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by rzusman
Sun Oct 29, 2017 11:27 pm
Forum: Compute Module
Topic: [SOLVED] Enc28j60 takes both SPI Chip Selects on CM3 (and CM1)!
Replies: 2
Views: 1230

Re: Enc28j60 takes both SPI Chip Selects on CM3 (and CM1)!

Never mind.

My mistake - the enc28j60 driver is taking CE0, and that is on GPIO pin 8. I was confused and thought that it was taking CE1 (on GPIO 7). So, the fact that /dev/spidev0.1 is the only device available makes sense.
by rzusman
Sun Oct 29, 2017 4:55 am
Forum: Compute Module
Topic: [SOLVED] Enc28j60 takes both SPI Chip Selects on CM3 (and CM1)!
Replies: 2
Views: 1230

[SOLVED] Enc28j60 takes both SPI Chip Selects on CM3 (and CM1)!

I've been trying to get my SPI code working, with very little luck. I am using CS 0 to talk to a micro-controller, and CS 1 to talk to the ENC28J60 Ethernet port. No matter what I tried, I could not get CS0 to work - in fact there was no entry in /dev for SPI0.0 - only SPI0.1 I finally had the thoug...
by rzusman
Sat Oct 28, 2017 11:27 pm
Forum: Compute Module
Topic: Pull ups in SPI?
Replies: 1
Views: 1010

Re: Pull ups in SPI?

I am using an ENC28J60 module (from ebay) on my Compute Module, and it works fine with no pullups.
However, I am powering the CM's busses from 3.3v - are you using 1.8v?
by rzusman
Sat Sep 23, 2017 11:10 pm
Forum: Compute Module
Topic: CM3 Can't Access SD Card on Custom Board
Replies: 2
Views: 1058

Re: CM3 Can't Access SD Card on Custom Board

Your schematic looks like mine, except I simply tied pin 2 (/EMMS_DISABLE) to +3.3V.

I didn't take any particular precaution about keeping my traces all the same length, although they are all pretty short (< 2"). Are you sure that /EMMS_DISABLE is high? Scope it and see.
by rzusman
Tue Sep 19, 2017 4:43 am
Forum: Automation, sensing and robotics
Topic: RS485 Pi to PC
Replies: 3
Views: 1713

Re: RS485 Pi to PC

It's unlikely to be a biasing problem, if your RS-485 converter is well designed, but it's possible. Here is an article that talks about it: http://blog.opto22.com/optoblog/rs-485-to-terminate-bias-or-both As for the scope - I don't have any experience with the pico scope, but I highly recommend Sal...
by rzusman
Mon Sep 18, 2017 2:20 am
Forum: Automation, sensing and robotics
Topic: RS485 Pi to PC
Replies: 3
Views: 1713

Re: RS485 Pi to PC

I have done a lot of work with RS-485, and most of the problems can be traced to:
1) Bad timing on the “turnaround” line (transmit enable to receive enable).
2) Bad biasing, so the the idle state is floating, and the stop bit is never detected.

You really need to use a scope to see what is going on.
by rzusman
Mon Sep 18, 2017 2:01 am
Forum: Other projects
Topic: IR receiver input problem (simple IR tripwire project)
Replies: 1
Views: 1153

Re: IR receiver input problem (simple IR tripwire project)

The problem is, the TSOP38238 is not a receiver diode - it’s a tuned IR receiver, and will only accept bursts of IR at around 38KHz. If you want to use this (it’s a good device for this application), you need to modulate (pulse) your LED at 38KHz. Basically, send bursts of 38KHz on/off light to the ...
by rzusman
Sun Sep 17, 2017 10:49 pm
Forum: C/C++
Topic: interrupt o multithreading
Replies: 3
Views: 912

Re: interrupt o multithreading

It all depends on how fast you need to read the ADC. If you only need to read it every second, just blink the LED, read the ADC, plot the data, and sleep for another second. Multithreading isn’t going to help here. Multithreading only helps if you want to do two asynchronous tasks at what appears to...
by rzusman
Sun Jul 23, 2017 3:51 am
Forum: Automation, sensing and robotics
Topic: UART port
Replies: 2
Views: 574

Re: UART port

Depending on the baud rate, you can “bit-bang” a serial port on regular GPIO.

Raspberry Pi’s < 3 have two serial ports available. The 3 only has one (the other is used for bluetooth).
The Compute Modules have two serial ports. I am using one at 115,200 Baud and one at 9,600 baud.
by rzusman
Tue Jul 18, 2017 11:38 pm
Forum: Troubleshooting
Topic: Possible to connect to pi via USB?
Replies: 4
Views: 707

Re: Possible to connect to pi via USB?

Use a Terminal Emulator and the UART on the Pi.
by rzusman
Tue Jul 18, 2017 11:37 pm
Forum: General programming discussion
Topic: Encrypt SD card content
Replies: 41
Views: 40020

Re: Encrypt SD card content

The Compute Module has embedded Flash, so that makes it a whole lot harder for the casual user to copy your software.
by rzusman
Mon Jul 17, 2017 4:22 am
Forum: Beginners
Topic: 4 digits 7 segments
Replies: 7
Views: 1337

Re: 4 digits 7 segments

You need to scope the outputs to determine exactly what is happening, but I’d bet that the rise or fall times of your outputs are too slow, and so multiple transistors are being turned on.

Posting your schematic would help.
by rzusman
Mon Jul 17, 2017 4:11 am
Forum: Advanced users
Topic: Pi and Meanwell ELG-100-C1050B AC
Replies: 1
Views: 525

Re: Pi and Meanwell ELG-100-C1050B AC

You need an external circuit to create the dimming signal.
0-10V PWM is probably the simplest - that would only require a single FET transistor and a resistor, and the Pi to emit the PWM signal (which Joan’s pigpio library can do). Oh, and a 10v power supply.
by rzusman
Sat May 13, 2017 9:48 pm
Forum: General discussion
Topic: Awesome Siri Hack!
Replies: 2
Views: 1001

Re: Awesome Siri Hack!

I can think of something to use this for right away, but I won't have the time to test it for quite awhile.

Neat project, though!
by rzusman
Sat May 13, 2017 6:46 pm
Forum: General discussion
Topic: Using RPi3 in pressure compensated (oil-filled) enclosure?
Replies: 8
Views: 1281

Re: Using RPi3 in pressure compensated (oil-filled) enclosur

In the interest of accuracy, I should point out that my previous post was not 100% correct. There are some parts that have voids in them - high-end processors, for example (like the intel Core i7). And, of course, devices like accelerometers and oscillators. But, even those would probably stand 100 ...
by rzusman
Sat May 13, 2017 2:09 pm
Forum: General discussion
Topic: Using RPi3 in pressure compensated (oil-filled) enclosure?
Replies: 8
Views: 1281

Re: Using RPi3 in pressure compensated (oil-filled) enclosur

I have to ask - why? I'm curious as to the background behind your question. My first thought is that, whilst most component parts seem solid, I doubt they really are. They'll possibly be a silicon wafer with) wires connecting to the pins, encapsulated in a plastic or ceramic 'box'. The remaining sp...
by rzusman
Tue May 09, 2017 3:09 am
Forum: Beginners
Topic: Trouble with first time using wiringPi
Replies: 3
Views: 500

Re: Trouble with first time using wiringPi

If you mean Broadcom port #16, that is used by the UART by default.
by rzusman
Fri May 05, 2017 10:25 pm
Forum: Beginners
Topic: Trouble with first time using wiringPi
Replies: 3
Views: 500

Re: Trouble with first time using wiringPi

Put \n at the end of your printf statement.

The characters won't be echoded without it unless they are explicitly flushed.
by rzusman
Tue May 02, 2017 4:23 am
Forum: Troubleshooting
Topic: Pneumatics with Raspberry Pi
Replies: 3
Views: 532

Re: Pneumatics with Raspberry Pi

The relays control the valves. The valves just have solenoids in them, and you switch the relays on and off to activate the solenoids. The relay board you linked to requires one gpio per relay, so you will need to dedicate a bunch of pins to controlling the board. If you wanted to use a microcontrol...
by rzusman
Tue May 02, 2017 4:17 am
Forum: Beginners
Topic: How fast can the GPIO be?
Replies: 4
Views: 636

Re: How fast can the GPIO be?

You might want to check out the speed differences between C and Python here:
http://www.spazztech.net/python-vs-c-on-rpi.html
by rzusman
Sun Apr 23, 2017 8:35 pm
Forum: Astro Pi
Topic: Sideral time
Replies: 2
Views: 1785

Re: Sideral time

Use the “Hello_pi” demo programs as a starting point.
by rzusman
Fri Apr 21, 2017 7:28 pm
Forum: Advanced users
Topic: Read 74HC595 State?
Replies: 4
Views: 1053

Re: Read 74HC595 State?

Why do you need to read the state? You should know the state.

If you are driving the shift register, than your software should already know the state of the outputs, otherwise you would be turning on the wrong output.
by rzusman
Fri Apr 21, 2017 6:59 pm
Forum: General discussion
Topic: Rpi 0 number of threads
Replies: 10
Views: 1172

Re: Rpi 0 number of threads

Frybo wrote:Now does arm have threads
What does this mean?
by rzusman
Mon Apr 17, 2017 2:25 am
Forum: General discussion
Topic: Smart irrigation system
Replies: 11
Views: 4850

Re: Smart irrigation system

You should be able to do what you want with a relay and transistor driver, a 12v pump (look in a car junkyard for a windshield washer pump), and a moisture sensor, which can just be two stainless-steel wires connected to an OpAmp comparator circuit. I'm not going to design this for you - there's a t...

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