Wednesday, July 25, 2007

Speed Test part 2

Here is a speed test result at my office:

My Next-gen Phone Feature Wish List

Here I list features should be added to next generation phone:
  • Very good quality voice (it is still a phone, right?)
  • Very high speed data access (1 Mbps or more)
  • Very low latency data transmission. The low latency is supposedly to be used for VoIP (Skype-like thing wirelessly) and also for video streaming.
  • A web browser software with full support of flash, javascripts etc.
  • Software to read e-book/documents.
  • Able to play high quality music and support for OGG/Vorbis, besides MP3 (and get rid of the DRM. I super hate it!)
  • Video conference. with 25 fps rate (resolution is not important, but I don't want to see sluggish pictures or to many dropped frames either)
  • Power efficient.

Active Collision Avoidance System

Avionics is not something new today, but autonics (automotive electronics) is still an emerging technology. Although most cars made today use some kind of electronics/microcontroller, either for fuel injection, climate control system or others, the use of microcontroller still more to 'behind the scene' kind of application.

Some newer cars have limited passive collision-warning system. For example, Toyota Sienna XLE Limited. It has 8 infrared sensors, 4 are on the bumper at the front and another 4 at the back. Alarm will sound and warn the driver when distance is too close to the car (like this feature). Some others even add back up camera to see what is in the back through a LCD screen on the dashboard.

Passive collision-warning safety systems seek to reduce the risk of a collision by warning the driver of an impending risk so that he or she can take action to avoid the hazard.

There are many systems which provide warnings to the driver. The first warning systems available on production vehicles were typically "parking assist" type systems, which provide an audible tone when parallel parking and approaching a stationary object such as another vehicle or wall. Such systems have also been implemented in school buses, to detect crossing children who may be out of the driver's view. Today there are much more sophisticated systems which use radar and warn occupants of potential impending collisions under normal driving conditions. A passive collision-warning system is shown. As this diagram illustrates, a visual and/or audible warning is signaled to the driver, but there is no active intervention by the system to avoid a collision.

Image from book

Active safety systems take the collision-avoidance philosophy a stage further by interacting with the powertrain, braking, and even the steering systems. Every manufacturer appears to have a slightly different approach, but the common goal is to sense objects which present a collision risk with the host vehicle, then take preventive measures to avoid an accident. An active collision-avoidance system is shown below. The active system diagram shows that action without the immediate control of the driver is taken in order to avoid a potential collision.

Image from book

Advanced active collision systems use many clever techniques, over and above object detection, to ensure that a collision-avoidance event is facilitated safely and efficiently. For example, a sensor on the windshield can be used to detect the presence of rain and thus a potentially slippery road surface. In this case, the braking distance would probably be increased, so the hazardous object would have to be detected sooner. Likewise, tire-pressure sensors may be used to report the inflation level of tires, which could also have an effect on stopping distance.

It should be noted that although both the passive (collision-warning) and active (collision-avoidance) systems require object detection, there are differences in how the object detection system is implemented. The object detection performance of a collision-avoidance system must be higher and more robust than object detection for a passive system. It is unacceptable to execute an emergency braking maneuver under false-alarm circumstances. False alarms, while irritating for the driver, are generally considered more acceptable in collision-warning systems. Although the passive systems may allow false alarms more often, a more timely response by the sensor is required, as the reaction time of the driver must be taken into account in the event of an avoidance maneuver.

Sunday, July 15, 2007

Most Common and Generic PIC uC

The following is the best choice of PIC microcontroller for general purpose applications.
First, my criteria is a uC that is flash-based, cost-efficient, enough program space (>= 3 kB), has EEPROM, has I2C and SPI interface, programmable thru my PicKit2 programmer, has enough I/O pin (>= 8 I/O), has WDT, TTL-level voltage, low power usage, and able to communicate via asynchrononous serial port to PC. One of the most important thing is the PDIP availability, so I can develop it on my breadboard.

The intention of my future project is to develop home automation. The uC should be able to interface to sensors (thermal, humidity) as well as on-off microswitches (open-close sensors). It shall be able to communicate to my Linux PC via serial port, able to display status via 4x16 LCD display (Hitachi compatible) and still have some extra pins to do extra stuff (probably reading keypad, interfacing to darlington chip or LEDs).

Searched on MicroChip website (, I got this:

Chip: PIC16F690
Status = In Production
Volume Pricing = $1.20
Architecture = 8-bit (Harvard Architecture)
Program Memory = Standard
Type = Flash
KBytes = 7
KWords = 4
Self-write = NO
Data EEPROM = 256 bytes
RAM = 256 bytes
I/O = 18
ADC Channels = 12
ADC Bit = 10-Bit
ADC Sample Rate (ksps) = N/A
Comparators = 2
Timers/WDT = 2-8bit 1-16bit Yes
Interface = EUSART, I²C Compatible/SPI
Max. Speed MHz = 20
Int Oscillator (MHz) = 8
ICSP™ = Yes
ICD - # of Breakpoints = 1
CCP / ECCP = 0/1
PWM Channels = 4
PWM bits = 10
Parallel Port = No
Nanowatt = Yes
Vdd Min. = 2.2 V
Vdd Max. = 5.5 V
Pin Count = 20
Packages = 20/SSOP 208mil, 20/PDIP, 20/QFN, 20/SOIC 300mil

The unit price (PDIP only):

Part Number: PIC16F690-E/P
Lead Count: 20
Package Type: PDIP
Temp Range: -40C to +125C
Packing Media: Tube

1.75 *
1.67 *
1.59 *

Order Quantity:

Part Number: PIC16F690-I/P PIC16F690 view datasheet

Lead Count: 20
Package Type: PDIP
Temp Range: -40C to +85C
Packing Media: Tube

1.62 *
1.54 *
1.47 *

The "E/P" in part-number is to tell it is "Extended operational themperature" (Industrial standard). This might fit to auto-mobile applications, where operational voltage is more extreme than home application.