Author: robhamerling
Date: Wed Oct 1 02:40:43 2008
New Revision: 340
Modified:
trunk/unvalidated/include/peripheral/usart/serial_hw_int_cts.jal
Log:
Added selective transmit buffer overflow action: discard or wait
Modified: trunk/unvalidated/include/peripheral/usart/serial_hw_int_cts.jal
==============================================================================
--- trunk/unvalidated/include/peripheral/usart/serial_hw_int_cts.jal
(original)
+++ trunk/unvalidated/include/peripheral/usart/serial_hw_int_cts.jal Wed
Oct 1 02:40:43 2008
@@ -19,9 +19,6 @@
--
-- Notes:
--
--- The RS232 interface chip may be any converter chip.
--- A MAX202 or similar with small or no external capacitors is preferred.
---
-- The PIC ports use positive logic:
-- '1' is positive voltage, '0' is ground.
--
@@ -32,53 +29,81 @@
-- 0 (zero) for start-, data- and stop-bits.
-- - Signal levels: 'mark' = -3V to -15V, 'space' = +3V to +15V
--
--- The MAX202 is not only a voltage level CONverter (between TTL and RS232)
--- but also a signal INverter. You should be aware of the following:
--- - The inversion of PIC data-in and data-out by the MAX202 is required
+-- Between PIC and RS232 normally an interface chip is used, such as a
+-- Maxim/Dallas MAX232 or MAX202. These are not only voltage level
CONverter
+-- but also signal INverter. You should be aware of the following:
+-- - The inversion of PIC data-in and data-out by the MAX2x2 is required
-- to convert data-, start- and stop-bits to/from the corresponding
-- RS232 polarity. So nothing special has to be done in the program
-- because the USART of the PIC uses 'inverted' signal levels!
--- - For CTS the inversion by the MAX202 is NOT desired.
+-- - For CTS the inversion by the MAX2x2 is NOT desired.
-- Therefore the program has to use inverted signalling for CTS:
--- 'FALSE' is used for ON and 'TRUE' for OFF!
+-- 'FALSE' is used for CTS ON and 'TRUE' for CTS OFF!
-- As a reminder for this 'inverted' logic the signal is called
--- serial_cts_inv (e.g. serial_CTS_inv = true means CTS is false!).
+-- serial_cts_inv (e.g. serial_CTS_inv = TRUE means CTS is FALSE!).
--
--- Remember also: RxD of RS232-plug connects to TX of PIC via MAX202
--- TxD of RS232-plug connects to RX of PIC via MAX202
+-- Remember also: RxD of RS232-plug connects to TX of PIC via MAX2x2
+-- TxD of RS232-plug connects to RX of PIC via MAX2x2
--
--- Available procedure/function for application programs:
+-- This library supports:
+-- - Data format: 8 bits data, 1 start-bit, 1 stop bit
+-- - Fixed speed in the range 1200..57600, depending on the resonator
+-- frequency (see BAUD RATES tables in the datasheet with BRGH=1).
+--
+-- Available procedures/functions for application programs:
+--
+-- - serial_setup() -- initialise
communications
+-- -- (called automatically)
+-- - serial_send_byte(byte out <byte>) -- send byte
+-- -- returns the transmitted
byte
+-- - serial_receive_byte(byte in <byte>) returns bit -- receive byte
+-- -- returns TRUE with data,
+-- -- FALSE when no data
available
--
--- - serial_setup()
--- - serial_send_byte(byte out <byte>)
--- - serial_receive_byte(byte in <byte>) returns bit
+-- =======================================================================
--
+-- Application program must specify _before_ including this library
+-- (values are recommended, if possible keep SERIAL_DELTA = 17).
--
--- =======================================================================
-
--- Application program must specify _before_ including this library:
-
-- const SERIAL_XMTBUFSIZE = 32 -- size of transmit buffer
-- const SERIAL_RCVBUFSIZE = 64 -- size of receive buffer
--- const SERIAL_DELTA = 17 -- spare receive buffer
space
+-- const SERIAL_DELTA = 17 -- spare space receive
buffer
--
--- const SERIAL_BPSRATE = 9600 -- host communications
+-- const SERIAL_BPSRATE = 19200 -- host communications
-- -- (range 9600..57600)
--
--- var bit serial_ctsinv is pin_B4 -- incoming flow ctl
+-- var bit serial_overflow_discard = [ FALSE | TRUE ]
+-- With transmit buffer
overflow:
+-- - TRUE: discard data
+-- - FALSE: wait for free
space
+-- With receive buffer
overflow
+-- data is always discarded
+-- without notification!
+--
+--
+-- var bit serial_ctsinv is pin_B4 -- incoming data flow
control
-- var bit serial_ctsinv_direction is pin_B4_direction
-
--- Notes: - The pins above are given as example for a 16F88.
--- - The pins for data transmit and receive are selected
automatically.
-
+--
+-- Notes: - For data transmit and receive the pins TX and RX are used
+-- automatically, these have not to be assigned by the
application.
+-- - The CTS pin selected above is an example!
+-- - When CTS flow control is not desired then assign both
+-- serial_ctsinv and serial_cts_inv_direction to a dummy bit,
+-- for example:
+-- var bit dummy_bit
+-- var bit serial_ctsinv is dummy_bit1
+-- var bit serial_ctsinv_direction is dummy_bit2
+-- - The serial_overflow_discard bit may be dynamically changed
+-- (depending on how important the data is for th receiving
party).
+--
-- =======================================================================
-
--- Circular buffers for communications with PC via UART:
+--
+-- Declare circular buffers for communications via UART:
var byte _serial_xmtbuf[SERIAL_XMTBUFSIZE] -- circular output buffer
var byte _serial_rcvbuf[SERIAL_RCVBUFSIZE] -- circular input buffer
--- Offsets in circular buffers:
+-- Declare offsets in circular buffers:
var byte _serial_offsetxmthead -- offset next byte from
appl
var byte _serial_offsetxmttail -- offset next byte to
port
@@ -157,6 +182,7 @@
serial_ctsinv = TRUE -- set CTS FALSE
end if
end if
+
end if
end if
@@ -213,18 +239,20 @@
--
-- input: byte to transmit
--
--- returns: transmitted byte
+-- returns: transmitted byte (or 0x00 when data discarded)
--
--- notes: - Initiates transmission (interrupt handler)
--- when not currently transmitting
--- - spin when transmit buffer full
--- (wait for free buffer space)
+-- notes: - Activates transmit interrupt handler when data buffered
+-- - When buffer full act as indicated in 'serial_overflow_discard'
+-- * TRUE: discard data
+-- (and return 0x00 as data byte)
+-- * FALSE: wait for free buffer space
+-- (returns only after data has been stored in buffer)
--
-- -----------------------------------------------
function serial_send_byte(byte in data) return byte is
- var byte new_serial_offset -- offset in circular
buffer
+ var byte newxmthead -- offset in circular
buffer
if (_serial_offsetxmthead == _serial_offsetxmttail & -- nothing
buffered
PIR1_TXIF == true) then -- and UART not busy
@@ -232,15 +260,23 @@
TXREG = data -- transmit byte
immediately
else -- use circular buffer
_serial_xmtbuf[_serial_offsetxmthead] = data -- put byte in buffer
- new_serial_offset = _serial_offsetxmthead + 1 -- offset next char
- if (new_serial_offset >= SERIAL_XMTBUFSIZE) then -- beyond buffer
boundary
- new_serial_offset = 0 -- wrap to begin
- end if
- while (new_serial_offset == _serial_offsetxmttail) loop -- buffer
full!
- -- nothing -- spin until something
xmit'd
- end loop
+ newxmthead = _serial_offsetxmthead + 1 -- offset next char
+ if (newxmthead >= SERIAL_XMTBUFSIZE) then -- beyond buffer end
+ newxmthead = 0 -- wrap to begin
+ end if
+ if (newxmthead != _serial_offsetxmttail) then -- buffer not full
+ _serial_offsetxmthead = newxmthead -- update offset
+ else -- buffer full!
+ if (serial_overflow_discard == FALSE) then -- do not discard
data!
+ while (newxmthead == _serial_offsetxmttail) loop -- buffer
full
+ -- nothing -- spin until something
xmit'd
+ end loop
+ _serial_offsetxmthead = newxmthead -- update offset
+ else
+ data = 0x00 -- indicate byte discarded
+ end if
+ end if
PIE1_TXIE = TRUE -- (re-)enable xmit
interrupts
- _serial_offsetxmthead = new_serial_offset -- update offset now
end if
return data -- transmitted byte!
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