RS-232 to 100 MHz RF desktop channel adapter
Notice: This section describes an experimental low power, low bandwidth data signaling system that operates at 100 MHz (In the FM broadcast band in the U.S.). Before operating a radio transmitter, find out what kind of transmitter operation, if any, is permitted in your locality. Radio transmitter operation is a serious legal matter. In the United States, operation of unlicensed intentional radiators is covered by Part 15 of Title 47 of the Code of Federal Regulations. This design can be readily adapted to different frequencies and different power levels. If you choose to build and operate the transmitter described here, you do so at your own risk. I'm only publishing this as an example of what can be done, and to show how easy it is to build a simple but functional receiver.
Link to Site: http://cappels.org/dproj/232LINK/232link.htm
Notice: This section describes an experimental low power, low bandwidth data signaling system that operates at 100 MHz (In the FM broadcast band in the U.S.). Before operating a radio transmitter, find out what kind of transmitter operation, if any, is permitted in your locality. Radio transmitter operation is a serious legal matter. In the United States, operation of unlicensed intentional radiators is covered by Part 15 of Title 47 of the Code of Federal Regulations. This design can be readily adapted to different frequencies and different power levels. If you choose to build and operate the transmitter described here, you do so at your own risk. I'm only publishing this as an example of what can be done, and to show how easy it is to build a simple but functional receiver.
Link to Site: http://cappels.org/dproj/232LINK/232link.htm
| CODE |
;****************************************************** ;Send and receive FM data, pass through UART at 9600 baud ;****************************************************** .include "2313def.inc" ; memory index =r0; used for fetching strings from memory .def bitsout = r02; counter for bits sent (couple also use a delay counter) .def sendheader = r03;headerr to place on outgoing RF byte .def receiveaddress = r04; Address mask for RF received data header .def temp = r16; Scratch register. .def tcounter = r17 ; 8 Bit loop timing counter. .def delaycounter = r18; Delay to increase time measureble with 8 bit tcounter. .def runincount = r19; Used to keep track of consecutive zeros detected in runin code. .def wirelessdat = r19; data to be sent via wireless port ;REGISTER 19 USED TWICE ON PURPOSE .def inbyte = r20; Decoded data byte could be same register as runincoung .def header = r21 .def outbyte = r21;Byte value to be sent (input to send routine) ;REGISTER 21 USED TWICE ON PURPOSE .equ minzeros = 9;Minimum number of consecutive zeros to qualify as run-in code .equ defaultsendheader = $10;Default value of RF sendingheaderr. .equ defaultreceiveaddress =$02;Default value for RF receiveing address in header .equ RFxmitdat = 5 Port bit used to send transmit data to RF transmitter .equ RFrcvdat = 6 Port bit used to receive data from RF receiver ;SETTING UP THE UART .equ clock = 4000000 ;clock frequency .equ baudrate = 9600 ;choose a baud rate .equ baudkonstant = (clock/(16*baudrate))-1 ; Used for memory index = ZL,ZH ;PORT D ; bit 0 this pin used for UART RX pin ; bit 1 this pinused for UART TX pin ; bit 5 Send data to RF transmitter ; bit 6 receive data from RF receiver ;EEPROM ;0 not used ;1 sendheader ;2 receiveaddress .cseg .ORG $0000 ;START INITIALIZATION ldi temp,low(ramend) out spl,temp ;Set the 8 bit stack pointer to the top of ram. ldi temp,baudkonstant;load baud rate into the UART out ubrr,temp cbi PORTD,RFrcvdat;no pullup on receiver input cbi DDRD,RFrcvdat;make receier input pin an input cbi PORTD,RFxmitdat ;initial state of transmitter output is low sbi DDRD,RFxmitdat;make transmitter output pin an output ; ldi temp,defaultsendheader;Establish the default RF sendingheaderr ; mov sendheader,temp ;88888TEMPRORAILLY COMMENTED OUT!!!!!!!!!!!! ;Fetch default transmit address from EEPROM ldi temp,$01 out eear,temp ;Set up the read address sbi eecr,eere ;Trigger the read in temp,eedr ;Get the data into temp mov sendheader,temp ;Fetch default receive address from EEPROM ldi temp,$02 out eear,temp ;Set up the read address sbi eecr,eere ;Trigger the read in temp,eedr ;Get the data into temp mov receiveaddress,temp ; mov receiveaddress,temp ;Put it into receiveaddress register. sbi ucr,rxen;enable UART receive function ;FINISHED WITH THE INITIALIZATION ;SEND GREETING rcall greeting main:;MAIN FOREGROUND LOOP FOR THIS MACHINE rcall rsreceiveit;Check for RS-232 data coming in and send via RF link if anything's ready rcall rssendit ;Check for incoming RF data. If coming in, decode and send to RS-232 device. rjmp main rsreceiveit:;CHECK FOR DATA FROM TERMINAL. IF PRESENT, RESEND IT. Trap and intrepret Escape sequences. sbis usr,rxc ;wait for data rjmp norsdata in wirelessdat,udr ;read data cpi wirelessdat,$1B ;See if this is an escape character. brne NotEscapeCommand;If it keep going as if nothing happened -skip to bottom receivecommand: ;If that was an Escape, then wait for command. sbis usr,rxc ;wait for data rjmp receivecommand in wirelessdat,udr ;read command andi wirelessdat,$DF ;And with $DF to make ASCII upper-casce. receiveparameter: ;Receive the parameter sbis usr,rxc ;wait for data rjmp receiveparameter in temp,udr ;Read parameter (interpreded as in the range of 0..7). subi temp,$30 ;Then make into address to insert into the header. andi temp,$07 lsl temp lsl temp lsl temp mov bitsout,temp ;Store results in bitsout for now. ;Now interpret the command cpi wirelessdat,$54 ;"T" set transmit address brne NotTransmit mov temp,bitsout mov sendheader,temp ;Store the address wrat: sbic eecr,eewe ;Wait for EEPROM write to not be busy rjmp wrat ldi temp,$01 out eear,temp ;Set up the write address mov temp,sendheader out eedr,temp ;Set up the write data sbi eecr,eemwe sbi eecr,eewe ;Trigger the write NotTransmit: cpi wirelessdat,$52 ;"R" set receive address brne NotReceive mov receiveaddress,bitsout;Put the number in the address receive register wrar: sbic eecr,eewe ;Wait for EEPROM write to not be busy rjmp wrar ldi temp,$02 out eear,temp ;Set up the write address mov temp,receiveaddress out eedr,temp ;Set up the write data sbi eecr,eemwe sbi eecr,eewe ;Trigger the write NotReceive: ret ;End of processing escape. NotEscapeCommand: ; com wirelessdat ;///////////////////TEST ONLY INVERTED DATA if not commented out/////////// rcall sendabyte norsdata: ret rs_send: ;SEND CONTENTS OF TEMP VIA SERIAL PORT sbi ucr,txen ;set sender bit sbis usr,udre ;wait till register is cleared rjmp rs_send out udr,temp ;send the contents of temp. cbi ucr,txen ;clear sender bit ret ;go back sendstring: ;call with location of string in Z lpm ; Load byte from program memory into r0 tst r0 ; Check if we've reached the end of the message breq finishsendstering ; If so, return mov temp,r0 rcall rs_send adiw ZL,1 ; Increment Z registers rjmp sendstring finishsendstering: ret greeting: ldi ZH,high(2*gteetingmessage) ; Load high part of byte address into ZH ldi ZL,low(2*gteetingmessage) ; Load low part of byte address into ZL rcall sendstring ; sent it. mov temp,sendheader ;display defualt transmit address andi temp,$78;mask off all but the address lsr temp;shift to right to make address into a binary number lsr temp lsr temp ori temp,$30;make into an ascii number rcall rs_send ldi ZH,high(2*greetingsecondpart) ; Load high part of byte address into ZH ldi ZL,low(2*greetingsecondpart) ; Load low part of byte address into ZL rcall sendstring ; sent it. mov temp,receiveaddress ;display defualt receive address andi temp,$78;mask off all but the address lsr temp;shift to right to make address into a binary number lsr temp lsr temp ori temp,$30;make into an ascii number rcall rs_send ;print some blank lines ldi ZH,high(2*crlfs) ; Load high part of byte address into ZH ldi ZL,low(2*crlfs) ; Load low part of byte address into ZL rcall sendstring ret gteetingmessage: .db $0A,$0D .db "RF interface. 02JUN2002 Dick Cappels." .db $0A,$0D .db "To change receive address, type <ESC>, R, <Address> " .db $0A,$0D .db "To change transmit address, type <ESC>, T, <Address>" .db $0A,$0D .db "Where the valid range of address is 0..7" .db $0A,$0D .db "Default transmit address is set to = $0" .db $00,00 greetingsecondpart: .db $0A,$0D .db "Default receive address is set to = $0" .db $00,00 crlfs: .db $0A,$0D .db $0A,$0D .db $0A,$0D .db $00,00 ;///////////////////////////////////////////////////////////////////////////////////////////////////// rssendit:;CHECK FOR DATA FROM RADIO RECEIVER AND IF PRESENT, SEND TO TERMINAL rcall TryToGetbytemessage; returns with header in header and data in inbyte andi header,$78 ;mask off all but the address part of the header cp header,receiveaddress ;check the header to see if header matches address brne notforme ;if not for address $01 then don't send it on. mov temp,inbyte ;if it is addressed tho this machine then send it on to terminal waittosend: sbi ucr,txen;set sender bit sbis usr,udre;wait till register is cleared rjmp waittosend out udr,temp;send the recived data cbi ucr,txen;clear sender bit notforme: ret ;///////////////RADIO RECEIVE BYTE ROUTINES/////////////////// ;Try and decode a valid header and data byte. In the case or error, return with header = $00 ErrorQuitReceiving: ldi header,$00 ret TrytoGetbytemessage: ldi header,$00 ldi temp,$00 mov runincount,temp GetAnotherZero: ;Start of loop to gather minzeros zeros in runin code. rcall Getbit brts ErrorQuitReceiving;It Getbit comes back with T set, its an error; start over. brcs ErrorQuitReceiving;If Getbit comes back with carry set, its a one, not a zero -start over inc runincount cpi runincount,minzeros brmi GetAnotherZero WaitForStartbit: ;Start of loop waiting for a one, which will be the start bit. rcall Getbit brts ErrorQuitReceiving;It Getbit comes back with T set, its an error; start over. brcc WaitForStartbit;If its a zero, keep looking ;OK, Now we have the start bit, so the next 8 bits will be the header. Shift them in. ldi temp,$08 mov runincount,temp Getheader: rcall Getbit brts ErrorQuitReceiving;It Getbit comes back with T set, its an error; Stop receiveing. rol header ;Shift new bit into header byte dec runincount brne Getheader;If all bits aren't in yet, go get another. ;At this point, one could tell whether this data is addressed to this machine, but I am going to leave ;address qualification to another part of the code. If time were very precious, one could stop ;execution of this part of the receive routine right here. rcall Getbit ;Throw this one away. Its the start bit for the next byte ;It must be here so two bytes of zeros can't look like ;the runing code. brts ErrorQuitReceiving;It Getbit comes back with T set, its an error; start over. ;Now we have the runinbits, the start bit, and the header. Next is the data. Shift it in. ldi temp,$08 mov runincount,temp GetInbyte: rcall Getbit brts ErrorQuitReceiving;It Getbit comes back with T set, its an error; Stop receiveing. rol inbyte ;Shift new bit into input data byte dec runincount brne GetInbyte;If all bits aren't in yet, go get another ret ;RETURN WITH header IN header AND DATA IN INBYTE Getbit: ;Subroutine to get a received bit. ;It returns the value of the received bit in the carry bit ;If this routine does not receive a valid data bit IT WILL NOT RETURN. ;If it is necessary to recover from this situation, the watchdog timer can be used. ;It measures the time between rising edges on the input pin (B3 originally). ;Successfult bit decoding will return with T flag clear. T flag =1 means error. ldi tcounter,$00 ;Zero the counter. ;Count, waiting for pin to go low. WaitForLow: ldi delaycounter,$16;load with $16, 1 cycle takes 17.5 us delayloop1: dec delaycounter brne delayloop1 inc tcounter breq nobit sbic PIND,RFrcvdat rjmp WaitForLow ;Continue to count, waiting for pin to go high. WaitForHigh: ldi delaycounter,$16 delayloop2: dec delaycounter brne delayloop2 inc tcounter breq nobit sbis PIND,RFrcvdat rjmp WaitForHigh ;Determine if we measured a "legal" bit and if so wheter it as a one of a zero. ;pcode: ;If tcount < $42 start over ;If tcount <$6E its a one ;If tcount is < $84 start over ;If tcount is >$DC start over ;Else, its a zero cpi tcounter,$42 brmi nobit cpi tcounter,$6E brmi ItsAOne cpi tcounter,$84 brmi nobit cpi tcounter,$DC brpl nobit ;If it gets here, its a valid zero.; clt ;Clear T flag (no error), set the carry bit to show that its a zero and return. clc ret ItsAOne:clt ;Clear T flag (error) set carry flag (data is a one), and return. sec ret nobit: ;Error receiving a bit, set T flag and leave set ret ;/////////////////////////RADIO SEND BYTE ROUTINES///////////////////////// Sendabyte: ;SEND RUNIN CODE (16 ZEROS) ldi outbyte,$00 ;get ready to send 16 zeros ldi temp,$0F ;$0F databits plus a zero "start bit" mov bitsout,temp clc ;no start bit (it goes as another zero) rcall LateTransmitAByte;jump into byte sending routine ;Send the header byte. The first and last bit in the headder is always a "1". Its the law. mov outbyte,sendheader rcall TransmitAByte ;(Ok, now the 16 bits of runin, the start bit, and the 8 bits of header have been sent. ;Time to send the data byte. mov outbyte,wirelessdat rcall TransmitAByte ldi outbyte,$FF ;get ready to send 1 one, channel idle, to finish the last data bit. ldi temp,$02 ;$01 databits plus a start bit mov bitsout,temp sec ;no start bit rcall LateTransmitAByte;jump into byte sending routine ret ;finished sending the one byte message TransmitAByte:;send a byte out the wireless port ldi temp,$09 mov bitsout,temp sec;start bit is a "one" LateTransmitAByte: SendACycle:;a one or a zero, depending on the state of carry bit sbi PORTD,RFxmitdat ldi tcounter,$00 ldi delaycounter,$04 brcs notazero1 ldi delaycounter,$08 notazero1: Delay: dec tcounter brne Delay dec delaycounter brne delay cbi PORTD,RFxmitdat ldi tcounter,$00 ldi delaycounter,$04 brcs notazero2 ldi delaycounter,$08 notazero2: Delay2: dec tcounter brne Delay2 dec delaycounter brne delay2 rol outbyte;sent start bit and all 8 data bits yet? dec bitsout brne SendACycle;if not send another bit ret ;//////////END OF CODE FOR SEND ROUTINE/////////////// |