The Smell of Molten Projects in the Morning

Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.

Tag: Improvements

Making the world a better place, one piece at a time

Raspberry Pi Streaming Radio Player: Room Customization
Sometimes you (well, I) want a bit of late-night music, which is now one button press away. However, I initially set things up so the Raspberry Pi’s startup code executed a Python script on a network share from the file server in the basement, which shuts down around midnight after the daily backup.

Keeping a local copy meant having to update that copy whenever I tweak the code, a nuisance not to be tolerated. This Bash (or whatever) code in /etc/rc.local figures out if the server is up and, if so, updates the local copy from the server. If the server isn’t up, then it just runs with what it has:
```
#!/bin/sh
# was !/bin/sh -e

... snippage ...

server=192.168.1.4

ping -c 1 $server
if [ $? -eq 0 ]
then
  mount -o ro ${server}:/mnt/bulkdata/Project\ Files/Streaming\ Media\ Player/Firmware/ /mnt/part
  rsync -auv /mnt/part/Streamer.py /home/pi
  umount /mnt/part
fi

sudo -u pi sh -c 'python /home/pi/Streamer.py any' &
```
N.B.: you must remove the -e from the shebang, because otherwise the script jams to a stop when the ping fails. Took me a while to figure that out, yup.

Use raspi-config to force the startup sequence to wait until the network is available. Turns out that the DHCP process can stall for half a minute, so fixed timeouts don’t work.

Hardcoding the server IP address eliminates a whole bunch of mysterious failures apparently due to whatever handles the translation from mollusk.local to the dotted quad. Maybe that’s not really a problem, but I’ll run with it.

Now the streamers fetch the Latest and Greatest version whenever they’re on during the day and run their local copy, with the room parameter telling it where it lives.

Life is good!
2017-01-17

Raspberry Pi Streaming Radio Player: Command Line Parsing

Some experience suggested different default stations & volume settings for the streamers in various rooms, so the Python code now parses its command line to determine how to configure itself:

import argparse as args

cmdline = args.ArgumentParser(description='Streaming Radio Player',epilog='KE4ZNU - http://softsolder.com')
cmdline.add_argument('Loc',help='Location: BR1 BR2 ...',default='any',nargs='?')
args = cmdline.parse_args()

I should definitely pick a different variable name to avoid the obvious clash.

With that in hand, the customization takes very effort:

CurrentKC = 'KEY_KP7'
MuteDelay = 8.5         # delay before non-music track; varies with buffering
UnMuteDelay = 7.5       # delay after non-music track
MixerVol = '15'         # mixer gain

Location = vars(args)['Loc'].upper()
print 'Player location: ',Location
logging.info('Player setup for: ' + Location)

if Location == 'BR1':
  CurrentKC = 'KEY_KPDOT'
  MixerVol = '10'
elif Location == 'BR2':
  MuteDelay = 6.0
  UnMuteDelay = 8.0
MixerVol = '5'

The Location = vars() idiom returns a dictionary of all the variables and their values, of which there’s only one at the moment. The rest of the line extracts the value and normalizes it to uppercase.

Now we can poke the button and get appropriate music without having to think very hard.

Life is good!

The Python source code, which remains in dire need of refactoring, as a GitHub Gist:

	from evdev import InputDevice,ecodes,KeyEvent
	import subprocess32 as subp
	import select
	import re
	import sys
	import time
	import logging
	import os.path
	import argparse as args

	cmdline = args.ArgumentParser(description='Streaming Radio Player',epilog='KE4ZNU – http://softsolder.com')
	cmdline.add_argument('Loc',help='Location: BR1 BR2 …',default='any',nargs='?')
	args = cmdline.parse_args()

	Media = {'KEY_KP7' : ['Classical',False,['mplayer','–quiet','-playlist','http://stream2137.init7.net/listen.pls'%5D%5D,
	'KEY_KP8' : ['Jazz',False,['mplayer','–quiet','-playlist','http://stream2138.init7.net/listen.pls'%5D%5D,
	'KEY_KP9' : ['WMHT',False,['mplayer','–quiet','http://wmht.streamguys1.com/wmht1'%5D%5D,
	'KEY_KP4' : ['Classic 1000',True,['mplayer','–quiet','-playlist','http://listen.radionomy.com/1000classicalhits.m3u'%5D%5D,
	'KEY_KP5' : ['DCNY 911',False,['mplayer','–quiet','-playlist','http://www.broadcastify.com/scripts/playlists/1/12305/-5857889408.m3u'%5D%5D,
	'KEY_KP6' : ['WAMC',False,['mplayer','–quiet','http://pubint.ic.llnwd.net/stream/pubint_wamc'%5D%5D,
	'KEY_KP1' : ['60s',True,['mplayer','–quiet','-playlist','http://listen.radionomy.com/all60sallthetime-keepfreemusiccom.m3u'%5D%5D,
	'KEY_KP2' : ['50-70s',True,['mplayer','–quiet','-playlist','http://listen.radionomy.com/golden-50-70s-hits.m3u'%5D%5D,
	'KEY_KP3' : ['Soft Rock',True,['mplayer','–quiet','-playlist','http://listen.radionomy.com/softrockradio.m3u'%5D%5D,
	'KEY_KP0' : ['Zen',True,['mplayer','–quiet','-playlist','http://listen.radionomy.com/zen-for-you.m3u'%5D%5D,
	'KEY_KPDOT' : ['Ambient',False,['mplayer','–quiet','http://185.32.125.42:7331/maschinengeist.org.mp3'%5D%5D
	}

	Controls = {'KEY_KPSLASH' : '//////',
	'KEY_KPASTERISK' : '******',
	'KEY_KPENTER' : ' ',
	'KEY_KPMINUS' : '<',
	'KEY_KPPLUS' : '>',
	'KEY_VOLUMEUP' : '*',
	'KEY_VOLUMEDOWN' : '/'
	}

	MuteStrings = ["TargetSpot","[Unknown]","Advert:","+++","—","SRR","Srr","ZEN FOR","Intro of","Jingle – ","bumper"]

	Muted = False # keep track of muted state

	MixerChannel = 'PCM' # which amixer thing to use

	logging.basicConfig(format='%(asctime)s %(levelname)s: %(message)s',filename='/tmp/Streamer.log',level=logging.INFO)
	logger = logging.getLogger()

	# Set up defaults based on where we are

	CurrentKC = 'KEY_KP7'
	MuteDelay = 8.5 # delay before non-music track; varies with buffering
	UnMuteDelay = 7.5 # delay after non-music track
	MixerVol = '15' # mixer gain

	Location = vars(args)['Loc'].upper()
	print 'Player location: ',Location
	logging.info('Player setup for: ' + Location)

	if Location == 'BR1':
	CurrentKC = 'KEY_KPDOT'
	MixerVol = '10'
	elif Location == 'BR2':
	MuteDelay = 6.0
	UnMuteDelay = 8.0
	MixerVol = '5'

	# set up event inputs and polling objects
	# This requires some udev magic to create the symlinks

	k = InputDevice('/dev/input/keypad')
	k.grab()

	kp = select.poll()
	kp.register(k.fileno(),select.POLLIN + select.POLLPRI + select.POLLERR)

	# if volume control knob exists, then set up its events

	VolumeDevice = '/dev/input/volume'

	vp = select.poll()
	if os.path.exists(VolumeDevice):
	v = InputDevice(VolumeDevice)
	v.grab()
	vp.register(v.fileno(),select.POLLIN + select.POLLPRI + select.POLLERR)

	# set up file for output tracing

	lw = open('/tmp/mp.log','w') # mplayer piped output

	# set the mixer output low enough that the initial stream won't wake the dead

	subp.call(['amixer','sset',MixerChannel,MixerVol])

	# Start the player with the default stream, set up for polling

	print 'Starting mplayer on',Media[CurrentKC][0],' -> ',Media[CurrentKC][-1][-1]
	logging.info('Starting mplayer on %s -> %s',Media[CurrentKC][0],Media[CurrentKC][-1][-1])
	p = subp.Popen(Media[CurrentKC][-1],
	stdin=subp.PIPE,stdout=subp.PIPE,stderr=subp.STDOUT)

	pp = select.poll() # this may be valid for other invocations, but is not pretty
	pp.register(p.stdout.fileno(),select.POLLIN + select.POLLPRI + select.POLLERR)

	print ' … running'

	#——————–
	#— Play the streams

	while True:

	# pluck next line from mplayer and decode it

	if [] != pp.poll(10):
	text = p.stdout.readline()

	if 'ICY Info: ' in text: # these lines may contain track names
	lw.write(text)
	lw.flush()

	trkinfo = text.split(';') # also splits at semicolon embedded in track name
	# logging.info('Raw split line: %s', trkinfo)
	for ln in trkinfo:
	if 'StreamTitle' in ln: # this part probably contains the track name
	NeedMute = False # assume a listenable track
	trkhit = re.search(r"StreamTitle='(.*)'",ln) # extract title if possible
	if trkhit: # regex returned valid result?
	TrackName = trkhit.group(1) # get string between two quotes
	else:
	print ' … regex failed for line: ', ln
	logging.info('Regex failed for line: [' + ln + ']')
	TrackName = "Invalid StreamTitle format"

	print 'Track name: [', TrackName, ']'
	logging.info('Track name: [%s]', TrackName)
	if Media[CurrentKC][1] and ( (len(TrackName) == 0) or any(m in TrackName for m in MuteStrings) ) :
	NeedMute = True

	if NeedMute:
	print ' … muting:',
	if Media[CurrentKC][1] and not Muted:
	time.sleep(MuteDelay) # brute-force assumption about buffer leadtime
	subp.call(['amixer','-q','sset',MixerChannel,'mute'])
	Muted = True
	print 'done'
	logging.info('Track muted')
	else:
	print ' … unmuting:',
	if Muted:
	if Media[CurrentKC][1]:
	time.sleep(UnMuteDelay) # another brute-force timing assumption
	Muted = False
	subp.call(['amixer','-q','sset',MixerChannel,'unmute'])
	print 'done'
	logging.info('Track unmuted')

	elif 'Exiting.' in text: # mplayer just imploded
	lw.write(text)
	lw.flush()
	print 'Got EOF / stream cutoff: []',text,']'
	logging.info('EOF or stream cutoff')
	print ' … killing dead mplayer'
	pp.unregister(p.stdout.fileno())
	p.terminate() # p.kill()
	p.wait()
	# print ' … flushing pipes'
	# lw.truncate(0)
	print ' … discarding keys'
	while [] != kp.poll(0):
	kev = k.read
	time.sleep(10)
	print ' … restarting mplayer: ',Media[CurrentKC][0]
	logging.info('Restarting mplayer')
	p = subp.Popen(Media[CurrentKC][-1],
	stdin=subp.PIPE,stdout=subp.PIPE,stderr=subp.STDOUT)
	pp.register(p.stdout.fileno(),select.POLLIN + select.POLLPRI + select.POLLERR)
	print ' … running'
	logging.info(' … running')


	# accept pending events from volume control knob

	if [] != vp.poll(10):
	vev = v.read()
	lw.write('Volume')
	lw.flush()
	for e in vev:
	if e.type == ecodes.EV_KEY:
	kc = KeyEvent(e).keycode

	# print 'Volume kc: ',kc

	if kc in Controls:
	print 'Vol Control: ',kc
	try:
	p.stdin.write(Controls[kc])
	except Exception as e:
	print "Can't send control: ",e
	print ' … restarting player: ',Media[CurrentKC][0]
	logging.info('Error sending volume, restarting player: ' + str(e))
	try:
	pp.unregister(p.stdout.fileno())
	except Exception as e:
	print 'Trouble unregistering stdout: ',e
	logging.info('Cannot unregister stdout: ' + str(e))
	time.sleep(2)
	p = subp.Popen(Media[CurrentKC][-1],
	stdin=subp.PIPE,stdout=subp.PIPE,stderr=subp.STDOUT)
	pp.register(p.stdout.fileno(),select.POLLIN + select.POLLPRI + select.POLLERR)
	print ' … running'
	logging.info(' … running')


	# accept pending events from keypad

	if [] != kp.poll(10):
	kev = k.read()
	lw.write("Keypad")
	lw.flush()
	for e in kev:
	if e.type == ecodes.EV_KEY:
	kc = KeyEvent(e).keycode

	if kc == 'KEY_NUMLOCK': # discard these, as we don't care
	continue

	# print 'Got: ',kc

	if (kc == 'KEY_BACKSPACE') and (KeyEvent(e).keystate == KeyEvent.key_hold):
	if True:
	print 'Backspace = shutdown!'
	p.kill()
	logging.shutdown()
	q = subp.call(['sudo','shutdown','-P','now'])
	q.wait()
	time.sleep(5)
	print "Oddly, we did not die…"
	else:
	print 'BS = bail from main!'
	logging.shutdown()
	sys.exit(0)
	break

	if KeyEvent(e).keystate != KeyEvent.key_down: # discard key up & other rubbish
	continue

	if kc in Controls:
	print 'Control:', kc
	logging.info('Control: ' + kc)

	try:
	p.stdin.write(Controls[kc])
	except Exception as e:
	print "Can't send control: ",e
	print ' … restarting player: ',Media[CurrentKC][0]
	logging.info('Error sending controls, restarting player: ' + str(e))
	try:
	pp.unregister(p.stdout.fileno())
	except Exception as e:
	print 'Trouble unregistering stdout: ',e
	logging.info('Cannot unregister stdout: ' + str(e))
	p.terminate() # p.kill()
	p.wait()
	time.sleep(2)
	p = subp.Popen(Media[CurrentKC][-1],
	stdin=subp.PIPE,stdout=subp.PIPE,stderr=subp.STDOUT)
	pp.register(p.stdout.fileno(),select.POLLIN + select.POLLPRI + select.POLLERR)
	print ' … running'
	logging.info(' … running')

	if kc in Media:
	print 'Switching stream to ',Media[kc][0],' -> ',Media[kc][-1][-1]
	logging.info('Switching stream: ' + Media[kc][0] + ' -> ' + Media[kc][-1][-1])
	CurrentKC = kc
	print ' … halting player'
	try:
	pp.unregister(p.stdout.fileno())
	except Exception as e:
	print 'Trouble unregistering stdout: ',e
	logging.info('Cannot unregister stdout: ' + str(e))
	try:
	p.communicate(input='q')
	except Exception as e:
	print 'Perhaps mplayer already died? ',e
	logging.info('Already died? ' + str(e))
	try:
	p.terminate() # p.kill()
	p.wait()
	except Exception as e:
	print 'Trouble with terminate or wait: ',e
	logging.info('Trouble with terminate or wait: ' + str(e))

	time.sleep(2)
	print ' … restarting player: ',Media[CurrentKC][0]
	p = subp.Popen(Media[CurrentKC][-1],
	stdin=subp.PIPE,stdout=subp.PIPE,stderr=subp.STDOUT)
	pp.register(p.stdout.fileno(),select.POLLIN + select.POLLPRI + select.POLLERR)
	print ' … running'
	logging.info(' … running')

	print 'Out of loop!'
	logging.shutdown()

view raw Streamer.py hosted with ❤ by GitHub

2017-01-16

Electronics vs. Dark Rooms

Despite its diminutive size, the white LED on the end of the Dell AC511 USB SoundBar lights up a dark bedroom surprisingly well:

Dell AC511 USB SoundBar – white power LED

That’s pretty much the only power-on indicator for the streaming players, so I didn’t want to just slap a strip of black tape over it. Instead, because white LEDs don’t emit much energy toward the red end of the spectrum, I made a cute little filter from a snippet of Primary Red gel filter material, surrounded by a black Gorilla Tape donut:

Red filter for Dell AC511 USB power LED

Two layers of Primary Red cut the light intensity to a dim glow that’s barely visible in daylight and completely inoffensive at night:

Red filter for Dell AC511 – installed

The blue activity LED on the SunFounder got the black electrical tape treatment, however, with just a sliver showing through to give a hint that it’s still active:

SunFounder RT5370 USB WiFi Adapter – masked LED

One of the other WiFi adapters has a pinhole over a red LED that’s barely visible. Another, seemingly identical one, lacks the red LED under the pinhole; when I asked the vendor about that, I was told it was removed “to save power.” Yeah, right. That was part of the motivation to try a different adapter next time around, with good results.

Of course, you must wrap an opaque black case around the Raspberry Pi to tamp down the red and green LEDs on the PCB. It’s possible to control them in software, with varying degrees of difficulty depending on which Pi you have, but …

2017-01-12
Raspberry Pi WiFi Adapters

One might be forgiven for thinking these two USB Wifi adapters are essentially identical:

USB Wifi adapters

Turns out the SunFounder RT5370 (on the top, with the stylin’ curved case) has better performance than the Wifi With Antenna (on the bottom, with full-frontal chunk goin’ on), by a not inconsiderable 5 to 10 dB. Boosting the received power level in the fringe areas of our house from -70 dBm to -63 dBm makes all the difference between not working and steady streaming.

The built-in WiFi antenna on a Raspberry Pi 3 ticks along 10 dB lower, with -80 dBm (10 pW!) at the receiver making for poor communication: a Pi 3 works perfectly within reasonable line-of-sight of the router (even through our wood floor) and wakes up blind in fringe areas. Hacking an external antenna probably helps, but definitely isn’t a net win compared to ten bucks worth of USB adapter.

The wavemon utility (it’s in the Raspbian repo) comes in handy for figuring that sort of thing.

There is, of course, no way to determine anything important about the adapters from their product descriptions, which are essentially identical, right down to the price. Neither have any product identification on their cases. The back of the package for the SunFounder gadget gives some specs, none of which may mean anything (clicky for more dots):

SunFounder RT5370 USB WiFi Adapter Specs

I ordered another SunFounder adapter, Just In Case it comes in handy, with the hope that both behave the same way.

2017-01-11
Raspberry Pi 3 Reset Switch

The (relatively) new Raspberry Pi 3 PCB layout puts the Run header in a different location than in the Pi 2, but a minute of filing gnaws a suitable opening:

Raspberry Pi 3 – Reset Switch

As before, a hot-melt glue blob holds the switch in place. I’d prefer a black case, if only to hide the blob, but clear-ish is what’s available right now.

Remember those orderly shutdowns, even at the cost of a keypad button!

2017-01-10
Cast Iron Pan Seasoning: Round 3

After seasoning the pan after every meal for a few weeks, then not doing that for a few more weeks, its thick glaze began looking somewhat scuffed:

Cast Iron Pan – scuffed

You may recognize some of those scars from the previous picture:

Wagner skillet – two weeks of use

Perhaps the multi-layer seasoning was entirely too thick and prone to chipping; this time, I’ll try a thinner coating. Because it’s cast iron, the pan under the coating remains undamaged.

A few hours in a bucket of sodium carbonate solution with a battery charger driving a few amps through it removed most of the glaze and a few minutes with a sponge sanding block cleaned off the rest. Applying flaxseed oil and heating it to 400 °F on a regular burner (under close supervision!) produced a nice coating:

Cast Iron Pan – seasoned

The single layer was way slick for veggies in the evening and handled the morning omelet with aplomb, so we’ll run with it until something interesting happens.

2017-01-08

Making and Mounting SD Card Backup Images

The process of creating, configuring, and backing up a Raspberry Pi goes a little something like this:

unzip /mnt/diskimages/ISOs/Raspberry\ Pi/2016-11-25-raspbian-jessie-lite.zip
sudo dcfldd statusinterval=16 bs=4M if=2016-11-25-raspbian-jessie-lite.img of=/dev/sdb
... Micro SD card to Pi, boot, perform various configuration tweaks ...
... card back to PC ...
sudo dcfldd statusinterval=16 bs=4M if=/dev/sdb of=Streamer5-2017-01-02.img
zip -1 Streamer5-2017-01-02.zip Streamer5-2017-01-02.img
rsync -ahuv --progress Streamer5-2017-01-02.zip /mnt/diskimages/ISOs/Raspberry\ Pi/

The ZIP operation crushes an 8 GB image down to 1.6 GB, obviously depending on most of the image being filled with binary zeros or foxes or something trivial like that. You could work around that with fsarchiver, at the cost of handling each partition separately.

You can pipe the incoming image through GZIP when you don’t need the image right away:

sudo dcfldd statusinterval=16 bs=4M if=/dev/sdb | gzip -1c > Streamer5-2017-01-02.gz

There’s an obvious gotcha when you try to write an image to a (slightly) smaller card than the one it came from. Writing a smaller image on a larger card works just fine.

With a raw image in hand, you must know the disk partition offsets within the image to mount them in loopback mode:

fdisk -l Streamer5-2017-01-02.img
Disk Streamer5-2017-01-02.img: 7.4 GiB, 7892631552 bytes, 15415296 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0xc280d360

Device                    Boot  Start      End  Sectors  Size Id Type
Streamer5-2017-01-02.img1        8192   137215   129024   63M  c W95 FAT32 (LBA)
Streamer5-2017-01-02.img2      137216 15415295 15278080  7.3G 83 Linux

Knowing the offsets, the mounts go like this:

sudo mount -o loop,offset=$(( 8192*512 )) Streamer5-2017-01-02.img /mnt/loop/
... snippage ...
sudo mount -o loop,offset=$(( 137216*512 )) Streamer5-2017-01-02.img /mnt/loop/

Because a Jessie Lite system will fit neatly into a 2 GB SD Card, you can trim the disk image to eliminate most of the unused space:

sudo losetup -f
/dev/loop0

sudo losetup /dev/loop0 Streamer5-2017-01-02.img

sudo partprobe /dev/loop0

sudo gparted /dev/loop0
... resize ext4 partition from 7 GB to 1.8 GB

sudo losetup -d /dev/loop0

fdisk -l Streamer5-2017-01-02.img
Disk Streamer5-2017-01-02.img: 7.4 GiB, 7892631552 bytes, 15415296 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0xc280d360

Device                    Boot  Start     End Sectors  Size Id Type
Streamer5-2017-01-02.img1        8192  137215  129024   63M  c W95 FAT32 (LBA)
Streamer5-2017-01-02.img2      137216 3833855 3696640  1.8G 83 Linux

truncate --size=$(( (3833855+1)*512 )) Streamer5-2017-01-02.img
... or, if you don't care about an exact fit, use ...
truncate --size=2G Streamer5-2017-01-02.img

The partition and filesystem will plump up to fill the SD Card during the first boot on the Raspberry Pi.

There exist automagic utilities for all that, but practicing simple stuff helps keep it all fresh…

2017-01-06

Tag: Improvements

Raspberry Pi Streaming Radio Player: Room Customization

Raspberry Pi Streaming Radio Player: Command Line Parsing

Electronics vs. Dark Rooms

Raspberry Pi WiFi Adapters

Raspberry Pi 3 Reset Switch

Cast Iron Pan Seasoning: Round 3

Making and Mounting SD Card Backup Images