Links to all my notes (includes mini-projects and source code etc)
(+) 0001 How do I change the Pi System partition size ?
(+) 0100 Device tree settings
(+) 0201 Power over Ethernet - (PoE)
(+) 0202 Solar Power - (with WiFi)
(+) 0203 Power Bank pass through
(+) 0400 Accessing the SDHC card system image
(+) 0401 Accessing PC shares from the Pi
(+) 0402 Installing samba - (the Pi as a Network Share on your PC)
(+) 0900 Can this approach be scaled up to a PC UPS ?
(+) 1001 Pandora Spotify on the Pi
(+) 1002 Playing movies on the Pi
(+) 1003 Getting VGA from the HDMI socket
(+) 1004 Using the RCA socket
(+) 1005 Using the Pi RS232 serial links
(+) 1006 Using the GPIO pins
(+) 1007 Controlling the Pi Zero ACT LED
(+) 1200 List of standard camera modes
(+) 1300 Auto file names
(+) 6500 How to make the System partition read only ?
(+) 6501 Minimising SDHC corruption on power down
(+) 9000 diode switch
(+) 9001 Auto shut down
(+) 9001 MOSFET switch
(+) C201 High speed photos
(+) Dec 1969 (no desc)
(+) a000 Display setup - (for PhotoFrame)
(+) a001 go photoframe - (how it works)
(-) a002 set photo - (select for display)
How the set-photo script works
All this script has to do is find the 'next' photo, copy it to the 'free' buffer and re-link display.jpg to the just 'filled' buffer (thus freeing the other buffer). Of course it's not quite that simple :-) To avoid any 'missing file' errors (and speed up the appearance of new photos), the /photos folder contents must be checked just before choosing the next photo - which is then immediately copied to ram-disk (to avoid it being deleted). Further, when choosing 'next' we have to cope with the current photo being deleted and also with new photos being added. Set up the /photos folder and the ram-disk (/photos/ram-disk) This script has to check for and set-up the /photos folder and files (because get-photo script is optonal and fbi has to be launched last)
#!/bin/bash
# set-photo.sh script for Mk2 PhotoFrame, last modified 28 Sept. 2016
# start by creating the required folders (don't matter if they already exist)
sudo mkdir /photos
sudo mkdir /photos/ram-disk
# check if we need to add ram-disk to the fstab file
mkram="tmpfs /photos/ram-disk tmpfs nodev,nosuid,size=5M 0 0"
# (5M bytes should be plenty)
if grep -Fxq "$mkram" /etc/fstab; then
echo "ram-disk found in fstab, going for mount"
else
sudo sh -c "echo \"$mkram\" >> /etc/fstab"
# alternate is: echo "$mkram" | sudo tee -a /etc/fstab > /dev/null
fi
# mount /photos/ram-disk to tmpfs
sudo mount -a
# show status (check if the /photos/ram-disk has 'mounted' to tmpfs) :-
df -HT
# create the buffer files (just in case we try to link before copying a photo)
touch /photos/ram-disk/buffer1.jpg
touch /photos/ram-disk/buffer2.jpg
touch /photos/ram-disk/display.jpg
Housekeeping done, now choose the next photo to be displayed. The directory listing is in 'date' order, so any newly created thumbnail(s) will be listed first. If the current top of list differs from previous, it's a new photo and it is chosen next. Otherwise we saerch for the current photo and choose the one after that - if the current is not found (or it's bottom of the listing) the top of the list if chosen. Finally, the new photo is to be copied to ram-disk/bufferX (and the free/busy buffers switched)
The /photos folder holds pre-sized .jpg's to be displayed, and the /photos/ram-disk (tmpfs) folder holds both 'buffers' (buffer1.jpg, buffer2.jpg) and the display.jpg 'virtual' file name (which will be 'linked' to one of the buffers)
The 3 'alias' files needed by fbi will be created (and linked actual to virtual, display.jpg to alias) by the fbi script.
One thing to watch out for is to avoid 'overwriting' the 'just free' buffer too quickly = it takes fbi 1 second to stop 'reading' the old buffer and follow the alias - display - new buffer link.
# check we have at least one photo
while ![ ls -U /photos/*.jpg 1> /dev/null 2>&1 ]; do
echo "waiting for jpgs in photos folder"
sleep 5
done
#
# OK, we have a photo, lets go
#
# Select and copy the next photo into the free buffer and then updates the display alias
# Source photos are held as thumbnails in the /photos/ folder (fetching and resizing is performed by the get-photo script)
# Both buffers1&2.jpg and display.jpg are held in the /ram-disk/ folder (the actual display is performed by the fbi script)
showtime=4 #photo show time -1 (so 4 = 5 seconds total)
cfile="0" # current file name
ctop="0" # current top by date
nbuf="buffer1.jpg" # next (free) buffer
# loop forever
while [ true ]; do
top="0" # no top found
next="0" # no next found
# Scan the photos dir for the current file
for filename in $(ls -A1c /photos/*.jpg); do
# note, when you ls a different folder, the path is added to each file name (so file is /photos/name.jpg )
if [ $top = "0" ]; then
top=$filename
if [ $filename != $ctop ]; then next=$filename; fi
fi
# find the next file AFTER the current
if [ $next = "0" ]; then
if [ $cfile = "0" ]; then next=$filename; fi
if [ $filename = $cfile ]; then cfile="0"; fi
fi
done
# if no next found, use top
if [ $next = "0" ]; then next=$top; fi
ctop=$top
# OK, we have the next file, pause in case fbi is still reading the free buffer
sleep 1
cp -f $next /photos/ram-disk/$nbuf
cfile=$next
if [ $nbuf = "buffer1" ] then;
nbuf="buffer2.jpg"
else
nbuf="buffer1.jpg"
fi
# now switch the link on first pass should creates display.jpg)
ln -s -f /photos/ram-disk/$nbuf /photos/ram-disk/display.jpg
# wait for the rest of the show time
sleep $showtime
# now go find the next
done
After creating the new script, don't forget to make it 'executable' :-
$ sudo chmod +x /photos/set-photo.sh
To test this from the command line (after you cd to /photos i.e. the directory where the script resides) just type :-
./set-photo.sh
This note last modified: 17th Nov 2017 17:29.