February 2015 – Janoš Šikloši

http://www.dx.com/p/hdmi-to-av-cvbs-l-r-video-converter-black-287673?r=89918554

I just got HDMI2AV converter from DX. I was annoyed buy noise coming from power supply on analog audio output from Raspberry Pi and decided to buy this little adapter and see what will happen. I’m more than pleased with result. My Raspberry Pi is now connected via HDMI cable to HDMI2AV adapter, analog video from this adapter is connected to my CRT TV 🙁 and analog audio to Sony STR-485DE amplifier. I even think that video quality is a bit better. Analog video out from RPi looks washed out compared to output from HDMI2AV adapter. Overall I’m quite pleased with this adapter and how well it performs. Only problem that I encountered is that at first it didn’t work. I thought that device is faulty but when I connected it to STB it worked. I than tried playing with RPi config settings and found that there is config_hdmi_boost setting that accepts values from 0-7. I tried with 5 and it worked. Beside that I added hdmi_group=1 and hdmi_mode=17 (576p 50 Hz). I tried other resolutions and it looks same but I’m guessing that 576p is more CPU/GPU friendly than 1080p and my PAL CRT TV is 768×576 or less.

While ago I found project that emulates candle flame using attiny13 MCU and two colored LED (red/yellow) or alternately two separate LED’s. Project author used method of randomly turning on and off LED’s and it looked relatively OK but it was a bit hard for eyes. I decided to make it from scratch using PWM (Pulse wide modulation) that randomly changes light intensity instead of turning on and off completely LED’s. It resulted in much more realistic candle flame simulation. It’s handy for making romantic atmosphere without fear of setting fire 😉

Schematic

LED’s are connected through 100Ω resistor to PB0 and PB1 attiny13 pins (pin 5 and 6). Attiny is powered from 5V source. Program is written in Bascom. One thing that should be done while programming attiny is to change lfuse from 6A to 7A so that MCU clock is changed from default 1.2MHz to 9.6MHz and that also changes PWM speed so there is no visible blinking of LED’s due to low PWM frequency.

$regfile = "attiny13.dat"
$crystal = 9600000

$hwstack = 32
$swstack = 16
$framesize = 8
Config Watchdog = 256
Start Watchdog

     Tccr0a = &B10100001
     Tccr0b = &B00000011
     Config Pinb.0 = Output
     Config Pinb.1 = Output
     Do
       Reset Watchdog
       Pwm0a = Rnd(255)
       Pwm0b = Rnd(255)
       Waitms 100
     Loop

$regfile = "attiny13.dat"

$crystal = 9600000

$hwstack = 32

$swstack = 16

$framesize = 8

Config Watchdog = 256

Start Watchdog

Tccr0a = &B10100001

Tccr0b = &B00000011

Config Pinb.0 = Output

Config Pinb.1 = Output

Reset Watchdog

Pwm0a = Rnd(255)

Pwm0b = Rnd(255)

Waitms 100

Loop

And here is source and compiled hex file for download

pwmsveca.bas
pwmsveca.hex

Month: February 2015

Raspbery Pi and HDMI2AV

Attiny13 PWM Candle