You could use an IO expander module (e.g. PCF8575 or MCP23017) between the Pi and the relay board: those modules don't change pin states unless they receive a valid I2C/SPI command, so they will not be affected by sporadic pin toggling at boot.
You'll have to enable the correspoding interface (I2C or SPI) on the Pi to be able to talk to the expander.
This is a JTAG connector used for development and testing. Here's a picture of an old Pi B+ featuring the signal names printed on it:
AFAIK it's useless unless you have VideoCore documentation and tools from Broadcom.
To step down the battery voltage, you need a buck converter. Adding the "boost" feature reduces efficiency, adds cost & complexity with no benefit.
The converter you've found on that website is unfortunately typical of the trash they push on the gullible - it has "disappointment" written all over it. The seller's description is ...
It's 2020 and I know the question was asked a long time ago.
We like to use the rpi for an industry application (process monitoring)
Nobody can stop you from doing so, there might be better but also worse alternatives depending on the task at hand. As for the questions:
1. power supply from 24-48 volt
Search: "din rail dc power 5V" (you don't want ...
To add to what @Ingo said, they actually have a third OUI now: E4-5F-01
Not sure why that happened either, but I have hardware with a MAC with that OUI.
I'd have commented that, but don't have enough reputation.
This is an old question, but there are new answers:
The original question will soon be 10 years old, and the "official documentation" quoted in the currently accepted answer has been revised. The RPi FAQ is in the same location, but the relevant FAQ is now here: What is its operating temperature? Does it need a heatsink? But this FAQ is not ...
Yes - you can definitely do that. Two things you must keep in mind:
The RPi and the external battery-powered hardware must operate at a common reference potential. This is easily accomplished by connecting the two GROUND points together.
RPi GPIO pins are biased at 3.3V, and they are rather fragile. You must properly interface them to your external ...
In general, yes this is possible.
You must connect the grounds of both power supplies together at some point.
You must also make sure that no 5 V logic signals that come from your 5 V logic are connected to pins on the Pi, as this can permanently damage the Pi. There is no danger of damage if GPIO outputs from the Pi are connected to logic inputs in the 5 V ...
Using openssl and public private keys,
You could get the pi serial number and encrypt it with a private key, place it on the sd card along with the public key.
If you decrypt the file with the public key and the serial numbers don't match then you stop it running.
The serial numbers may not be unique but it's a good place to start.
Common sense would be that children who are too young to understand or be responsible for the issues involved with handling a bare board should be closely supervised (or just plain told they are too young).
The major risk here is not harm to the child, but damage to the board. As per other comments, use of lead solder was banned in the EU in 2006:1
All Pi SOC have a One-Time Programmable (OTP) memory block, indeed this is where the Serial Number resides.
See OTP register and bit definitions although as goldilocks pointed out security through obscurity has its limits.
You CAN power external components; indeed for some this is recommended.
It is (generally) essential to share Gnd connections (opto-isolated devices are a possible exception).
There is actually no need in this case, as the Pi 5V can easily supply the current needed by 2 relay coils.
HOWEVER if you are using a relay module similar to that pictured they are ...
It's not clear from your question that you need to measure current. As a practical matter, measuring voltage is often easier.
@Dougie comment suggesting an [opto-coupler (a.k.a. opto-isolator)] is a good one as it provides galvanic isolation - an important safety consideration working with mains voltages. As you've seen in the comments, there are various ...
Errno 121 usually occurs when running an I2C python program with the following situation:
2.1 The hardware wiring connection is bad, eg,
2.1.1 Forget to plug/connect the cable,
2.1.2 Too long cabling, eg, over 30cm,
2.1.2 I2C frequency too high, over 400kHz,
2.1.3 I2C device, eg. I2C I2C MCP23017, which is sensitive to noise,
2.1.4 I2C bus overloaded, ...
if you use ALSA then this command should help you:
when nothing is playing the output is "closed"
but when something is played it shows i.e. like this:
22:21:52 pi@sabaj-d5:~ $ cat /proc/asound/card*/pcm*p/sub*/hw_params
rate: 44100 (...
It appears you have shorted the two ends of the resistor - this is not what you want to do.
Breadboards (a.k.a. "solderless breadboards") are really simple, but like all simple things, you must invest some effort to understand how they are constructed. That means you'll need to know that the breadboard is actually just a series of metal clips (...
In the Bluetooth spec there is no limit on the number of connections that can be made. However, in the real world, the Bluetooth hardware has constrained resources that have a practical limit to the number of simultaneous connections that can be maintained. By adding additional radios (USB dongles) then you should be able to raise the number of supported ...
LoRa is NOT intended to be used for such a thing. LoRa operates in the free ISM band. As such there are rules that don't allow transmission over a long period (the maximum allowed transmission time is regulated by the local government) in order to allow other devices to also use the shared medium - thus reducing the air-time. Also LoRa uses transmission ...
The charger you have asked about should be fine. The USB-C specifications allow the higher voltage levels, and a "signaling mechanism" that is part of the USB-C standard guarantees that as long as the device (your RPi) and the power supply both adhere to the standards, things will work as they should.
That said: The first RPi4 production units were ...
This is a simple programming Question, not specific to the Pi.
It appears to be the python equivalent of the ?= conditional expression
There appears to be nothing unusual, although clever programming tricks like this just make code like this difficult to maintain.
It would be clearer if the author used parentheses.
NOTE In this particular case it is not ...
The only answer on here (at time of writing) is a little outdated (7 years old)
What you're proposing is impossible
It's certainly not - in fact someone has already done this
Finally, even assuming you could somehow interface the Pi to the
surviving PowerBook internals, your new creation would not be nearly
as fast as the original PowerBook. I talk about ...
Have you considered the PI Zero? I run them from 12V batteries no issue. They use about 1Ah per day, so a 5Ah battery with a small solar panel would have tons of overhead. As for suspend to RAM, do you mean suspend to SD card? I think that sleeps of 100ms would be a better option.
The other thing you could consider is the Arduino solutions like Wemos. These ...