Navaidstech
- 11th March 2009, 03:17
Hi all...
OK, OK... I realize that the Manchester topic has been beaten to death here. I promise you that I've read pretty much every post on it but I still have questions and I hope some of you will steer me in the right direction.
Here is the deal: I'm trying to design a wireless link between two PIC devices using a 433 MHz RF module. Device1 will be sending information such as temperature, garage door status, garage lights status, etc, to Device2.
Initially I was going to make life simple and modulate the RF TX by a PIC serial port and send out your typical ASCII type data, but then I stumbled across some information on the benefits of Manchester coding and decided to go with that instead.
Since I have an abundance of 16F84 and 16F628 chips, I'd prefer to concentrate on those as much as possible.
Here are some of the questions that linger:
1. I've noticed some examples here make use of HSEROUT/HSERIN commands. I tried writing the code using these and the program (Microcode Studio with PBP) would not compile it. Subbing these commands for SEROUT/SERIN eliminated these problems. I'm assuming my chips do not support these commands. Am I correct?
2. OK...old school thinking here. Since each Manchester data word is 16 bits long.... how do I send it out of the PIC that has a start, 8 data byta, stop , parity bits? Some examples here were using SEROUT2 as opposed to SEROUT command and I did some research on those in the Microcode Help file. Am I correct in assuming that SEROUT2 allows to transmit longer data and is not limited to just 8 bits?
3. I understand that one needs to send out a preamble allowing the receiver to stabilize before it accepts good data. Does the preamble need to be sent out before every data word, or just at the beginning of the entire data sequence?
If the latter, how does the receiver distinguish between each data word, other than couting the incoming bits? Would it be wise to insert some sort of a control character in front of each data word so the receiver has better time separating one data word from the next?
I think this is it for now. I'm sure there will be more questions but these three should be enough to get me started.
Any help would be greatly appreciated.
Thanks!
Alex
OK, OK... I realize that the Manchester topic has been beaten to death here. I promise you that I've read pretty much every post on it but I still have questions and I hope some of you will steer me in the right direction.
Here is the deal: I'm trying to design a wireless link between two PIC devices using a 433 MHz RF module. Device1 will be sending information such as temperature, garage door status, garage lights status, etc, to Device2.
Initially I was going to make life simple and modulate the RF TX by a PIC serial port and send out your typical ASCII type data, but then I stumbled across some information on the benefits of Manchester coding and decided to go with that instead.
Since I have an abundance of 16F84 and 16F628 chips, I'd prefer to concentrate on those as much as possible.
Here are some of the questions that linger:
1. I've noticed some examples here make use of HSEROUT/HSERIN commands. I tried writing the code using these and the program (Microcode Studio with PBP) would not compile it. Subbing these commands for SEROUT/SERIN eliminated these problems. I'm assuming my chips do not support these commands. Am I correct?
2. OK...old school thinking here. Since each Manchester data word is 16 bits long.... how do I send it out of the PIC that has a start, 8 data byta, stop , parity bits? Some examples here were using SEROUT2 as opposed to SEROUT command and I did some research on those in the Microcode Help file. Am I correct in assuming that SEROUT2 allows to transmit longer data and is not limited to just 8 bits?
3. I understand that one needs to send out a preamble allowing the receiver to stabilize before it accepts good data. Does the preamble need to be sent out before every data word, or just at the beginning of the entire data sequence?
If the latter, how does the receiver distinguish between each data word, other than couting the incoming bits? Would it be wise to insert some sort of a control character in front of each data word so the receiver has better time separating one data word from the next?
I think this is it for now. I'm sure there will be more questions but these three should be enough to get me started.
Any help would be greatly appreciated.
Thanks!
Alex