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hi all, iam a new to embedded programming and keil software. i am struck with a problem how to access a bit in a data buffer. the algo i need to implement is data_buf of 32 bits is stored in the micro controller. i need to send those bits bit by bit. ie. starting from bit 0 to bit 31. can anybody pls suggest me how to write a program in keil. thanks in advance uday
hi, i did not ask to teach me bitwise operators mr. andrew. if u had not read the mail sent by me properly, i repeat it again. i have declared a buffer holding a 32 bit value. i need to send that value on 3rd pin of port 0. my problem was how to access each bit of the buffer and send it. if i use a piece of code below..is it correct ? /********** unsigned int data_buf[40]; unsigned int i; for (i=0;i<=39;i++) { P0^3 = data_buf[i]; } *********/ hope iam now clear in explaining the problem. thx uday
"i did not ask to teach me bitwise operators mr. andrew." True; I'm just suggesting that you can achieve your aim by using the standard ANSI 'C' bitwise logical operators (let's call them "mask" operators if it helps) and the standard ANSI 'C' shift operators. You didn't answer whether you're already familiar with 'C', so Look them up in your 'C' textbook, if necessary. Then think about what you're trying to achieve, what the operators do, and thus how to proceed. "i have declared a buffer holding a 32 bit value." No you haven't:
unsigned int data_buf[40];
P0^3 = data_buf[i];
/********** comment starts here unsigned int data_buf[40]; unsigned int i; for (i=0;i<=39;i++) { P0^3 = data_buf[i]; } *********/ comment ends here!
i have declared a buffer holding a 32 bit value. i need to send that value on 3rd pin of port 0. my problem was how to access each bit of the buffer and send it. if i use a piece of code below..is it correct ? /********** unsigned int data_buf[40]; unsigned int i; for (i=0;i<=39;i++) { P0^3 = data_buf[i]; } *********/ No. This code will not work and does not match the description you provided. Ignoring the fact that the code is commented-out, even still it will not work. i have declared a buffer holding a 32 bit value. No, you have declared an array of 80 bytes (40 ints). Since bytes have 8-bits, your buffer holds 640 bits (not 32). i need to send that value on 3rd pin of port 0. OK, then why do you send 40 bits when your first sentence says you have 32 bits. my problem was how to access each bit of the buffer and send it. This is what Mr. Neil suggested with his comment to "look at the shift and bitwise operators." Have you looked at any of the example programs provided or looked into the 8051 download files ( http://www.keil.com/download/c51.asp)? There are several examples there that do similar things to what you want. Jon