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by mikronauts
Tue Jun 25, 2019 2:34 am
Forum: General discussion
Topic: Raspberry Pi 4 Thread - general discussion
Replies: 279
Views: 12232

Re: Raspberry Pi 4 Thread - general discussion

Thanks, I will keep checking. Great news indeed! I ordered two boards - a 1GB, and a 2GB board, however I cannot find a 4GB board in stock in Canada, US, or UK. Please post here if you know any place eith 4GB in stock. Btw the additional i2c and uarts are great for my purposes. Last I check, the 4GB...
by mikronauts
Mon Jun 24, 2019 8:06 pm
Forum: General discussion
Topic: Raspberry Pi 4 Thread - general discussion
Replies: 279
Views: 12232

Re: Raspberry Pi 4 Thread - general discussion

In low quantities, yes. Personally I ordered a few thousand nylon washers, nuts, screws and various height standoffs from a manufacturer for my boards. Price was ok. Shipping took a while. Did anybody complain about the M2.5 mounting holes (same as on previous models) yet? I can do that if you want ...
by mikronauts
Mon Jun 24, 2019 7:52 pm
Forum: General discussion
Topic: Raspberry Pi 4 Thread - general discussion
Replies: 279
Views: 12232

Re: Raspberry Pi 4 Thread - general discussion

Great news indeed!

I ordered two boards - a 1GB, and a 2GB board, however I cannot find a 4GB board in stock in Canada, US, or UK.

Please post here if you know any place eith 4GB in stock.

Btw the additional i2c and uarts are great for my purposes.
by mikronauts
Sun Jun 16, 2019 4:53 pm
Forum: General discussion
Topic: Running 3 RC522 side by side continuously
Replies: 14
Views: 396

Re: Running 3 RC522 side by side continuously

Best guess: insufficient power Well I posted this as a new thread in troubleshooting, but it got removed and I'm not sure why. Anyways, I got the code to work, and I can run any two of my RC522 together. However, the moment I even just wire the third one in, everything stops working - the two workin...
by mikronauts
Thu Jun 13, 2019 5:24 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: How 2nd UART based on I2C, SPI or USB ?
Replies: 2
Views: 218

Re: How 2nd UART based on I2C, SPI or USB ?

Just get a cheap usb serial device. Can you guide me? I'm looking for a 2nd hardware based serial interface available. I would like to avoid software based solutions and simply look for an existing HAT or e.g. USB2UART which provides a 2nd set of TX/RX signals. Google offers a lot but the results ar...
by mikronauts
Thu Jun 13, 2019 5:20 pm
Forum: General discussion
Topic: Running 3 RC522 side by side continuously
Replies: 14
Views: 396

Re: Running 3 RC522 side by side continuously

Easiest: - get three usb ttl adapters (or 2 plus pi gpio serial) - mod rc522 for serial instead of spi - use a separate thread per port See https://forum.arduino.cc/index.php?topic=442750.0 On modding So, here's a synopsis of what I am trying to do. I want to put 3 RC522 RFID readers side by side in...
by mikronauts
Tue Jun 04, 2019 3:03 pm
Forum: Automation, sensing and robotics
Topic: RS-232C Terminal to remotely control receiver volume. Can I do that?
Replies: 5
Views: 160

Re: RS-232C Terminal to remotely control receiver volume. Can I do that?

You could also use an ir led and lirc. Hi, guys, I'm wondering if there is a way to remotely control the volume on my stereo receiver using a raspberry pi connected to the receiver's RS-232C terminal. If anyone has any ideas or can direct me to someone or a site that can help, I would truly apprecia...
by mikronauts
Mon May 20, 2019 1:28 am
Forum: Beginners
Topic: RS485 HAT
Replies: 2
Views: 158

Re: RS485 HAT

A usb adapter is your best bet.
Shaimaa Badr wrote:
Sun May 19, 2019 10:35 am
I don't find RS485 HAT shield here in Egypt,, Can I use IC MAX485 and any help for how to connect with raspberry pi to the device has a rj45 socket or use CH340 USB to RS485 485 Converter Adapter Module??!
by mikronauts
Tue May 14, 2019 9:56 pm
Forum: General discussion
Topic: RPi high school lab. B+ issues. B no issues.
Replies: 24
Views: 1129

Re: RPi high school lab. B+ issues. B no issues.

Very frustrating. I am beginning to suspect those Pi's may have been zapped. Given the amount of time you have invested so far, perhaps get one or more new 3b+'s? Fortunately they are cheap. Or, break out the test gear... I would suspect an issue with the 3v3 regulation, or poor connection in the sd...
by mikronauts
Fri May 10, 2019 1:16 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Microchip/mcu
Replies: 7
Views: 450

Re: Microchip/mcu

Right now, I think an arduino nano 3 clone would probably suit you. Cheap, usb, tons of tutorials. You will have to learn how to communicate with it. You need to be more precise: "can expand my GPIO with 5" is meaningless. 5 what? Hi All, I'm searching for an microchip or mcu that can expand my GPIO...
by mikronauts
Mon May 06, 2019 3:57 pm
Forum: C/C++
Topic: BCM2835 library, I'm after 1 to 20 microsecond delays but needn't be very accurate
Replies: 7
Views: 1194

Re: BCM2835 library, I'm after 1 to 20 microsecond delays but needn't be very accurate

The diagram suggests that using an inverted CSEL as ST_CP, CLK & MOSI should work for your shift register. The shift registers I write to aren't SPI devices. They don't have MISO, MOSI,CSEL... pins. They just have a serial in pin, a clock pin and an enable pin. They take data according to the attace...
by mikronauts
Sun May 05, 2019 4:15 pm
Forum: General discussion
Topic: SPI speed and ADC sampling rate
Replies: 3
Views: 188

Re: SPI speed and ADC sampling rate

You are most welcome. Python is an interpreted language, with garbage collection, and not well suited to regular, precisely timed sampling. Writing your app in C would make the timing more predictable. You can improve your python code somewhat by: - use an integer array (not list) for storing the sa...
by mikronauts
Fri May 03, 2019 1:17 pm
Forum: General discussion
Topic: SPI speed and ADC sampling rate
Replies: 3
Views: 188

Re: SPI speed and ADC sampling rate

You need to post your code so we can see what you are doing. Use code tags so the indentation is not lost. Most likely causes: - you are not sampling at precise intervals - you are not reading the voltage correctly (sensor output range vs adc input range) - your voltage reference is not stable Hello...
by mikronauts
Tue Apr 30, 2019 5:43 pm
Forum: Other projects
Topic: Looking for recommendations of best place to start a project that needs collaboration
Replies: 4
Views: 276

Re: Looking for recommendations of best place to start a project that needs collaboration

Based on what you wrote, I would suggest starting a Wiki that you would maintain. The best way to get collaborators (IMHO) is to commit to making the project 100% open source, and ask for volunteers here, reddit, twitter etc. Hi all I'd like to start a project to create a Raspberry Pi powered open s...
by mikronauts
Mon Apr 29, 2019 11:02 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: SPI: Problem with fast ADC sampling
Replies: 5
Views: 304

Re: SPI: Problem with fast ADC sampling

Due to Linux, and caching to a lesser degree, you cannot totally get rid of the jitter you are experiencing. The higher the sampling rate, the more apparent the jitter. Add a deterministic high speed micro controller to do the sampling to a large buffer and have it transfer the data to the pi (some ...
by mikronauts
Mon Apr 29, 2019 10:52 pm
Forum: General discussion
Topic: RPi high school lab. B+ issues. B no issues.
Replies: 24
Views: 1129

Re: RPi high school lab. B+ issues. B no issues.

Have you tried swapping the power cables between the good and bad b+'s? Swapping the power adapters? Swapping the sd cards between good and bad? Reducing the sd card lock? Measuring the 5v and 3v3 rails on the gpio header? I have moved two of the problematic B+'s and reinstalled the OS through the N...
by mikronauts
Fri Apr 19, 2019 2:07 am
Forum: General discussion
Topic: Control powerfull pwm fans with Pi
Replies: 11
Views: 883

Re: Control powerfull pwm fans with Pi

Actually that would be enough as 12v * 2a * 2 is 48W
Imperf3kt wrote:
Thu Apr 18, 2019 10:25 pm
mikronauts wrote:
Thu Apr 18, 2019 9:39 pm
Good point, max current is only 2A on the L298.
Well, you can parallel up the inputs and outputs on this chip to make a 4A continuous drive bridge but that's still far short of 40W
by mikronauts
Thu Apr 18, 2019 9:51 pm
Forum: General discussion
Topic: Control powerfull pwm fans with Pi
Replies: 11
Views: 883

Re: Control powerfull pwm fans with Pi

No idea, but as this is interesting, I googled a bit: https://www.ekwb.com/blog/what-is-pwm-and-how-does-it-work/ Shows a four pin pwm fan with the following signals GND, 12v, Tach, PWM Apparently ome fans have a controller that shape the PWM with ramping rising/falling edges. http://forum.arduino.c...
by mikronauts
Thu Apr 18, 2019 9:39 pm
Forum: General discussion
Topic: Control powerfull pwm fans with Pi
Replies: 11
Views: 883

Re: Control powerfull pwm fans with Pi

Good point, max current is only 2A on the L298. Use a cheap L298 driver module, using a 12V power adapter for the fan (one module could handle two independent fans) If you google Raspberry Pi L298 you will find plenty of articles on driving motors like this. That will not work in this case. The fan ...
by mikronauts
Wed Apr 17, 2019 10:13 pm
Forum: General discussion
Topic: Control powerfull pwm fans with Pi
Replies: 11
Views: 883

Re: Control powerfull pwm fans with Pi

Use a cheap L298 driver module, using a 12V power adapter for the fan (one module could handle two independent fans) If you google Raspberry Pi L298 you will find plenty of articles on driving motors like this. I am interested in the same topic. Since my background is not in electrical engineering, ...
by mikronauts
Tue Apr 09, 2019 1:36 pm
Forum: General discussion
Topic: Which motor control board
Replies: 5
Views: 263

Re: Which motor control board

I have used those - and many other - motor driver boards that need to run on 5V and worked fine from a 3v3 gpio signal. The only exceptions are the rare cases where the control signals need. more than5-10ma One of these? https://www.amazon.co.uk/Neuftech-H-bridge-stepper-controller-Raspberry/dp/B01K...
by mikronauts
Sat Mar 30, 2019 2:17 am
Forum: Beginners
Topic: modbus RTU(rs-485)
Replies: 8
Views: 5997

Re: modbus RTU(rs-485)

You are using an rs422 full duplex adapter, and it can only transmit the way you have it connected. If your software can handle discarding a copy of what you transmit, you can probably connect the rx and tx screw terminals togeather. Attaching a pic of my hardware connection.https://drive.google.com...
by mikronauts
Fri Mar 29, 2019 1:47 pm
Forum: Beginners
Topic: modbus RTU(rs-485)
Replies: 8
Views: 5997

Re: modbus RTU(rs-485)

Odds are that you need to use an ioctl to switch DTE or RTS to switch to receiving. Post the link to the specific device you have, they make both full and half duplex adapters. Hi, I have used a DTech Usb 2.0 to RS485 converter but I can only send data to the connected device but not read from it. W...
by mikronauts
Sun Mar 10, 2019 12:56 am
Forum: HATs and other add-ons
Topic: I2C I/O PORT EXPANDER QUESTION
Replies: 37
Views: 1944

Re: I2C I/O PORT EXPANDER QUESTION

The OP does not want to provide details, when I asked he said led's, when I proposed a simple solution for led's he said it was not led's. In my experience, when a poster is not willing to give details, they want to get free design work for their commercial project. I'm working on a project where a ...
by mikronauts
Tue Mar 05, 2019 3:24 pm
Forum: Automation, sensing and robotics
Topic: Ultrasonic sensor readings become unstable
Replies: 7
Views: 454

Re: Ultrasonic sensor readings become unstable

I am amazed it worked as well as it did for you, as triggering the sensor and reading the result over 20m of cable is a bad idea. Put a pi close to the sensor, and have it report the watet level in a loop over wifi or ethernet. Hi, I am using an ultrasonic sensor to measure the water level in an ext...

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