Serial port buffering
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Posts: 46,084
I noticed Parallax has posted the draft of part II of my SX tutorial. The
unit at
http://www.sxtech.com/downloads/Unit%207%20-%20A%20Practical%20Design%20-%20
The%20SSIB.PDF
has the SSIB which is a dual channel serial buffer for the Stamp. It is
based on the SX. If you can't program an SX -- and Parallax agrees -- I
might be persuaded to make these available.
The idea behind the SSIB is that you have 2 serial input channels (TTL
level, true or inverted) at 9600 baud. Meanwhile the Stamp listens to the
SSIB at 19200 baud. There are two enable lines. When you assert enable "A",
you will read from channel A. When you assert enable "B" you read from
channel B. No assert, no data is sent to the Stamp. The SSIB buffers 16
characters on each channel. It also has an outbound handshake that can
signal the other device that its buffer is filling up (14 characters turns
it on by default).
This allows you to read 2 channels with 3 pins. For example:
serin 14\12, baudrate, [noparse][[/noparse]dec somenum]
serin 14\13, baudrate, [noparse][[/noparse]dec bnum]
The SSIB input is on pin 14. The A enable is on 12 and the B enable is on
13.
The SSIB chapter of the tutorial has sample Stamp code. If you can burn an
SX, you can change the baud rates, etc.
Regards,
Al Williams
AWC
*Floating point math for the Stamp, PIC, SX, or any microcontroller:
http://www.al-williams.com/awce/pak1.htm
P.S. The Stamp Project of the Month is late this month as you have likely
surmised. Its on its way very very soon!
unit at
http://www.sxtech.com/downloads/Unit%207%20-%20A%20Practical%20Design%20-%20
The%20SSIB.PDF
has the SSIB which is a dual channel serial buffer for the Stamp. It is
based on the SX. If you can't program an SX -- and Parallax agrees -- I
might be persuaded to make these available.
The idea behind the SSIB is that you have 2 serial input channels (TTL
level, true or inverted) at 9600 baud. Meanwhile the Stamp listens to the
SSIB at 19200 baud. There are two enable lines. When you assert enable "A",
you will read from channel A. When you assert enable "B" you read from
channel B. No assert, no data is sent to the Stamp. The SSIB buffers 16
characters on each channel. It also has an outbound handshake that can
signal the other device that its buffer is filling up (14 characters turns
it on by default).
This allows you to read 2 channels with 3 pins. For example:
serin 14\12, baudrate, [noparse][[/noparse]dec somenum]
serin 14\13, baudrate, [noparse][[/noparse]dec bnum]
The SSIB input is on pin 14. The A enable is on 12 and the B enable is on
13.
The SSIB chapter of the tutorial has sample Stamp code. If you can burn an
SX, you can change the baud rates, etc.
Regards,
Al Williams
AWC
*Floating point math for the Stamp, PIC, SX, or any microcontroller:
http://www.al-williams.com/awce/pak1.htm
P.S. The Stamp Project of the Month is late this month as you have likely
surmised. Its on its way very very soon!