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com.serial.spin
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com.serial.spin
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' Original Authors: Jeff Martin, Andy Lindsay, Chip Gracey
{{
This object implements core serial functionality.
# Usage
- Call Start, or StartRxTx, first.
- Be sure to set the Parallax Serial Terminal software to the baudrate specified in Start, and the proper COM port.
- At 80 MHz, this object properly receives/transmits at up to 250 Kbaud, or performs transmit-only at up to 1 Mbaud.
}}
CON
BUFFER_LENGTH = 32 ' Recommended as 64 or higher, but can be 2, 4, 8, 16, 32, 64, 128 or 256.
BUFFER_MASK = BUFFER_LENGTH - 1
VAR
long cog ' Cog flag/id
long rx_head ' 9 contiguous longs (must keep order)
long rx_tail
long tx_head
long tx_tail
long rx_pin
long tx_pin
long rxtx_mode
long bit_ticks
long buffer_ptr
byte rx_buffer[BUFFER_LENGTH] ' Receive and transmit buffers
byte tx_buffer[BUFFER_LENGTH]
PUB Start(baudrate) : okay
{{
Start communication with the Parallax Serial Terminal using the Propeller's programming connection.
Waits 1 second for connection, then clears screen.
Parameters:
baudrate - bits per second. Make sure it matches the Parallax Serial Terminal's
Baud Rate field.
Returns True (non-zero) if cog started, or False (0) if no cog is available.
}}
okay := StartRxTx(31, 30, 0, baudrate)
PUB StartRxTx(rxpin, txpin, mode, baudrate) : okay
{{
Start serial communication with designated pins, mode, and baud.
Parameters:
rxpin - input pin; receives signals from external device's TX pin.
txpin - output pin; sends signals to external device's RX pin.
mode - signaling mode (4-bit pattern).
bit 0 - inverts rx.
bit 1 - inverts tx.
bit 2 - open drain/source tx.
bit 3 - ignore tx echo on rx.
baudrate - bits per second.
Returns : True (non-zero) if cog started, or False (0) if no cog is available.
}}
Stop
longfill(@rx_head, 0, 4)
longmove(@rx_pin, @rxpin, 3)
bit_ticks := clkfreq / baudrate
buffer_ptr := @rx_buffer
okay := cog := cognew(@entry, @rx_head) + 1
PUB Stop
{{
Stop serial communication; frees a cog.
}}
if cog
cogstop(cog~ - 1)
longfill(@rx_head, 0, 9)
PUB Count
{{
Get count of characters in receive buffer.
Returns: number of characters waiting in receive buffer.
}}
result := rx_head - rx_tail
result -= BUFFER_LENGTH*(Count < 0)
PUB Flush
{{
Flush receive buffer.
}}
repeat while RxCheck => 0
PUB Char(ch)
{{
Send single-byte character. Waits for room in transmit buffer if necessary.
Parameter:
bytechr - character (ASCII byte value) to send.
}}
repeat until (tx_tail <> ((tx_head + 1) & BUFFER_MASK))
tx_buffer[tx_head] := ch
tx_head := (tx_head + 1) & BUFFER_MASK
if rxtx_mode & %1000
CharIn
PUB CharIn
{{
Receive single-byte character. Waits until character received.
Returns: $00..$FF
}}
repeat while (result := RxCheck) < 0
PUB RxCheck
{
Check if character received; return immediately.
Returns: -1 if no byte received, $00..$FF if character received.
}
result~~
if rx_tail <> rx_head
result := rx_buffer[rx_tail]
rx_tail := (rx_tail + 1) & BUFFER_MASK
PUB GetMailbox
return @rx_head
DAT
org
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,#BUFFER_LENGTH
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
idle jmpret rxcode,txcode 'run chunk of tx code, then return
test rxtxmode,#%001 wz 'wait for idle rx line
test rxmask,ina wc
if_z_ne_c jmp #idle
receive jmpret rxcode,txcode 'run chunk of tx 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
:start jmpret rxcode,txcode 'run chunk of tx code, then return
test rxtxmode,#%001 wz 'check start bit on rx pin
test rxmask,ina wc
if_z_eq_c jmp #receive
mov t1,rxcnt 'check if bit receive period done
sub t1,cnt
cmps t1,#0 wc
if_nc jmp #:start
:bit add rxcnt,bitticks 'ready next bit period
:wait jmpret rxcode,txcode 'run chunk of tx 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,#BUFFER_MASK
wrlong t2,par
jmp #idle 'byte done, receive next byte
transmit jmpret txcode,rxcode 'run chunk of rx 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,#BUFFER_MASK
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
test rxtxmode,#%010 wc 'according to mode
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 chunk of rx 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
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