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by PiGraham
Fri Aug 18, 2017 4:52 pm
Forum: General discussion
Topic: Turning on Zero W every hour
Replies: 33
Views: 2462

Re: Turning on Zero W every hour

@artpy VERY interesting project ! You should write a blog post ! I'm suprised you only have 5days uptime, 1200mAh / 0.8 shoud gives you 62 days ? The 1min boot every hour seem to suck lot's of power ? Do you have some update with the PiZero W and the Solar Panel ? Do you have enought power (indoor)...
by PiGraham
Fri Aug 18, 2017 2:53 pm
Forum: General discussion
Topic: Pi Zero power consumption with e-ink display
Replies: 3
Views: 139

Re: Pi Zero power consumption with e-ink display

You could use a UPS style board that can power-on by a timer. e.g. https://spellfoundry.com/product/sleepy-pi/ Or one of various wak-up timer boards: https://blog.adafruit.com/2017/03/09/new-product-adafruit-tpl5110-low-power-timer-breakout/ Or even something basic like this: https://www.amazon.co.u...
by PiGraham
Fri Aug 18, 2017 11:09 am
Forum: Advanced users
Topic: HDMI audio via HDMI to RCA lead possible?
Replies: 3
Views: 98

Re: HDMI audio via HDMI to RCA lead possible?

Above suggestions look good. You could also use an HDMI to VGA converter with audio out. I have one that works with Pi but it was and anonymous eBay product no longer listed. They are mostly cheap enough to buy to try. A possible advantage of using a VGA adaptor is better quality display if you shou...
by PiGraham
Fri Aug 18, 2017 10:31 am
Forum: General discussion
Topic: How to post image in the forum?
Replies: 12
Views: 335

Re: How to post image in the forum?

ujjwalrathod007 wrote:
Fri Aug 18, 2017 10:27 am
Image

Now it works I guess
Too many img tags

Code: Select all

[img][img]http://i.imgur.com/iR84RBB.png[/img][/img]
should be:

Code: Select all

[img]http://i.imgur.com/iR84RBB.png[/img]
by PiGraham
Thu Aug 17, 2017 3:06 pm
Forum: Graphics, sound and multimedia
Topic: Automated panorama photo
Replies: 12
Views: 527

Re: Automated panorama photo

Not bad. I wonder if you could reduce the jaggies with some alpha masking.
Maybe composite the image with pillow.

Code: Select all

PIL.Image.composite(image1, image2, mask)[source] 
https://pillow.readthedocs.io/en/3.0.0/ ... Image.html
by PiGraham
Thu Aug 17, 2017 11:57 am
Forum: Graphics, sound and multimedia
Topic: Automated panorama photo
Replies: 12
Views: 527

Re: Automated panorama photo

The results look good. Ideal for static scenes. How do the full-res images look?
by PiGraham
Tue Aug 15, 2017 5:40 pm
Forum: Beginners
Topic: Reusing an old tablet LCD display - having issues
Replies: 3
Views: 210

Re: Reusing an old tablet LCD display - having issues

There seem to be plenty of LCD drivers still on eBay

You can get a 15" high res creen working for similar price to a 3.5 inch low res TFT. If you have the screen you might as well use it.
by PiGraham
Tue Aug 15, 2017 3:45 pm
Forum: Troubleshooting
Topic: Serial output only 8 chars
Replies: 3
Views: 110

Re: Serial output only 8 chars

but I still get the echo back. How to I get rid of the echo? I'm not clear where you are seeing echo. You had a loopback connection (Rx to Tx) Have you removed the loopback connection and are you still seeing transmitted characters being received back? Are you running terminal software and typing a...
by PiGraham
Tue Aug 15, 2017 1:49 pm
Forum: Advanced users
Topic: Data is not instantly written in SD card
Replies: 25
Views: 615

Re: Data is not instantly written in SD card

But the OS takes care of all that anyway. Just write 170 bytes once a minute, or one byte every 3 seconds or whatever variation you like and it gets cached and the OS burns it into FLASH every 4k/ 24 4mins. From the original question: But the data is not written in the SD CARD instantly. It waits u...
by PiGraham
Tue Aug 15, 2017 11:13 am
Forum: Advanced users
Topic: Data is not instantly written in SD card
Replies: 25
Views: 615

Re: Data is not instantly written in SD card

Probably not obvious to Baakinira who only has 170 bytes/min (4k/24 mins) of data coming in and, for reasons we don't yet know, wants to write to physical FLASH more frequently than is sensible. Thats 4080 bytes every 24 minutes. how about something like this (in silly C style pseudo code!) char bu...
by PiGraham
Tue Aug 15, 2017 10:54 am
Forum: Advanced users
Topic: Data is not instantly written in SD card
Replies: 25
Views: 615

Re: Data is not instantly written in SD card

Until we know what the problem is it's hard to suggest a good solution, but fsync for each tiny data packet is probably a bad idea. There's a reason for the 4k size. Obviously. Probably not obvious to Baakinira who only has 170 bytes/min (4k/24 mins) of data coming in and, for reasons we don't yet ...
by PiGraham
Tue Aug 15, 2017 10:35 am
Forum: Advanced users
Topic: Data is not instantly written in SD card
Replies: 25
Views: 615

Re: Data is not instantly written in SD card

Until we know what the problem is it's hard to suggest a good solution, but fsync for each tiny data packet is probably a bad idea. There's a reason for the 4k size. Sync'ing to FLASH each time you have a new sensor reading will not be efficient use of storage. fsync before shutdown to preserve data...
by PiGraham
Tue Aug 15, 2017 10:18 am
Forum: Troubleshooting
Topic: Serial output only 8 chars
Replies: 3
Views: 110

Re: Serial output only 8 chars

What do you do between writing test data and calling the read function? Do you wait for the data to get clocked onto the wire? As Joan pointed out on the other topic: You are sending data along a serial link. It takes time. You need to put a delay between the send and receive. Presumably the natural...
by PiGraham
Tue Aug 15, 2017 7:51 am
Forum: Advanced users
Topic: Data is not instantly written in SD card
Replies: 25
Views: 615

Re: Data is not instantly written in SD card

Using /tmp is really not a good idea *unless* you clean up after yourself and accept the fact that it is volatile. As davidcoton pointed out the OS disk caching handles write-read anyway and does the clean-up and flushing automatically so use of ramfs is not useful here anyway. Hopefully Baakinira ...
by PiGraham
Mon Aug 14, 2017 7:48 pm
Forum: Graphics, sound and multimedia
Topic: Automated panorama photo
Replies: 12
Views: 527

Re: Automated panorama photo

There are ways to Compromise quality for speed. Have you seen this?
https://www.raspberrypi.org/magpi/build ... 60-camera/

180° should be possible using a cylindrical or conical mirror.
by PiGraham
Mon Aug 14, 2017 4:29 pm
Forum: Graphics, sound and multimedia
Topic: Automated panorama photo
Replies: 12
Views: 527

Re: Automated panorama photo

gordon77 wrote:
Mon Aug 14, 2017 3:14 pm
I experimented with a 200 step stepper motor and HAT from adafruit..
That looks like a nice result. How long does it take?
by PiGraham
Mon Aug 14, 2017 4:27 pm
Forum: Graphics, sound and multimedia
Topic: Automated panorama photo
Replies: 12
Views: 527

Re: Automated panorama photo

OpenCV will stitch overlapping images and that should run on a Pi.

Here is one blog about OpenCV panoramas with Python.
http://www.pyimagesearch.com/2016/01/11 ... stitching/
by PiGraham
Mon Aug 14, 2017 3:27 pm
Forum: Troubleshooting
Topic: Really bad composite video out on Pi 3?
Replies: 27
Views: 839

Re: Re:I Really bad composite video out on Pi 3?

TVs often had a designated VCR channel button which shortened the time constant of the horizontal loop to better track the timing variations caused by the mechanics of the replay process. That's a fair point since this is from the end of the VCR era, a CRT (reviews from 2007?) with digital circuitr...
by PiGraham
Mon Aug 14, 2017 11:49 am
Forum: General discussion
Topic: IVPort Dual camera multiplexer
Replies: 15
Views: 1116

Re: IVPort Dual camera multiplexer

with a 17Ah SLA battery installed in a 35x25x15cm cabinet I'm only guessing here but I wonder if the OP's need for battery is for handheld operation, maybe some sort of 360° camcorder or something. SLA is still a reliable workhorse for many applications but a seriously heavy brute for anything you ...
by PiGraham
Mon Aug 14, 2017 10:19 am
Forum: Advanced users
Topic: Data is not instantly written in SD card
Replies: 25
Views: 615

Re: Data is not instantly written in SD card

If you need to do something with the data you could write it to a file in ramdisk (e.g. in /tmp directory) as often as you like and read it from there for most recent values. That shouldn't be an issue. Any read operation will know about the cache, readings there will be treated the same as ones ac...
by PiGraham
Mon Aug 14, 2017 9:19 am
Forum: Advanced users
Topic: Data is not instantly written in SD card
Replies: 25
Views: 615

Re: Data is not instantly written in SD card

I actually want to collect data every 1 minute but if I insert delay of 1 minute, it takes 24 minutes to collect 4kb data which is not good. It's this the problem of raspberry pi or the sd card? What is not good about that? Are you concerned that data may be lost of power fails? Do you need to acce...
by PiGraham
Mon Aug 14, 2017 8:15 am
Forum: Troubleshooting
Topic: Really bad composite video out on Pi 3?
Replies: 27
Views: 839

Re: Really bad composite video out on Pi 3?

AFAIK any NTSC TV is a 480i device and will display two interlaced fields no matter what you feed it. Not true. I won't say that the following applies to all NTSC TVs but it certainly applies to many if not the vast majority. It definitely applies to the purely analogue, CRT based ones with no digi...
by PiGraham
Sun Aug 13, 2017 9:47 pm
Forum: General discussion
Topic: IVPort Dual camera multiplexer
Replies: 15
Views: 1116

Re: IVPort Dual camera multiplexer

... USB camera with compression hardware built in ... ... Compute modules. Each can directly interface to two PI CSI cameras ... ... One PiZero per camera might be viable ... All good ideas, but I cannot see why any of them are better than the IVPort/Arducam option? Just options. Not saing any are ...
by PiGraham
Sun Aug 13, 2017 8:53 pm
Forum: General discussion
Topic: IVPort Dual camera multiplexer
Replies: 15
Views: 1116

Re: IVPort Dual camera multiplexer

Cost is not an issue, power consumption is. Besides, I want more than two cameras. Four at least. You could use compressed video into USB either from a USB camera with compression hardware built in, or as a separate unit. You should be able to do more than four cameras that way but they are signifi...
by PiGraham
Sun Aug 13, 2017 8:39 pm
Forum: Troubleshooting
Topic: Really bad composite video out on Pi 3?
Replies: 27
Views: 839

Re: Really bad composite video out on Pi 3?

Why do you mention 240p? Surely you need 480i for NTSC, typically 640 x 480 interlaced. Because it's better for older games. NES for example only outputs 240p, so trying to force it to be 480i just worsens the images as it has to stretch it out and it ends up being flickery, while 240p is not flick...

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