Version 3 of Uli Ender bitbang I2C with Arduino
Updated 2019-11-23 19:03:04 by JorgeJM 23 Nov 2019 - Uli Ender presented "Using Tcl for simple hardware-interfaces" back in 2014 (EuroTcl)
The key element from his presentation was to hack commonly available PC accessories in such a way that they can be converted into I/O interfaces for electronic projects (this look very valuable as a tool to be used to teach electronics)
Nowadays the Arduino is commonly available and relatively low-cost, so I made this minor adaptation to use Ender's code to use Arduino instead of the proposed hack to a mouse he presented back then.
What you need:
- Arduino UNO or similar (loaded with Standard Firmata)
- PC with a Tcl interpreter (preferable undroidwish, which already includes the tfirmata library)
- The LCD with I2C "backpack" module
This code is not yet processing the data from the slave, i.e:
- ACK is being ignored in this demo
- you cannot use it (yet) to read an I2C temperature sensor for example, as you can only write at this point
From the 13 digital pins on Arduino UNO, I used (hard coded):
digital pin 2 for SCL
digital pin 3 for SDA
Also, the Arduino is powering the LCD modules with +5V and GND
See Also: Example #2 from the Firmata page in this wiki
The LCD with I2C "backpack" module is pre-wired like this:
+
1 2 3 |
+ + + |
| | | +-------+-------+
| | | | 2 |
+-+---+--+---+ | |
16| A0 A1 A2 | | |
+-------+V P0+--------+4 RS 3+-----+
| | | |
| P1+--------+5 RW |
15| | | |
+------+SDA P2+--------+6 EN |
| | | |
| PCF8574 P3| | LCD |
14| | | |
+------+SCL | DB4| |
| P4+--------+11 |
| | DB5| |
13| P5+--------+12 |
+------+INT | DB6| |
| P6+--------+13 |
| | DB7| |
| P7+--------+14 |
| | DB3| |
| 8 | +--+10 |
+--+---------+ DB2| |
| +--+9 |
v DB1| |
+--+8 |
DB0| |
+--+7 1 |
+-------+-------+
|
v
and the Tcl code:
package require tfirmata
set bd [tfirmata::open COM4]
### i2C.demo 1
global rechteck rechteck2 iks scl sda sda2 abstand dauer ser
set scl 180
set sda 30
set sda2 30
set abstand 4
set dauer 100
proc init {} {
global rechteck rechteck2 iks scl sda abstand dauer
set iks 80
destroy .i2c
toplevel .i2c
wm geometry .i2c 1020x510+0+0
# wm geometry .i2c 785x380+0+0
destroy .i2c.c1
canvas .i2c.c1
pack .i2c.c1 -expand yes -fill both
### scl H
if {$scl == 180} {set rechteck [.i2c.c1 create rectangle 0 190 50 380 -fill black]}
### scl L
if {$scl == 250} {set rechteck [.i2c.c1 create rectangle 0 190 50 380 -fill white]}
### sda H
if {$sda == 30} {set rechteck2 [.i2c.c1 create rectangle 0 0 50 188 -fill black]}
if {$sda == 100} {set rechteck2 [.i2c.c1 create rectangle 0 0 50 180 -fill white]}
if 0 {
button .i2c.c1.b2 -text "a
u
t
o"
button .i2c.c1.b3 -text "s
t
e
p"
place .i2c.c1.b2 -x 735 -y 0 -height 190 -width 52
place .i2c.c1.b3 -x 735 -y 190 -height 190 -width 52
}
.i2c.c1 create text 65 30 -text H
.i2c.c1 create text 65 100 -text L
.i2c.c1 create text 65 180 -text H
.i2c.c1 create text 65 250 -text L
.i2c.c1 create text 80 120 -text SDA
.i2c.c1 create text 80 270 -text SCL
bind .i2c.c1 <ButtonPress-3> {
global sda2 rechteck2
set sda2 100
.i2c.c1 itemconfigure $rechteck2 -fill blue
update
}
bind .i2c.c1 <ButtonRelease-3> {
global sda2 rechteck2
set sda2 30
.i2c.c1 itemconfigure $rechteck2 -fill yellow
update
}
seitwaerts
seitwaerts
seitwaerts
seitwaerts
}
proc seitwaerts {} {
global iks sda scl abstand dauer
set iks2 $iks
incr iks $abstand
.i2c.c1 create line $iks2 $sda $iks $sda
.i2c.c1 create line $iks2 $scl $iks $scl
after $dauer
update
}
###################################################################
proc sdaH {} {
global bd
global iks sda rechteck2 ser
.i2c.c1 itemconfigure $rechteck2 -fill black
$bd mode 3 in
$bd dset 3 1
}
proc sdaHH {} {
global iks sda
.i2c.c1 create line $iks $sda $iks 30
set sda 30
}
proc sdaL {} {
global bd
global iks sda rechteck2 ser
.i2c.c1 create line $iks $sda $iks 100
set sda 100
.i2c.c1 itemconfigure $rechteck2 -fill white
$bd mode 3 out
$bd dset 3 0
}
proc sclH {} {
global bd
global iks scl rechteck ser
.i2c.c1 create line $iks $scl $iks 180
set scl 180
.i2c.c1 itemconfigure $rechteck -fill black
$bd mode 2 in
$bd dset 2 1
}
proc sclL {} {
global bd
global iks scl rechteck ser
.i2c.c1 create line $iks $scl $iks 250
set scl 250
.i2c.c1 itemconfigure $rechteck -fill white
$bd mode 2 out
$bd dset 2 0
update
}
###################################################################
proc start {} {
global iks
.i2c.c1 create text $iks 315 -anchor nw -text " Start"
seitwaerts
sdaL
.i2c.c1 create text $iks 130 -text S
seitwaerts
}
proc stop {} {
global iks
.i2c.c1 create text $iks 315 -anchor nw -text " Stop"
s 0
seitwaerts
seitwaerts
seitwaerts
seitwaerts
sdaH
sdaHH
.i2c.c1 create text $iks 130 -text P
seitwaerts
seitwaerts
seitwaerts
seitwaerts
}
proc s {w} {
global iks sda2 x ser
seitwaerts
sclL
seitwaerts
if {$w == "1" || $w == "A"} { sdaH }
#after 100
tfirmata::sleep 100
update
if {$w == "A" && $sda2 == 30} {set w "N"}
if {$w == "1" && $sda2 == 100} {set w "0"}
if {$w == "0" || $w == "a" || $w == "A"} { sdaL }
if {$w == "1" || $w == "N"} { sdaHH }
seitwaerts
sclH
.i2c.c1 create text $iks 130 -text $w
seitwaerts
}
proc adresse {a} {
set b [format %c $a]
binary scan $b B8 var
set n 0
while {$n < 8} {
set bit [string index $var $n]
if {$bit == 0} { s 0 }
if {$bit == 1} { s 1 }
incr n
}
}
proc chipadresse {a} {
global iks
.i2c.c1 create text $iks 300 -anchor nw -text " sende Chipadresse $a"
adresse $a
s A
}
proc sende {a} {
global iks
.i2c.c1 create text $iks 300 -anchor nw -text " sende $a"
adresse $a
s A
}
init
stop
proc enviar {addr args} {
start
chipadresse 78
foreach byte $args {
sende $byte
puts ">>> $byte"
}
stop
}
proc sendData {byte} {
set byte [string range $byte end-1 end]
puts "byte: $byte"
foreach {n1 n2} [split $byte ""] break
scan ${n1}5 %x part1
scan ${n1}1 %x part2
scan ${n2}5 %x part3
scan ${n2}1 %x part4
enviar 78 $part1 $part2 $part3 $part4
}
enviar 78 52 48
enviar 78 52 48 52 48 36 32 36 32
enviar 78 196 192
enviar 78 4 0 20 16
enviar 78 4 0 196 192
enviar 78 4 0 100 96
# enviar 78 69 65 21 17
foreach letter [split "Tcl/Tk & Arduino" ""] {
puts "Sending letter: $letter ==="
binary scan $letter H2 valor
sendData $valor
}
if 0 {
start
chipadresse 78
sende 4
sende 0
sende 20
sende 16
stop
start
chipadresse 78
sende 69
sende 65
sende 21
sende 17
stop
}
$bd close