Full Duplex Serial Object documentation
William50
Posts: 22
I want to communicate at 38400 baud and I understand that the Full Duplex Serial Object can handle this.
The source code for this object does not include comments. Is there a documentation file that describes its code?
The source code for this object does not include comments. Is there a documentation file that describes its code?
Comments
''************************************ ''* Full-Duplex Serial Driver v1.1 * ''* (C) 2006 Parallax, Inc. * ''************************************ '' '' '' Added Notes from: Mike Green, lifted from: http://forums.parallax.com/forums/default.aspx?f=25 '' '' "FullDuplexSerial" is a full duplex serial driver. It uses only one cog to both transmit and receive. '' You only need to call the start routine once to set up both directions. To use pin 0 for transmit and '' pin 1 for receive at 9600 Baud you'd call "serial.start(1,0,%0000,9600)". That implies Rx not inverted, '' Tx not inverted, not open drain on transmit, and no ignore echo on receive. This assumes that you declare '' 'OBJ serial : "FullDuplexSerial"'. '' '' The return value is true if the driver was started ok, false if there were no free cogs available (rarely happens). '' '' FullDuplexSerial is intended to provide a buffered high speed serial communications channel in both directions '' at once using a single cog. '' '' The actual UART function in the FullDuplexSerial object resides in a cog (for each full duplex channel). This '' does the actual "bit-banging" and does the manipulation of the I/O pins. It communicates with the "interface" '' routines written in SPIN by means of transmit and receive buffers declared in the FullDuplexSerial object. '' The interface routines (like .tx, .rx, .rxcheck) can be called from any cog running SPIN although, if you try '' to receive or transmit from more than one cog at a time, you'll get into trouble since both cogs will try to '' put data into or get data out of the same buffer at the same time. The fix for this is to use the semaphores '' (LOCKxxx). It would be unusual to have to do this. Normally, only one cog would make use of any one full duplex '' channel. '' '' The FullDuplexSerial routines should work to at least 384 kB '' '' VAR long cog 'cog flag/id long rx_head '9 contiguous longs long rx_tail long tx_head long tx_tail long rx_pin long tx_pin long rxtx_mode long bit_ticks long buffer_ptr ' transmit and receive buffers ' buffers need to be a power of 2; ie: 16 32 64 128 256 512 ' Note: looks like the maximum size of the buffer can only be 512 bytes. byte rx_buffer[noparse][[/noparse]256] ' <----------- Change Buffer Size Here byte tx_buffer[noparse][[/noparse]256] ' <----------- Change Buffer Size Here PUB start(rxpin, txpin, mode, baudrate) : okay '(31, 30, 0, 9600) '' Start serial driver - starts a cog '' returns false if no cog available '' '' mode bit 0 = invert rx '' mode bit 1 = invert tx '' mode bit 2 = open-drain/source tx '' mode bit 3 = ignore tx echo on rx stop ' stop stops any existing running serial driver if say you reinitialized ' your program without previously stopping it. longfill(@rx_head, 0, 4) ' The longfill initializes the first 4 longs to zero ' (rx_head through tx_tail) longmove(@rx_pin, @rxpin, 3) ' The longmove copies the 4 parameters to start to the next 4 longs in ' the table (rx_pin through bit_ticks) bit_ticks := clkfreq / baudrate ' The assignment to bit_ticks computes the number of clock ticks for ' the Baud requested. buffer_ptr := @rx_buffer ' The assignment to buffer_ptr passes the address ' of the receive buffer (and the transmit buffer XX bytes further). okay := cog := cognew(@entry, @rx_head) + 1 ' The cognew starts the assembly driver and passes to it the starting ' address of this whole table which it uses to refer to the various ' items in the table (rx_head through buffer_ptr). PUB stop '' Stop serial driver - frees a cog if cog cogstop(cog~ - 1) longfill(@rx_head, 0, 9) PUB rxflush '' Flush receive buffer repeat while rxcheck => 0 PUB rxcheck : rxbyte '' Check if byte received (never waits) '' returns -1 if no byte received, $00..$FF if byte rxbyte-- if rx_tail <> rx_head rxbyte := rx_buffer[noparse][[/noparse]rx_tail] rx_tail := (rx_tail + 1) & $FF ' <----------- Change Buffer Size Here PUB rxtime(ms) : rxbyte | t '' Wait ms milliseconds for a byte to be received '' returns -1 if no byte received, $00..$FF if byte t := cnt repeat until (rxbyte := rxcheck) => 0 or (cnt - t) / (clkfreq / 1000) > ms PUB rx : rxbyte '' Receive byte (may wait for byte) '' returns $00..$FF repeat while (rxbyte := rxcheck) < 0 PUB tx(txbyte) '' Send byte (may wait for room in buffer) repeat until (tx_tail <> (tx_head + 1) & $FF) ' <----------- Change Buffer Size Here tx_buffer[noparse][[/noparse]tx_head] := txbyte tx_head := (tx_head + 1) & $FF ' <----------- Change Buffer Size Here if rxtx_mode & %1000 rx PUB str(stringptr) '' Send string repeat strsize(stringptr) tx(byte[noparse][[/noparse]stringptr++]) PUB dec(value) | i '' Print a decimal number if value < 0 -value tx("-") i := 1_000_000_000 repeat 10 if value => i tx(value / i + "0") value //= i result~~ elseif result or i == 1 tx("0") i /= 10 PUB hex(value, digits) '' Print a hexadecimal number value <<= (8 - digits) << 2 repeat digits tx(lookupz((value <-= 4) & $F : "0".."9", "A".."F")) PUB bin(value, digits) '' Print a binary number value <<= 32 - digits repeat digits tx((value <-= 1) & 1 + "0") DAT '*********************************** '* Assembly language serial driver * '*********************************** org ' ' ' Entry ' entry mov t1,par 'get structure address add t1,#4 << 2 'skip past heads and tails rdlong t2,t1 'get rx_pin mov rxmask,#1 shl rxmask,t2 add t1,#4 'get tx_pin rdlong t2,t1 mov txmask,#1 shl txmask,t2 add t1,#4 'get rxtx_mode rdlong rxtxmode,t1 add t1,#4 'get bit_ticks rdlong bitticks,t1 add t1,#4 'get buffer_ptr rdlong rxbuff,t1 mov txbuff,rxbuff add txbuff,#255 ' <----------- Change Buffer Size Here add txbuff,#1 ' <----------- add 1 more for 256 test rxtxmode,#%100 wz 'init tx pin according to mode test rxtxmode,#%010 wc if_z_ne_c or outa,txmask if_z or dira,txmask mov txcode,#transmit 'initialize ping-pong multitasking ' ' ' Receive ' receive jmpret rxcode,txcode 'run a chunk of transmit code, then return test rxtxmode,#%001 wz 'wait for start bit on rx pin test rxmask,ina wc if_z_eq_c jmp #receive mov rxbits,#9 'ready to receive byte mov rxcnt,bitticks shr rxcnt,#1 add rxcnt,cnt :bit add rxcnt,bitticks 'ready next bit period :wait jmpret rxcode,txcode 'run a chuck of transmit code, then return mov t1,rxcnt 'check if bit receive period done sub t1,cnt cmps t1,#0 wc if_nc jmp #:wait test rxmask,ina wc 'receive bit on rx pin rcr rxdata,#1 djnz rxbits,#:bit shr rxdata,#32-9 'justify and trim received byte and rxdata,#$FF test rxtxmode,#%001 wz 'if rx inverted, invert byte if_nz xor rxdata,#$FF rdlong t2,par 'save received byte and inc head add t2,rxbuff wrbyte rxdata,t2 sub t2,rxbuff add t2,#1 and t2,#$FF ' <----------- Change Buffer Size Here wrlong t2,par jmp #receive 'byte done, receive next byte ' ' ' Transmit ' transmit jmpret txcode,rxcode 'run a chunk of receive code, then return mov t1,par 'check for head <> tail add t1,#2 << 2 rdlong t2,t1 add t1,#1 << 2 rdlong t3,t1 cmp t2,t3 wz if_z jmp #transmit add t3,txbuff 'get byte and inc tail rdbyte txdata,t3 sub t3,txbuff add t3,#1 and t3,#$FF ' <----------- Change Buffer Size Here wrlong t3,t1 or txdata,#$100 'ready byte to transmit shl txdata,#2 or txdata,#1 mov txbits,#11 mov txcnt,cnt :bit test rxtxmode,#%100 wz 'output bit on tx pin according to mode test rxtxmode,#%010 wc if_z_and_c xor txdata,#1 shr txdata,#1 wc if_z muxc outa,txmask if_nz muxnc dira,txmask add txcnt,bitticks 'ready next cnt :wait jmpret txcode,rxcode 'run a chunk of receive code, then return mov t1,txcnt 'check if bit transmit period done sub t1,cnt cmps t1,#0 wc if_nc jmp #:wait djnz txbits,#:bit 'another bit to transmit? jmp #transmit 'byte done, transmit next byte ' ' ' Uninitialized data ' t1 res 1 t2 res 1 t3 res 1 rxtxmode res 1 bitticks res 1 rxmask res 1 rxbuff res 1 rxdata res 1 rxbits res 1 rxcnt res 1 rxcode res 1 txmask res 1 txbuff res 1 txdata res 1 txbits res 1 txcnt res 1 txcode res 1