2012-07-21

Teardown & review: A4Tech X-710 mouse

Inexpensive optical "gaming grade" mouse bought in 2006 (thus used for 6 years).
400/600/800/1000 dpi sensitivity, switchable while working and without driver needed.

Markings inside suggest that other mice from serie (X-708 to X-718) share same parts.
Steel 23 g weight (with X-708 mark).
It's little disappointing that only main switches (left and right button) are from OMRON.
Middle mouse button comes from Trantek Electronics.
After few years of usage both OMRON switches work flawlessly, but TTC switch had some problems as it was started to generate double clicks each time. Few drops of cleaning agent helped. Be careful and make sure it is dried before disassembling because mouse wheel (transparent plastic element) is not resistant to organic solvents.
Second problem (very common) comes from rotary mechanical switch that causes weird jumps when scrolling. Again, cleaning with organic solvents eliminates the problem (but it reappears after about 6 months, so this is not permanent solution). On the plus side mouse is easy to open and reassemble (no latches) so cleaning is quite fast. Petroleum jelly may work too and probably is safer to use.

Omron D2FC-F-7N are working reliably for me. In case of problem nice thing is they are serviceable: http://www.overclockers.com/forums/showthread.php?t=594646.


Optical sensor: Agilent ADNS-3060. According to datasheet it has selectable 400dpi / 800 dpi resolution, so I would suppose that other resolutions (including highest 1000 dpi) are interpolated. It seems to be common practice and some newer A4Tech mice (X-705, X-755, X-760, AK-47) share same sensor and their resolutions from 1000 dpi do 2000 dpi are interpolated.
It seems that X-718 and X-710 share same PCB, so some modding may be possible. "Upgrading" to X-718 would require either some simple PCB modification or - much more difficult because used MCU is not popular among amateurs/hobbyists - changing firmware or EEPROM data. Since even X-710 highest resolution already is interpolated it would give no real benefits in my opinion - it would give no more than changing mouse sensitivity in software. It would give one additional sensitivity setting (X-718 has 5 settings vs 4 settings in X-710), but if anyone actually using this feature that could also add more confusion when cycling through settings to go back to initial dpi. In my opinion two or three sensitivity settings would be optimal.
 Optical guide is also marked as Agilent.
Microcontroller: Elan EM78M611, 8-bit RISC with built-in USB low speed device. 6k x 13 bit program memory (1k erase cycles), 144 B SRAM, 4B (yes, 4 bytes!) EEPROM (4 k erase cycles), 24-channel 10 bit ADC. This microcontroller is dedicated for USB mice, keyboard and gaming controllers - one of it's features is automatic PS/2 / USB port detection allowing to use cheap passive USB to PS2 connector.
Most likely EEPROM is used to store selected by user dpi setting - I wonder if settings are stored each time they are changed by user what could cause problems with EEPROM life time.

2012-07-10

Teardown: M830BUZ

M830BUZ is a popular (due to very low price, usually ~$5) entry level digital multimeter. "BUZ" suffix stands for buzzer. Versions without buzzer are probably not worth buying as price difference is marginal if any. Unit disassembled here is over 12 years old (and still in good shape), branded as UNI-T.
Bubbles on the front sticker started appearing pretty quickly after purchase.
Heart of this multimeter is ICL7106 clone. In this unit chip is glued to additional PCB (branded UNI-T again) that has DIP-40 package size.
Dual operational amplifier (2904) is working as comparator activating buzzer and buzzer sound generator. Whole scheme is easy to find on the internet.
Rotary range switch would be probably critical component for device lifetime. I've saw over a dozen damaged multimeters of this type in RTV service and burnt switch traces (caused probably by accidental overvoltage / range error when servicing equipment) was common problem. Input protection is quite poor in this multimeter. Other possible problems are no auto power-off function (replacement battery costs about 20% of new multimeter) and hard to determine (random) quality of connection leads (mine survived over 5 years though). Of course additional features and high quality leads would not allow to keep price tag, so this have to be expected and acceptable at this price.


2012-07-07

Review: Sandisk Cruzer Blade 4GB USB drive

Cruzer Blade is one of the cheapest Sandisk USB drive. It has quite small plastic package. I suppose that two package pieces are clued together.

This unit was used for about two years - attached and detached one to two times per day. Plastic package seems to be problematic - it is splitting at the end. It also requires more force to plug and unplug to/from socket than typical steel connector making it easier to damage drive connector and - more importantly - socket itself (happened to me).
Drive speed is average in it's class (low-end).
USB descriptors dump:
Information for device Cruzer Blade (VID=0x0781 PID=0x5567): 
Version of TDD: 1.40 Date: Feb 23 2012 Time: 15:28:27

Connection Information:
------------------------------

Connection status: Device connected
Device actual bus speed: High 
Device is hub: No
Device adress: 0x0001
Current configuration value: 0x01
Number of open pipes: 2

Device Descriptor:
0x12 bLength
0x01 bDescriptorType
0x0200 bcdUSB
0x00 bDeviceClass   
0x00 bDeviceSubClass   
0x00 bDeviceProtocol   
0x40 bMaxPacketSize0   (64 Bytes)
0x0781 idVendor
0x5567 idProduct
0x0200 bcdDevice
0x01 iManufacturer   (SanDisk)
0x02 iProduct   (Cruzer Blade)
0x03 iSerialNumber   (3248131DDC511BAA)
0x01 bNumConfigurations


Device Qualifier Descriptor:
0x0A bLength
0x06 bDescriptorType
0x0200 bcdUSB
0x00 bDeviceClass   
0x00 bDeviceSubClass   
0x00 bDeviceProtocol   
0x40 bMaxPacketSize0   (64 Bytes)
0x01 bNumConfigurations 
0x00 bReserved 
Hex dump: 
0x0A 0x06 0x00 0x02 0x00 0x00 0x00 0x40 0x01 0x00 

Configuration Descriptor:
0x09 bLength
0x02 bDescriptorType
0x0020 wTotalLength
0x01 bNumInterfaces
0x01 bConfigurationValue
0x00 iConfiguration
0x80 bmAttributes   (Bus-powered Device)
0x64 MaxPower   (200 mA)

Interface Descriptor:
0x09 bLength
0x04 bDescriptorType
0x00 bInterfaceNumber
0x00 bAlternateSetting
0x02 bNumEndPoints
0x08 bInterfaceClass   (Mass Storage Device Class)
0x06 bInterfaceSubClass   (Transparent SCSI subclass)
0x50 bInterfaceProtocol   (Bulk only transport)
0x00 iInterface

Endpoint Descriptor:
0x07 bLength
0x05 bDescriptorType
0x81 bEndpointAddress   (In-Endpoint)
0x02 bmAttributes
   Transfer Type:           Bulk-Transfer
   Synchronization Type:    None
   Usage Type:              Data
0x0200 wMaxPacketSize   (512 Bytes) 
0x00 bInterval
Hex dump: 
0x07 0x05 0x81 0x02 0x00 0x02 0x00 

Endpoint Descriptor:
0x07 bLength
0x05 bDescriptorType
0x02 bEndpointAddress   (Out-Endpoint)
0x02 bmAttributes
   Transfer Type:           Bulk-Transfer
   Synchronization Type:    None
   Usage Type:              Data
0x0200 wMaxPacketSize   (512 Bytes) 
0x00 bInterval

Other Speed Configuration Descriptor:
0x09 bLength
0x07 bDescriptorType
0x0020 wTotalLength
0x01 bNumInterfaces
0x01 bConfigurationValue
0x00 iConfiguration
0x80 bmAttributes   (Bus-powered Device)
0x32 MaxPower   (100 mA)

Interface Descriptor:
0x09 bLength
0x04 bDescriptorType
0x00 bInterfaceNumber
0x00 bAlternateSetting
0x02 bNumEndPoints
0x08 bInterfaceClass   (Mass Storage Device Class)
0x06 bInterfaceSubClass   (Transparent SCSI subclass)
0x50 bInterfaceProtocol   (Bulk only transport)
0x00 iInterface

Endpoint Descriptor:
0x07 bLength
0x05 bDescriptorType
0x81 bEndpointAddress   (In-Endpoint)
0x02 bmAttributes
   Transfer Type:           Bulk-Transfer
   Synchronization Type:    None
   Usage Type:              Data
0x0040 wMaxPacketSize   (64 Bytes) 
0x00 bInterval

Endpoint Descriptor:
0x07 bLength
0x05 bDescriptorType
0x02 bEndpointAddress   (Out-Endpoint)
0x02 bmAttributes
   Transfer Type:           Bulk-Transfer
   Synchronization Type:    None
   Usage Type:              Data
0x0040 wMaxPacketSize   (64 Bytes) 
0x00 bInterval


Apart from delicate plastic package it wasn't causing any problems (unlike my previous Kingmax USB stick drive with USBest controller that got bricked multiple times and could not be permanently fixed with any tools I could find).
You can find some interesting information regarding this drive (and many other USB drives and SD cards) on  https://wiki.linaro.org/WorkingGroups/Kernel/Projects/FlashCardSurvey page. According to this page this model is using mix of SLC and MLC NAND cells for write optimization purposes. Quote:

This combines rather slow linear access with much faster random access. In case of the Cruzer blade, all data is first written in a 1 MB (or 1.33 MB) SLC erase block in log-structured mode, making it possible to overwrite directory entries, FAT or journal data at up to 20 MB/s. When a garbage collection is required, that small SLC erase block gets flushed back to an MLC erase block of 3 MB (or 4 MB), which is much slower, so writing linear data to multiple erase blocks can only sustain around 4-5 MB/s.

In overall, unless you are really tight on a budget I wouldn't recommend this USB drive model.