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good day fellow engineers..
i’ve got a big problem with my project. it’s dealing with sending AT commands from my PIC18F4550 to my Sony Ericsson K700i using UART..
my first problem is how to make a circuit that will have my PIC tx to output 3V? since my Cellular Phone can only recieve a maximum of 3V.. will i need a MAX232 circuit? or just simply a Zener diode circuit?
and my second problem is that how can i convert PDU format to ASM format? since my phone only accepts PDU format..
plss help me..
thx everyone!..
You need to use 5v to 3V level shifter IC. I don’t think it can be done with something like zener diode, because the voltage corresponding to logic 0 and logic 1 are different in 3v-logic and 5v-logic.
You need to use 5v to 3V level shifter IC. I don’t think it can be done with something like zener diode, because the voltage corresponding to logic 0 and logic 1 are different in 3v-logic and 5v-logic.
Hi Billy,
No need of using MAX232 IC.If your controller source voltage is more than 3.3V then use SN74LVC4245A bidirectional voltage level translator in between your controller and phone to communicate.
Regarding PDU format, you need to decode the received message fom PDU format, this can be done in coding.
Suggest you to go through the PDU format & understand the bit by bit data.
Example:
PDC CODE: 0891683108200805F01151048181160000FF16C8329BFD66B5F320B8BC4CA7E741F7B79C4D0E01
08: Length of Service Center Number
91: Indicate there is a plus at the beginning of Service Center number
683108200805F: Service Center number: 8613800280500 Note when the length
of number is an odd number, add F.
11: Indicate this SMS will be sent.
51: TP-MR Message Reference, not common used.
04: Length of destination number. Here 1861.
81: No plus here.
8161: Destination number 1861.
00: TP-PID.
00: TP-DCS. TP-UD is coded by 7bit character method.
FF: TP-VP. Valid Period. Here is infinity.
16: Hex value equals to 22. This indicates there are 22 characters in TP-UD
C8329BFD66B5F320B8BC4CA7E741F7B79C4D0E01: TP-UD, decode it using 7bit character method.
Any more info needed kindly post.
Hi Billy,
No need of using MAX232 IC.If your controller source voltage is more than 3.3V then use SN74LVC4245A bidirectional voltage level translator in between your controller and phone to communicate.
Regarding PDU format, you need to decode the received message fom PDU format, this can be done in coding.
Suggest you to go through the PDU format & understand the bit by bit data.
Example:
PDC CODE: 0891683108200805F01151048181160000FF16C8329BFD66B5F320B8BC4CA7E741F7B79C4D0E01
08: Length of Service Center Number
91: Indicate there is a plus at the beginning of Service Center number
683108200805F: Service Center number: 8613800280500 Note when the length
of number is an odd number, add F.
11: Indicate this SMS will be sent.
51: TP-MR Message Reference, not common used.
04: Length of destination number. Here 1861.
81: No plus here.
8161: Destination number 1861.
00: TP-PID.
00: TP-DCS. TP-UD is coded by 7bit character method.
FF: TP-VP. Valid Period. Here is infinity.
16: Hex value equals to 22. This indicates there are 22 characters in TP-UD
C8329BFD66B5F320B8BC4CA7E741F7B79C4D0E01: TP-UD, decode it using 7bit character method.
Any more info needed kindly post.
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