough, edit firmware/target/arm/tms320dm320/boot.lds and change FLASH_OFFSET to 0, rebuild bootloader and then using hardware modification method flash the new bootloader (don't append srr header). WARNING: this has not been tested by anyone, we may still be missing some critical initialization (which would mean hard to recover brick).

Device	Status	Comments
LCD driver	90%	Could make better use of OSD/Video windows
Backlight	100%
Storage (SD) driver	90%	Not tested for internal storage (OF uses ext2)
Button driver	90%
USB handler	1%	Clock handling is implemented. Linux sourcecode released by ZING seems to contain driver for TNETV105
RTC driver	0%	RTC doesn't seem to be accessible by I2C. HID_MONOTIME reads difference time, the base time retrieval is unknown (base+difference = Unix time)
Power handling	10%	Battery meter uses fake linear scale (1 mV = 1%). Charging doesn't seem to work properly.
Audio DAC driver	80%
WiFi driver	0%
(Software) I2C driver	90%

Additional work to be done:

• SD driver can use interrupts
• WiFi driver needs to be written (network subsystem needs to be added to Rockbox)
• Battery handling has to be added
• Use internal speaker

Hardware

AnythingButiPod performed a basic disassembly.

Further to this: the EMI shield is a frame and clip-on top shield - only the frame is soldered to the main PCB. The frame visually obscures some of the chips.

• DSP/CPU: TexasInstrumentsTMS320. This is a multicore device consisting of a ARM926EJ-S CPU core and TMS320vc5409 DSP.
• Secondary CPU: ATMEL MEGA165PV. The Atmel AVR line has great support of open source developement tools (GCC et all). It's referred internally as "HID", and it's used as an interface to external devices - handles display sleep & wakeup, for example. Interfaced via SPI.
• Power Management: TI TPS 65021. Interfaced via I2C.
• LCD: 2.2 inch - CT022TND4 V.6 M1-B
• SDRAM: Samsung K4M51323LC-DN75
• USB 2.0: TNETV105. Not to be confused with TI's TNETV105 (DSP/CPU bundle), this handles USB for the device. The TMS320 has an internal USB controller but it is disabled on boot. Interfaced via VLYNQ.
• Codec: Ti AC3106I. DAC and stereo power amplifier, with programmable filters. Most likely interfaced via I2C.
• EEPROM: Atmel AT88SC - 64kbit fused, cryptographically secure. Holds individual device information such as USB deviceid, MAC address and device certificate. Interfaced via I2C.
• Flash: Sandisk SDINB1-4096. 4GB iNAND flash module. Holds filesystem.

Visually obscured chips:

• Flash: Samsung K8D3216UBC (located just under DSP/CPU) - NOR Flash 32MBIT. Holds bootloader, linux kernel, persistent variables, platform.
• WIFI: Murata (chip has the MAC address engraved on it - vendor digits are 00:13:E0) - possible model numbers start KK6T6... or LBWA-.... Interfaced via SPI. Actually, after desoldering the chip, it turned out to be tiny PCB - the chipset is labelled MARVELL W8686B12 717AEUP: http://www.arm9board.net/download/FL6410/datasheet/mavell_88w8686.pdf
• RTC: ST M41T62 - interfacing method unknown
• TPS61042 Led driver (package marking BHS)

Clock speeds

These are obtained from the initialization code on the linux kernel patch for the Connect:

• TMS320 ARM core: 120 MHz
• SDRAM: 72 MHz
• TMS320 DSP core: 72 MHz
• DMA coprocessor: 144 MHz

TMS320 general purpose I/O pins mapping

This is the detail for the known GPIO pins in the Connect:

Pin	Device	Name	Comments	Direction
GIO0	TMS320	STANDBY	Buttons state changed IRQ	In
GIO2	Headphones	PRESENT	Headphones inserted	In
GIO5	iNAND	SELECT	Selects iNAND when low	Out
GIO6	SD Card	SELECT	Selects SD slot when low	Out
GIO7	USB	RESET	TNETV105PAP reset (active low)	Out
GIO8	I2C	INTR	Data available on dock I2C to UART connector (rising edge)	In
GIO9	USB	DETECT	low when USB cable connected	In
GIO11	I2C	DTCT	Available at dock connector, low if I2C to UART is not connected	In
GIO12	I2C	SCL	Available at dock connector (pin 22)	In/Out
GIO13	I2C	SDA	Available at dock connector (pin 21)	In/Out
GIO14	SD Card	CARD_DETECT	Low when card inserted	In
GIO16	AIC3X	MCLK	Audio interface master clock	Out
GIO29	SIF1	ENABLE	AVR's SS (active low)	Out
GIO30	SIF1	Clock		Out
GIO31	SIF1	Data In		In
GIO32	SIF1	Data Out		Out
GIO33	USB	CLK	USB clock (source from M48XI)	Out
GIO34	Backlight	PWM	Backlight PWM (active high)	Out
GIO35	I2C	SDA	I2C data line	In/Out
GIO36	I2C	SCL	I2C clock	In/Out
GIO37	SD Card	CARD_POWER	Powers SD slot when low	Out
GIO38	iNAND	iNAND_POWER	Powers iNAND when low	Out
GIO39	LCD	VENC	FIELD_VENC	Out

Contents of the /proc/gio:

GIO#	User ID	Function	Dir	Invert	Level	IRQ	IRQ Edge	Debounce
0		GIO	in	normal	asserted	21	falling	normal
1	spi0-wifi-irq	GIO	in	normal	asserted	22	falling	normal
2		GIO	in	inverted	deasserted	23	any	normal
3	wifi-reset	GIO	out	normal	asserted	GIO	--	normal
4	spi0-wifi-cs	GIO	out	normal	asserted	GIO	--	normal
5		GIO	out	normal	asserted	GIO	--	normal
6		GIO	out	normal	asserted	GIO	--	normal
7	TNETV USB nreset	GIO	out	normal	asserted	GIO	--	normal
8		GIO	in	normal	deasserted	GIO	--	normal
9		GIO	in	normal	deasserted	30	any	normal
10		GIO	in	normal	deasserted	GIO	--	normal
11		GIO	in	normal	asserted	32	any	normal
12	GIO I2C SCL	GIO	in	normal	asserted	GIO	--	normal
13	GIO I2C SDA	GIO	in	normal	asserted	GIO	--	normal
14		GIO	in	normal	asserted	35	any	normal
15		GIO	in	normal	asserted	GIO	--	normal
16		CLKOUT0
17		VLYNQ RXD0
18		VLYNQ RXD1
19		VLYNQ RXD2
20		VLYNQ RXD3
21		VLYNQ_TXD0
22		VLYNQ TXD1
23		VLYNQ TXD2
24		VLYNQ TXD3
25		VLYNQ SCRU
26		VLYNQ CLK
27		GIO	in	normal	asserted	GIO	--	normal
28		GIO	out	normal	deasserted	GIO	--	normal
29	SPI-nSS	GIO	out	normal	asserted	GIO	--	normal
30		SPI SCLK1
31		SPI SDI1
32		SPI SDO1
33		CLKOUT1B
34		PWM1
35	GIO I2C SDA	GIO	in	normal	asserted	GIO	--	normal
36	GIO I2C SCL	GIO	in	normal	asserted	GIO	--	normal
37		GIO	out	normal	asserted	GIO	--	normal
38		GIO	out	normal	deasserted	GIO	--	normal
39		FIELD VENC
40		GIO	out	normal	deasserted	GIO	--	normal

I2C bus

Addresses available on I2c bus:

• 0x18 - Codec AIC3X
• 0x48 - Power Management TPS65021
• 0x58, 0x59, 0x5a, 0x5b, 0x5c, 0x5d, 0x5e, 0x5f - UNKNOWN
• 0x78, 0x79, 0x7a, 0x7b, 0x7c, 0x7d, 0x7e, 0x7f - UNKNOWN

TMS320 memory maps

Physical memory:

Region name	Description	Start	End	Size	Comments
DM320_RESET_VECTOR_PADDR	CPU reset vector	0x00000000	0x00000003	4 bytes	Should point to bootloader
DM320_IRAM_PADDR	CPU internal RAM	0x00000004	0x00003FFF	Approx. 16Kb
DM320_PERIPHERALS_PADDR	ARM peripherials registers	0x00030000	0x0003FFFF	4Kb
DM320_DSP_ONCHIP_RAM_PADDR	DSP internal RAM	0x00040000	0x0005FFFF	128Kb
DM320_AHB_PADDR	TMS320 internal AHB bus	0x00060000	0x00063FFF	4Kb
DM320_COPRO_SUB_PADDR	DMA coprocessor interface	0x00080000	0x0009FFFF	128Kb
DM320_EXT_MEM_PADDR	External memory	0x00100000	0x010FFFFF	16Mb	Maps to Flash exclusively (cached) Bootloader and kernel are stored here
DM320_CFI_PADDR	CFI Flash interface	0x40000000	0x40FFFFFF	16Mb
DM320_SSFDC_PADDR	SmartMedia interface	0x48000000	0x48FFFFFF	16Mb
DM320_CE1_PADDR	Control enable 1 (???)	0x50000000	0x50FFFFFF	16Mb	Related to Comm. port 1 (external interface)
DM320_CE2_PADDR	Control enable 1 (???)	0x60000000	0x60FFFFFF	16Mb	Related to Comm. port 2 (external interface)
DM320_VLYNQ_PADDR	VLYNQ interface	0x70000000	0x73FFFFFF	64MB	More details in http://en.wikipedia.org/wiki/VLYNQ
DM320_USBOTG_PADDR	USB On-The-Go inteface	0x80000000	0x800003FF	1Kb	More details in http://en.wikipedia.org/wiki/USB_On-The-Go

Virtual memory:

(..more to come..)

Flash:

Flash starts at 0x100000. Start and End values in table are absolute addresses.

Region name	Description	zsi_fw address	Start	End	Size	Comments
BOOT	rrload bootloader	N/A	0x00010000	0x00012000	64 Kb	Hardware write-protected
ENVIRO	Persistent variables	N/A	0x01000000	0x01007FFF	32 Kb	Bootloader variables (recoverzap, usbautoboot, etc.)
KERNEL	vmlinux kernel image	0x01008000	0x00120000	0x0031FFFF	2 Mb	Stock kernel image is about 1,6 Mb big
INITRD	initrd compressed ROM image	0x04400020	0x00320000	0x004FFFFF	1.875 Mb	At least 1,6 Mb big

Power managment

After loading the Linux kernel, the TPS 65021 is programmed via I2C (/usr/share/lua/5.1/pwrfix.lua) - devices' I2C address is 0x48.

• Device is set to PWM mode (register 0x04 = 10110010b).
• Core voltage set to 1.5V (register 0x06 = 00011100b).
• Codec and USB power line (LD02) to 1.8V, LCD display module (LD01) to 2.85V (register 0x08 = 00110110b).

HID (ATMEL MEGA165PV microcontroller)

The HID handles external devices - it is interfaced to the CPU via its built SPI interfase, clocked at 200 KHz.

This device is initialized on boot - the firmware loaded on it is located on /lib/clicky165.bin. The Fuse high byte register is set to 0xd1 (OCD and JTAG enabled, watchdog always on, uses reset vector), while the fuse low byte is set to 0xC2 (divide clock by 8, enable clock output, use clock source 1).

Once programmed, it accepts commands (via SPI) which are defined in /usr/include/hidif.lu. These are used to control & query external devices:

Name	Command	Description
CMD_SYNC	0xAA	Sync with device to send/receive Marks the beginning of a command
CMD_CLOSE	0xCC	Close sync Marks the end of a command
CMD_VER	0xBC
CMD_FILL	0xFF	Filler - seems to be used to signal HID that it can send data back
CMD_CODEC_RESET	0xD7	Reset codec
CMD_ADC_START	0xD8	Initalize ADC
CMD_ADC_RESULT	0xD9, 0xFFFF
CMD_SYS_CTRL	0xDA	Sends command SYS_CTRL_xxx
SYS_CTRL_POWEROFF	0x00	Powers off the Connect
SYS_CTRL_RESET	0x01	Reset the Connect
SYS_CTRL_SLEEP	0x02	Sleeps the Connect
SYS_CTRL_DIS_WD	0x03
SYS_CTRL_KICK_WD	0x4
SYS_CTRL_EN_HDQ_THERM	0x5
SYS_CTRL_EN_TS_THERM	0x6
SYS_CTRL_FRESET	0x80
CMD_SET_INTCHRG	0xD1
CMD_GET_INTCHRG	0xD2, 0xFF
CMD_SET_EXTCHRG	0xC6
CMD_GET_EXTCHRG	0xC7, 0xFF
CMD_GPIOD_SET_BANK	0xDB
CMD_GPIOD_SET_PORT	0xDC
CMD_GPIOD_GET_PIN	0xDF, 0xFF
CMD_GPIOD_SET_DDR	0xE0
CMD_HDQ_READ	0xC0	Read HDQ (battery) data
CMD_HDQ_WRITE	0xC1	Write HDQ (battery) data
CMD_HDQ_STATUS	0xC2, 0xFFFF	OK = 0, not ready = 1, timeout = 2
CMD_STATE	0xBB, 0xFFFFFFFFFFFFFFFF
CMD_PGMWAKE	0xBF
CMD_LCM_POWER	0xC9	Sends command LCM_xxx to LCD driver
LCM_POWER_OFF	0x00	LCD power off
LCM_POWER_ON	0x01	LCD power on
LCM_POWER_SLEEP	0x02	LCD sleep
LCM_POWER_WAKE	0x03	LCD wakeup
LCM_REPOWER_ON	0x04
CMD_WHEEL_EN	0xD0
CMD_MONOTIME	0xBD, 0xFFFFFFFF
CMD_MONORSTCNT	0xE4, 0xFFFF
CMD_SET_USBCHRG	0xE2
CMD_GET_USBCHRG	0xE3, 0xFF
CMD_GET_DOCK_STATE	0xE5, 0xFF
CMD_READ_DOCK_STATE	0xE6

Sync sequence is CMD_SYNC -> CMD_VER -> CMD_FILL -> CMD_CLOSE, while command sequence is CMD_SYNC -> command -> CMD_CLOSE -> CMD_FILL Communication to this device is handled by /usr/bin/hidtool, which is a binary file.

Device also seems to work as a watchdog.

Atmel AT88SC EEPROM and USB.

This device is read by the /bin/setupenv script - it retrieves both deviceid and MAC address and loads them into the $deviceid and $mac environment variables, respectively. Other environment variables (/etc/setupenv) are:

• Manufacturer:"SanDisk"
• Product name: "Sansa Connect"
• Vendor ID: 0x0781
• Product ID: 0x7480 (MTP more), 0x0F02 (Ethernet-over-USB mode), or 0x7482 (recovery mode)
• Product revision: 0x0101

Recovery Mode

Recovery Mode can be reached by completely powering down the device (by holding off for 10 seconds). Holding the volume-up and right keys while powering the device back on switch it to recovery mode. In recovery mode the device uses different USB IDs (0781:7481 and 0781:7482, vs 0781:7480 in normal operation) - if installed under Windows the Sansa Connect Device Recovery software will automatically launch when a Connect in recovery mode is connected.

USB ID 0781:7481 is used for writing .SRR files to Flash, while 0781:7482 acceses the "Zaprecover" service (complete with a kernel module!!!), which handles dumping files to the filesystem.

Once linux is loaded, recovery mode is signaled by a persistent variable ("recoverzap") stored in flash. This flag is only removed after a sucessful recovery operation, so there's no way to exit recovery mode once entered without running the recovery operation (and therefore wiping the unit) with the stock initrd file.

Recovery sequence

• Turn off the device completely (hold power key for 10 seconds)
• Turn the device on while holding volume-up and the right button (above the wheel)
• The device will boot showing a "recovery needed" indicator. On this mode the device exposes the USB ID 0781:7481, which zsi_fw.exe communicates to. This is NOT handled by linux - so it's either the linux bootloader or maybe even a previous instance of software. This mode is persistent after reboot.
• Once the USB cable is connected the indicator is changed to "recovery in progress".
• After a suceessful firmware load with zsi_fw.exe, the device will attempt to boot the vmlinux image (after a small delay). If the device reboots to recovery mode something went wrong with the firmware load. otherwise Linux will boot correctly and go to recovery mode, exposing the USB ID 0781:748 (Zaprecover service) and displaying a "starting recovery" message (with a yellow clock on top). How the device determines it has to go into recovery mode after boot is unclear - most likely it's because the flash filesystem is wiped after a firwmare write.
• Once a platform load is started with zaprecover.exe the message changes to_"receiving software"_.
• Once finished, the message now changes to "verifying software" (signature check), then "installing software" (a message reading _"can't find image_" might flash briefly). The device proceeds now to extract the platform into the filesystem.
• After a small delay, if everything went ok the device should now reboot to the familiar Sansa loading screen (with the five color balls).

ZAP recovery service

Once linux is loaded, on recovery mode the device loads a kernel module called "zaprecover" (/bin/usb_switch_zaprecover), listening on 0781:7482. The driver is interfaced with /usr/bin/zsi_zap, which tells the module how many files to expect and where to store them. On recovery mode, it waits for both the platform file and signature to be sent, in that order (/etc/rc.recover):

/usr/bin/zsi_zap -f /disk/zap/ZAP.tar.gz -f /disk/zap/ZAP.tar.gz.sig

The device won't leave recovery mode unless both files are downloaded correctly and the signature is checked. The data protocol used by the zaprecover service is still uknown, but the source for it is freely readable on the kernel patch.

Software

Original Software information can be found on SansaConnectOriginalFirmware.

Software/Hardware hacking

It is possible to replace the internal iNAND with microSD card - which allows to change the platform to for example start telnet. Tips: after connecting via wireless, stop WiFiThread to prevent disconnection due to inactivity, this can be achieved by checking the thread pid cat /var/tmp/native_thread_map, and then sending SIGSTOP to it(kill -s SIGSTOP pid).

JTAG

There is JTAG on the PCB. Hirose Electric FH19SC-16S-0.5SH(05) connector matches the footprint.

Connector pinout:

Volume up button

1    GND
2    RTCK (B1)
3    TDO (A13)
4    GND
5    TRST (F12)
6    TMS (A14)
7    TDI (B14)
8    TCK (C13)
9    GND
10   ? UNKNOWN
11   RXD0 (C2)
12   TXD0 (E5)
13   VDDIO (Vref for JTAG)
14   VDDIO (Vref for JTAG)
15   EMU0 (A2)
16   EMU1 (C3)

Volume down button

Vref is 3.3V. Bootloader configures UART0 to baud rate 115200, character format is 8N1, no flow control.

Free Software

The PDF that ships on the Sansa Connect CD includes a section called "Open Source Licences" and includes:

busybox
curl
Ezxml
Freetype
GPG
Linux
mDNSresponder
Mono
libpng
openssl
SSLeay
resample
Uclibc
wpa_supplicant
zlib

There are broken links in the PDF to the Sansa site to download modified source versions of the GPL licensed software. Instead these downloads are available from the Zing site, substituting zing.net for sandisk.com in the links: busybox, GPG, Linux, Mono, resample and Uclibc. Also attached is a diff created against the vanilla 2.6.4 kernel release.