From: Paul Hänsch <paul@plutz.net>
Date: Sun, 10 Mar 2019 14:51:23 +0000 (+0100)
Subject: service for reading mpu6050 data
X-Git-Url: http://git.plutz.net/?p=rpi_small;a=commitdiff_plain;h=4e295b63c502ada8cf02b4269c69e5ea14d909d7

service for reading mpu6050 data
---

diff --git a/files_gyro/opt/gyro/mpu6050.sh b/files_gyro/opt/gyro/mpu6050.sh
new file mode 100755
index 0000000..7184bff
--- /dev/null
+++ b/files_gyro/opt/gyro/mpu6050.sh
@@ -0,0 +1,78 @@
+#!/bin/sh
+
+CR="$(printf \\r)"
+
+i2cset -y 1 0x68 0x1b 0x08  # Set gyroscope to +/- 500º/sec (1º/s = 65.5)
+i2cset -y 1 0x68 0x1c 0x08  # Set accelerometer to +/- 4g (1g = 8192)
+
+read METHOD LOCATION PROTOCOL
+while read name value; do
+  [ ! "${name%$CR}" ] && break
+done
+
+printf 'HTTP/1.1 200 OK\r\n'
+printf '%s: %s\r\n' \
+    Connection close \
+    Access-Control-Allow-Origin '*' \
+    Content-Type text/event-stream
+printf '\r\n'
+
+da=0 db=0 dc=0 dn=0 dm=50
+aa=0 ab=0 ac=0
+
+while sleep .1; do 
+  i2cdump -y 1 0x68 i || break
+done \
+| sed -uEn '
+  # pick Hex values, pair them and generate decimal calculations
+  /^[3]0:/{
+    N;
+    s;^.{37}(.{15}).{24}(.{26}).{41}$; \1\2;;
+    s;(..) (..);\1\2;g;
+    s; (.)(.)(.)(.); 4096*\1+256*\2+16*\3+\4;g;
+    s;a;10;g; s;b;11;g; s;c;12;g; s;d;13;g; s;e;14;g; s;f;15;g;
+    p;}' \
+| while read x y z t a b c; do
+  # convert to decimal
+  x=$(($x)) y=$(($y)) z=$(($z)) t=$(($t)) a=$(($a)) b=$(($b)) c=$(($c))
+  # convert from unsigned to signed
+  x=$((x - (x/32768 * 65536))) y=$((y - (y/32768 * 65536))) z=$((z - (z/32768 * 65536)))
+  a=$((a - (a/32768 * 65536))) b=$((b - (b/32768 * 65536))) c=$((c - (c/32768 * 65536)))
+  t=$((t - (t/32768 * 65536)))
+
+  # measure gyroscope drift
+  if [ $dn -lt $dm ]; then
+    dn=$((dn + 1))
+    da=$((da + a)) db=$((db + b)) dc=$((dc + c))
+  elif [ $dn -eq $dm ]; then
+    dn=$((dn + 1))
+    da=$((da / dm)) db=$((db / dm )) dc=$((dc / dm))
+    aa=0 ab=0 ac=0
+  fi
+
+  # scale to proper range
+  x=$((x * 9810 / 8192)) y=$((y * 9810 / 8192)) z=$((z * 9810 / 8192))
+  a=$(((a - da) * 125000 / 8192)) b=$(((b - db) * 125000 / 8192)) c=$(((c - dc) * 125000 / 8192))
+  t=$((t * 1000 / 256))
+
+  # derive bearing from rotation
+  aa=$((aa + a / 10)) ab=$((ab + b / 10)) ac=$((ac + c / 10))
+
+  printf 'event: motion
+          data: %04i %04i %04i
+          
+          event: rotation
+          data: %04i %04i %04i
+
+          event: bearing
+          data: %04i %04i %04i
+          
+          event: temperature
+          data: %04i
+       \n' $x $y $z \
+	   $a $b $c \
+	   $((aa * 12500 / 8192)) $((ab * 12500 / 8192)) $((ac * 12500 / 8192)) \
+	   $t \
+  || break
+done \
+| sed -uE 's;^ +;;; s;[0-9]{3} ;.&;g; s;[0-9]{3}$;.&;; s;-\.;-0.;g;'
diff --git a/gyro.mk b/gyro.mk
index 268cc87..bc480e0 100644
--- a/gyro.mk
+++ b/gyro.mk
@@ -1,6 +1,9 @@
-PACKAGES := ${PACKAGES} i2c-tools
+PACKAGES := ${PACKAGES} i2c-tools openbsd-inetd
 
 .PHONY: gyro
 ${IMGFILE}: gyro
-gyro: imgmount root_copy
+gyro: imgmount root_copy files_gyro/
+	cp -a files_gyro/. "$<"
 	printf 'i2c-dev\n' >>"$</etc/modules"
+	printf '127.0.0.1:314	stream	tcp	nowait	root  /opt/gyro/mpu6050.sh	mpu6050\n' >>"$</etc/inetd.conf"
+