we may be able to send from the CHIP

2 files changed, 71 insertions, 0 deletions

diff --git a/trasmitter/README.rst.txt b/trasmitter/README.rst.txt
index e231527..4b9e310 100644
--- a/trasmitter/README.rst.txt
+++ b/trasmitter/README.rst.txt
@@ -29,3 +29,12 @@ The two sequences are:
 
 Actually no, the pulses are not ½ high and ½ low, they're shaped
 weird. The source code has the correct widths.
+
+Without Arduino
+===============
+
+The GPIO / XIO pins on NextThing's CHIP, even when driven via the `slow
+sysfs interface`_, seem to be fast enough for our purposes.
+
+See the ``sender-chip.pl`` test program.
+
diff --git a/trasmitter/sender-chip.pl b/trasmitter/sender-chip.pl
new file mode 100644
index 0000000..27ae20e
--- /dev/null
+++ b/trasmitter/sender-chip.pl
@@ -0,0 +1,62 @@
+#!/usr/bin/env perl
+use strict;
+use warnings;
+use Time::HiRes qw(usleep sleep gettimeofday tv_interval);
+
+my $base = do {
+    open my $fh,'<','/sys/class/gpio/gpiochip405/base' or die "can't get base: $!";
+    my $line = <$fh>;
+    chomp($line);
+    $line;
+};
+
+sub gpio_enable {
+    my ($pin,$state) = @_;
+
+    if ($state) {
+        open my $fh,'>','/sys/class/gpio/export' or die "Can't export: $!";
+        print $fh $pin,"\n";
+    }
+    else {
+        open my $fh,'>','/sys/class/gpio/unexport' or die "Can't unexport: $!";
+        print $fh $pin,"\n";
+    }
+}
+
+sub gpio_direction {
+    my ($pin,$direction) = @_;
+
+    my $file = "/sys/class/gpio/gpio$pin/direction";
+    open my $fh,'>',$file
+        or die "Can't direction $file: $!";
+    print $fh ($direction ? 'out' : 'in' ),"\n";
+}
+
+sub gpio_write {
+    my ($pin,$value) = @_;
+
+    open my $fh,'>',"/sys/class/gpio/gpio$pin/value"
+        or die "Can't write: $!";
+    print $fh $value,"\n";
+}
+
+my $pin = 132; # CSID0
+#my $pin = $base+0; # XIO0
+
+gpio_enable($pin,1);
+gpio_direction($pin,1);
+gpio_write($pin,0);
+$SIG{INT} = sub {warn"disabling";gpio_enable($pin,0) };
+END { warn"disabling";gpio_enable($pin,0) }
+
+my $width = 400; # this seems to provide pulse widths close enough to
+                 # what we need, it's 106 samples at 192kHz
+while (1) {
+    for (0..50) {
+        gpio_write($pin,1);
+        usleep($width);
+        gpio_write($pin,0);
+        usleep($width);
+    }
+    sleep(0.5);
+}