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by hampi
Thu Nov 28, 2013 8:45 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: I2C clock stretching
Replies: 69
Views: 74316

Re: I2C clock stretching

Do NOT, EVERY try that with a PIC! There is an exception to this rule when you implement the i2c in software code. In my case I use the PIC interrupt INT to detect high to low transition which can be interpreted as a start bit if SCL stays high. My hacking can be seen from https://github.com/oh7bf/...
by hampi
Sun Nov 24, 2013 1:06 pm
Forum: General discussion
Topic: Request for ultra low power pi
Replies: 51
Views: 16040

Re: Request for ultra low power pi

I had the N1VG APRS weather station with a 7 Ah lead acid battery and 6 W solar panel running for two (or three?) years continuously until it stopped last June due to thunderstrom. Now I am putting my experience from that project to a solar powered computing project. See https://github.com/oh7bf/Ras...
by hampi
Sat Nov 23, 2013 4:11 pm
Forum: HATs and other add-ons
Topic: DIY PiSwitch - switching AC gracefully on and off
Replies: 17
Views: 20444

Re: DIY PiSwitch - switching AC gracefully on and off

Since the circuit has some similarity to what I am doing: I am switching the LM2576 regulator on/off with a transistor 2N3904. See the circuit diagram

https://github.com/oh7bf/RaspiPwr12V/bl ... pwr12V.pdf
by hampi
Sun Nov 03, 2013 3:07 pm
Forum: Automation, sensing and robotics
Topic: Power saving, using activity based power up/down
Replies: 6
Views: 1799

Re: Power saving, using activity based power up/down

I am using a PIC instead of 555 for similar task. The package is the same 8 pin DIP, but the PIC is more flexible though takes some time to program and debug. The basic circuit is in thread http://www.raspberrypi.org/phpBB3/viewtopic.php?f=41&t=59322 The push button could be replaced with some other...
by hampi
Tue Oct 29, 2013 7:09 pm
Forum: Other projects
Topic: DIY 12 V i2c controlled power supply
Replies: 2
Views: 2259

Re: DIY 12 V i2c controlled power supply

I have a similar cigarette lighter USB adapter for the 5 V. I have not tried to open it see what is inside. It might be possible to modify it to add a microcontroller inside to switch the power on/off. The main motivation for this project is the battery usage. When the Raspberry Pi is in halt mode a...
by hampi
Sun Oct 27, 2013 8:56 am
Forum: Other projects
Topic: DIY 12 V i2c controlled power supply
Replies: 2
Views: 2259

DIY 12 V i2c controlled power supply

If anybody is interested here is my power supply project https://github.com/oh7bf/RaspiPwr12V The basic circuit is similar to that published in MagPi October 2012. I added a PIC microcontroller to the circuit to help in powering down or powering up of the Raspberry Pi. The microcontroller has its ow...
by hampi
Fri Oct 25, 2013 9:27 am
Forum: Other projects
Topic: 12v Li-ion charging circuit?
Replies: 14
Views: 7075

Re: 12v Li-ion charging circuit?

You could easily add a 12V relay in cicruit so that the output side of the battery is disconnected whenever the main 12V charge voltage is present. Probably easier to use power diodes for switching. Usually the voltage that is used for charging the battery needs to be higher than the voltage on the...
by hampi
Thu Oct 24, 2013 8:12 pm
Forum: Other projects
Topic: 12v Li-ion charging circuit?
Replies: 14
Views: 7075

Re: 12v Li-ion charging circuit?

A circuit to activate the recharge only when the battery was below a certain level would be nice - I'll have look into zener diodes and fet transistors and brush up on my electronics! That is a comparator circuit switching a transistor on/off. In addition to the operational amplifiers you can find ...
by hampi
Sun Oct 20, 2013 5:13 pm
Forum: Other projects
Topic: 12v Li-ion charging circuit?
Replies: 14
Views: 7075

Re: 12v Li-ion charging circuit?

I do not know but reading the battery university looks like a microcontroller project. See the link

http://batteryuniversity.com/learn/arti ... _batteries
by hampi
Mon Oct 14, 2013 5:55 pm
Forum: Other programming languages
Topic: Version control
Replies: 30
Views: 4683

Re: Version control

jamesh wrote:As far as I can tell its all set up correctly, the right remotes etc, BUT IT JUST REFUSES TO DO IT.
What does a copy-and-paste of the error message to google say?
by hampi
Mon Oct 14, 2013 2:15 pm
Forum: Other programming languages
Topic: Version control
Replies: 30
Views: 4683

Re: Version control

The svn is is centralized and git/hg distributed. I have not used hg so far. Maybe some day.
by hampi
Mon Oct 14, 2013 12:31 pm
Forum: Other programming languages
Topic: Version control
Replies: 30
Views: 4683

Re: Version control

IMHO if you have never used any version control svn is a good start and later when you are wiser you will probably want to use git. The two ideas are quite different, but it also depends on the kind of data that is in the repository and who (if anybody) is using it.
by hampi
Sun Oct 13, 2013 8:49 am
Forum: Other projects
Topic: 100% solar powered Pi?
Replies: 8
Views: 44765

Re: 100% solar powered Pi?

I am debugging the daemon code for my DIY power supply now https://github.com/oh7bf/RaspiPwr12V/wiki With this power supply you should be able to go to sleep mode and the Raspberry Pi does not need to run continuously. That should save some money in the investment to the solar panel and battery. The...
by hampi
Tue Sep 24, 2013 9:59 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: GPIO and flip flops??
Replies: 6
Views: 2932

Re: GPIO and flip flops??

The PiPIC can detect long enough low signal or key pressing. The event register needs to be read with i2c from the PiPIC to find out if any of the keys (maximum 4 with pic12f675) have been pressed.

https://github.com/oh7bf/PiPIC/wiki
by hampi
Tue Sep 24, 2013 3:31 pm
Forum: HATs and other add-ons
Topic: Power supply module against violent power-off
Replies: 3
Views: 2145

Re: Power supply module against violent power-off

A 12 V sealed battery with USB cigarette lighter adapter is fairly easy and safe solution. The lead acid battery provides the uninterruptible power. Reducing the current ~70 mA in halt mode might be important in solar powered application, but otherwise the battery charge could be maintained from mai...
by hampi
Mon Sep 23, 2013 9:05 am
Forum: Automation, sensing and robotics
Topic: DIY lipo low voltage alarm
Replies: 17
Views: 7218

Re: DIY lipo low voltage alarm

Strangely enough I am preparing to get on the same issue, too, but I took completely different path: I am, currently, coding for i2c slave for AVR processors and my idea is to use their ADCs to monitor battery voltage directly. That is similar to what I am testing now for a 12 V SLAB https://github...
by hampi
Sat Sep 21, 2013 4:11 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Raspberry Pi PIC Programmer using GPIO
Replies: 102
Views: 46839

Re: Raspberry Pi PIC Programmer using GPIO

Newton wrote:After using it for while, it suddenly stopped working correctly.
Most likely bad connection somewhere. Disconnect wires and reconnect them again.
by hampi
Fri Sep 06, 2013 11:34 am
Forum: HATs and other add-ons
Topic: how to sense 220v input -solved- I hope
Replies: 59
Views: 58325

Re: how to sense 220v input -solved- I hope

I was thinking about capacitive sensing too, but then it still needs a ground (neutral) connection if I understand correctly. Or is the circuit self-capacitance (or displacement current) enough?
by hampi
Mon Aug 12, 2013 8:30 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: PiPIC project
Replies: 0
Views: 403

PiPIC project

I started a project to program a custom i2c chip to the Raspberry Pi. This way it should be possible to put a few different functions on the same chip thus reducing the number of components on the external PCB. The PIC12F675 seems to be easily available for the hobby builders and is not too expensiv...
by hampi
Sun Aug 11, 2013 9:09 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Interfacing troubleshooting
Replies: 2
Views: 646

Re: Interfacing troubleshooting

For the well known "standard" chips reading the datasheet should be enough. Can also start first with the easy ones like the 8-bit I/O expander PCF8574. The expander output can be checked with a multimeter or by wiring LEDs to the outputs. For debugging a bit banged i2c on software you will probably...
by hampi
Mon Aug 05, 2013 9:20 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: I2C Speed
Replies: 2
Views: 1920

Re: I2C Speed

The line

options i2c_bcm2708 baudrate=35000

should be in file

/etc/modprobe.d/i2c.conf
by hampi
Fri Aug 02, 2013 2:02 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: hook two raspberries using I2C
Replies: 8
Views: 1747

Re: hook two raspberries using I2C

Two i2c masters (or two Pi's) on the same bus sharing one or two i2c slave registers?
by hampi
Wed Jul 24, 2013 12:01 pm
Forum: General discussion
Topic: Using Raspberry Pi via Windows
Replies: 9
Views: 1446

Re: Using Raspberry Pi via Windows

Yes you can install putty, xming and winscp to the Windows machine.

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