|
|
Emulator
7 segments displays driver
FORTH mini
system
Instructions
Use
Example
Principle
If the
7 segments displays of the
emulator are addressable registers in
the extension registers area of the FORTH core described as follows:
280
(0x118) display 0 (in left side)
281 (0x119) display 1
...
287 (0x11F) display 7 (in right side)
read/write:
bits[15..8] = 0x00
bits[7..0] = a,b,c,d,e,f,g,dp
lit segment if 1
The driver will allow to facilitate the use of these registers while
making
use of the real-time kernel. The principle consists in making i
possible the developer to have only to manage a simple 8 characters
string in ASCII coded.
For
the FORTH mini system emulator, the 8 7 segments displays are
wired on the components PCF8574 and PCF8574A of I2C port numeros 3 to 6.
The PCF8574 numero 3 is corresponding to
the first display and the PCF8574A numero 6 to the eighth display. The
electrical schematic is the following:
Instructions
- CW_AFFICHEUR 280
Numero of the first
extension register of the 8 7 segments displays.
This
instruction does not exist in the FORTH mini system,
The access to the displays is made with the instructions
I2C_PCF8574_C@, I2C_PCF8574_C!,
I2C_PCF8574A_C@
and I2C_PCF8574A_C! numeros 3 to 6.
adr_chr AFFICHEUR -
Displaying
of the 8 ASCII characters.
adr_chr is the address of the first of the 8 ASCII
coded characters (8 bits by character).
If the bit 7 of the character is set to "1", the
dot of the corresponding display is lit.
Use
The
driver not being integrated into the kernel, it is initially necessary
to compile the source file 7_segments.txt
before being able to use it.
For the FORTH mini
system, it is initialy necessary to compile first the I2C drivers
described in the source files pcf8574.txt
and pcf8574a.txt
then compile 7_segments.txt.
The
following sequence is corresponding to the displaying of "12345678":
" 12345678"
STRING S_NUMBER
S_NUMBER 1+ AFFICHEUR
The driver uses a table allowing to transform each of the 8 ASCII coded
to a displaying character (0 to 127). The bit 7 of each of the ASCII
coded allows to light the dot.
Example
The
following program installs a task which
display all the possible characters:
DECIMAL
"
" STRING S_AFFICHEUR (
8 spaces )
TACHE:
T_7_SEGMENTS
S_AFFICHEUR 1+ DUP AFFICHEUR DUP C@
IF
Left characters shifting )
DUP >R 1+ R@ 7 CMOVE R@ 8+ R@ DO
( Clearing of the last lit dot )
I C@ 127 AND I C!
LOOP
(Initialization of the dot with right shifting of the
precedent one )
R@ 7+ C@ DUP 127 = OVER 0= OR
IF
DUP XOR
ELSE
1+
THEN
( Progressive clearing of the string when the character 127
was displayed )
DUP R@ 7+ C! ?DUP
IF
7 AND R> + DUP >R C@ 128 OR
R> C!
ELSE
R> DROP
THEN
ELSE
( Initialization of the string and task removing )
8 32 FILL T_7_SEGMENTS T_RETIRE
THEN
;
500
T_7_SEGMENTS 32768 OVER T_AJOUTE T_PERIODE
Here is
a video:
|
|
 |
