Interview Q&A

Blue Tooth

• Why is Bluetooth called a cable replacement technology?- Bluetooth technology allows the creation of Personal Area Networks without cables or wires that are usual in home networks. 
• Give a generic description of Bluetooth? - Bluetooth is a low-cost, short-range (RF) links between mobile PCs, mobile phones and other portable devices. Bluetooth can transmit through solid, non-metal objects. 
• Why can Bluetooth equipment integrate easily in TCP/IP network? - Because Bluetooth uses wireless LAN standards IEEE for data transmission. 
• Is it possible to connect multiple Bluetooth hubs? - No, only one hub can be used at a time with a computer. USB or Serial devices can be added.  
• What is FCC and how does it relate to Bluetooth? - FCC is Federal Communication Commission, which issues licenses to the stations for specific frequencies. It also decides who is able to use which frequency for what purpose. Since Bluetooth is using unlicensed spectrum, FCC has no direct involvement with Bluetooth 
• Under what frequency range does Bluetooth work? - 2.45 GHz is the frequency range. 
• Do Bluetooth devices need line of sight to connect to one another? - No. 
• Which technology is used in Bluetooth for avoiding interference? - Frequency hopping is the technology used in Bluetooth. 
• Bluetooth signals do not interfere with our PCs or cordless phones or portables. Why? - Bluetooth uses low-power signals, it plays around in 2.45 GHz range, while most of consumer devices would be using 900 MHz. 
• What is Airport? - Airport is a wireless communications system, like Bluetooth. It is based on the IEEE 802.11 recommendation. It also uses 2.4 GHz frequency band, but its range is about 45 meters and it boasts a transmission speed of 11 Mbit/second. It is developed by Lucent Technologies. 
• What is Piconet? - A collection of devices connected through Bluetooth technology in an ad hoc fashion. 
• What are the three main types of connection used by Bluetooth? - Single slave, Master slave, Scatternet . 
• What is FEC in Bluetooth? - Forward Error Correction is a method by which Bluetooth increases its noise immunity. FEC is a method that enables a receiver to not only detect, but also correct errors in a transmission. 
• Which method is primarily used for Voice transfer? - Synchronous Connection Oriented (SCO) is a method primarily used for Voice transfer. 
• What is the frequency range used for Bluetooth in Europe and United States? - 2402 MHz to 2480 MHz are the frequency ranges used in USA and Europe. 
• List some Technology characteristic of Bluetooth? - Omni directional, Adaptive output power to minimize interference, Support Synchronous & asynchronous services, Fast Frequency Hopping to avoid interference, Short data packets to maximize capacity during interface. 
• Which company originally conceived and developed Bluetooth? - Ericsson. 
• How does Bluetooth use frequency hopping for security? - Bluetooth picks a random frequency out of 79 and then hops around the range about 1600 times per second. 
• What is a Bluetooth dongle? - A device that hangs outside of a computer, or phone to provide Bluetooth connection. 
• What are the other (competing or not) wireless technologies? - Wi-Fi, IrDa, EDGE, UWB (Ultra Wide Band) 
• Which Bluetooth version uses adaptive frequency hopping? Why? - In Version 1.2 Adaptive frequency hopping method is used, which improves resistance to radio interference, and provides higher transmission speed. 
• How many SCO links are there in a piconet? - In a piconet, there can be up to three SCO links of 64,000 bits per second each. 
• what is the total number of masters and slaves in a piconet? - 1 Master and 7 Slaves. 
• Which method is used for Data transfer? - Asynchronous Connectionless (ACL) is Data transfer method in Bluetooth 
• What is the frequency range used for Bluetooth in Japan? - 2472 to 2497 MHz is the frequency range used for Bluetooth in Japan. 
• What is the strength of the signal transmitted by powerful cell phones? - The powerful cell phones can transmit a signal of 3 watts.

C and C++

What is an inline function? 
How are macros different from functions? 
In embedded systems perspective which is better to use. Macro or function? 
What is a volatile keyword? How it helps in the embedded perspective? 
How ISR is serviced? 
What is interrupt latency? 
What are the stages of compilation? 
What is booting? 
What is PID? 
What is hysterysis? 
Co-relation between pointers and arrays? 
If A and B finishes a work in 5 days. Where is does the work twice that of B. Suppose they finished the work in 3 days and B is doing the work normally then at what rate should A work to finish the work in 3 days? 
if(x)

  y=a;

else

  y=b;

 For x=0, 1 evaluate a expression satisfying the above condition?
What is a constant pointer? 
What is a memory leak in structures? How can we rectify that? 
When the execution id going to service a interrupt what happens to stack and what are the registers saved? 
Without using pointer write a program to print the elements of an array? 
How are unions useful in embedded systems? 
What is optimization? 
How many pins are used in SPI? What are they? 
Explain the Start and Stop operation of I2C protocol? 
Is it possible to access or modify PC (program counter)? 
If int data type is occupying 4 bytes then on how many bit uC does the code is running? 
Is C++ a superset of C? 
All C programs are executable in C++? True or False Why? 
What is a static storage class? How is it useful? 
How static is different from auto?

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