Microcontrollers & Embedded System Designs

Some Tips!

So now everything is clear I hope. We have discussed just the SMS related functions of the FBUS because that was all we needed. You can check www.gnokii.org for more information on other features like Call-handling, Battery-monitoring to name a few.
·        We had started with using the AT89S52 controller which has the limitation of RAM size (256 bytes).All the frames are received in this RAM of which half may be used for stack operations, registers etc.
You have seen that a mere ‘hello’ frame is 58 bytes long. Some more declarations will require using RAM, so more and more of RAM is used. In such a case what if a really long SMS is received?
 No need to panic! Simply delete such an SMS without taking any action.   Subsequently all that needs to be taken care of are the actual SMS we are going to consider or have stored in our code memory!
People have therefore used AVR controllers for this. Incidentally you can use external EEPROM for the 52 controller as well. However using the S52 is simpler and serves the purpose of only switching devices on/off
·        We have not discussed anything about the Battery connections and charging it. You cannot remove the battery and connect +5V directly to the battery terminals. The battery has some electronics built in to identify type of battery and temperature of battery. Elaborately what you can do is design a charger which switches off when battery is fully charged (nokia battery chargers are CV chargers and have no electronics to cut off power on full charge)
·        The above method is tedious and a simpler way exists. Take an old nokia battery, disassemble it. Now connect your power supply +5V to the B+ and Gnd to B- terminals.
·        Power Supply should be able to deliver up to 3A max

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Fig 1.5 Disassembled Battery

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