Serial output
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Does anyone know if it's possible to send a serial string of 5 bytes
with 1 startbit, 8 databits, 1 even paritybit and 1 stopbit with the
BS2 ? The bitrate should be 2400 bps.
Is it possible to get 2400 bps by using the low, high or toggle
commands and send it bit by bit - or do you have any other
suggestion ?
(The SEROUT command does not support 8 databits + parity bit !!)
with 1 startbit, 8 databits, 1 even paritybit and 1 stopbit with the
BS2 ? The bitrate should be 2400 bps.
Is it possible to get 2400 bps by using the low, high or toggle
commands and send it bit by bit - or do you have any other
suggestion ?
(The SEROUT command does not support 8 databits + parity bit !!)
Comments
>with 1 startbit, 8 databits, 1 even paritybit and 1 stopbit with the
>BS2 ? The bitrate should be 2400 bps.
>Is it possible to get 2400 bps by using the low, high or toggle
>commands and send it bit by bit - or do you have any other
>suggestion ?
>
>(The SEROUT command does not support 8 databits + parity bit !!)
Each bit at 2400 baud is 417 microseconds. You might be able to send
each byte with a subroutine such as the following. You have to enter
the subroutine with the word variable serword already loaded with the
11 bits that need to be transmitted, including the start bit, 8 data
bits, parity bit (your program has to calculate parity), and the stop
bit.
' word variable serit contains the assembled 11 bits
' right justified
' adjust the variable "padding" to get correct timing
' p1 is a dummy pulse that appears, just for timing.
' the out command takes about 220 microseconds,
' the pulsout takes another 220 microseconds, plus
' the length of the dummy pulse.
Send_2400:
output 0
out0=serword.bit10 ' start bit
pulsout 1,padding
out0=serword.bit9
pulsout 1,padding
out0=serword.bit8
pulsout 1,padding
out0=serword.bit7
pulsout 1,padding
out0=serword.bit6
pulsout 1,padding
out0=serword.bit5
pulsout 1,padding
out0=serword.bit4
pulsout 1,padding
out0=serword.bit3
pulsout 1,padding
out0=serword.bit2
pulsout 1,padding
out0=serword.bit1
pulsout 1,padding
out0=serword.bit0 ' stop bit
RETURN
A FOR-NEXT loop probably would not work, because the FOR-NEXT logic
takes about 800 microseconds.
-- regards,
Tracy
>>with 1 startbit, 8 databits, 1 even paritybit and 1 stopbit with the
>>BS2 ? The bitrate should be 2400 bps.
>>Is it possible to get 2400 bps by using the low, high or toggle
>>commands and send it bit by bit - or do you have any other
>>suggestion ?
>>
>
> >(The SEROUT command does not support 8 databits + parity bit !!)
The question was how to transmit 8 bits, even parity, which is not
one of the built-in modes for SEROUT. In actually playing with this
a little more on a BS2, I found the following subroutine comes
pretty close to 2400 baud, 417 microseconds per bit, and calculates
the parity and sends out the data least significant bit first (rs232
standard), with a start bit and a stop bit.
'{$STAMP BS2}
'{$PBASIC 2.5}
' word variable wx contains the assembled 11 bits
' right justified, including 8 bits & parity
' the subroutine send2400 adjusts the timing
' using ~~~ operators.
wx VAR Word
wx0 VAR wx.BIT0 ' alias first bit for implied array
mybyte VAR byte ' byte to transmit
i VAR nib ' index
OUTPUT 2
DO
PULSOUT 1,10 ' 'scope trigger
mybyte=$55 ' example value
GOSUB send2400 ' send it over and over
LOOP
send2400:
wx=mybyte
FOR i=0 TO 7
wx.bit8= wx0(i) ^ wx.bit8 ' calculate even parity
NEXT
wx = wx << 1 | 1 ' append start bit on right
wx=wx ^ %11011011011 ' pre-compensate for inversions to follow
OUT2= ~~~wx0(0) ' start bit
OUT2= ~~~wx0(1) ' data bit 0
OUT2= ~~~~wx0(2) ' the ~~~~ or ~~~ pad the time per bit
OUT2= ~~~wx0(3)
OUT2= ~~~wx0(4)
OUT2= ~~~~wx0(5)
OUT2= ~~~wx0(6)
OUT2= ~~~wx0(7)
OUT2= ~~~~wx0(8) ' data bit 7
OUT2= ~~~wx0(9) ' even parity
OUT2= ~~~wx0(10) ' stop bit
RETURN
A suggestion I made in an earlier post, using PULSOUT to pad the
timing, simply takes too long on the BS2. It can't get down to 417
microseconds per bit. It would work for 1200 baud, though!
-- Tracy