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by rzusman
Wed Mar 07, 2018 11:48 pm
Forum: Compute Module
Topic: CM3 console [Solved]
Replies: 4
Views: 680

Re: CM3 console

Is the CM3 booting?
Can you see the activity light flashing?
by rzusman
Sun Dec 17, 2017 5:51 pm
Forum: Compute Module
Topic: [SOLVED] eMMC not mounting after rpiboot
Replies: 6
Views: 1066

Re: eMMC not mounting after rpiboot

What machine are you using as a host?
by rzusman
Fri Dec 15, 2017 5:42 pm
Forum: Compute Module
Topic: SD card license for 4-bit SD mode
Replies: 4
Views: 696

Re: SD card license for 4-bit SD mode

OK, then why not just use SPI? Is your data rate that fast?
by rzusman
Fri Dec 15, 2017 12:53 pm
Forum: Compute Module
Topic: SD card license for 4-bit SD mode
Replies: 4
Views: 696

Re: SD card license for 4-bit SD mode

I'd like to know how you plan on booting the 2nd CM3L module.

Or, do you mean each CM3L module will have two SD cards?
by rzusman
Sat Dec 09, 2017 10:45 pm
Forum: Compute Module
Topic: EMMC_EN_N to drive LED
Replies: 1
Views: 390

Re: EMMC_EN_N to drive LED

You can use EMMC_EN_N to flash an activity LED, but you should probably drive the LED with a low-threshold FET, like SSM3K329RLFCT-ND (from DigiKey).
This is what I do, and it works fine.
by rzusman
Wed Nov 29, 2017 3:54 am
Forum: Compute Module
Topic: Kernel Crash with GSM Modem AND I2C-0 Enabled
Replies: 3
Views: 622

Re: Kernel Crash with GSM Modem AND I2C-0 Enabled

Check your power supply!
by rzusman
Sun Nov 19, 2017 1:19 pm
Forum: Compute Module
Topic: USB error in custom IO board
Replies: 10
Views: 1201

Re: USB error in custom IO board

Actually, I meant to write 10µF
by rzusman
Sat Nov 18, 2017 3:48 am
Forum: Compute Module
Topic: USB error in custom IO board
Replies: 10
Views: 1201

Re: USB error in custom IO board

OK. The D± traces should really be balanced and 90Ω, and that may be causing your problem, but I also notice that you don’t have any visible bypass and bulk decoupling capacitors next to the USB connector. They are important, especially for devices that have sudden high-current draw. Try soldering a...
by rzusman
Fri Nov 17, 2017 11:07 pm
Forum: Compute Module
Topic: USB error in custom IO board
Replies: 10
Views: 1201

Re: USB error in custom IO board

Post a detail of the layout from the CM socket to the USB connector, please.
by rzusman
Fri Nov 10, 2017 11:19 pm
Forum: Compute Module
Topic: Minimum Input high voltage (VIH) for 3,3V GPIO Supply
Replies: 5
Views: 879

Re: Minimum Input high voltage (VIH) for 3,3V GPIO Supply

Surprisingly, this value doesn’t seem to be published anywhere. But, these guys estimate it to be 2.1-2.3v: http://www.mosaic-industries.com/embedded-systems/microcontroller-projects/raspberry-pi/gpio-pin-electrical-specifications Still, you should not be pushing the spec. If you are using logic lev...
by rzusman
Thu Nov 09, 2017 1:47 am
Forum: Compute Module
Topic: Minimum Input high voltage (VIH) for 3,3V GPIO Supply
Replies: 5
Views: 879

Re: Minimum Input high voltage (VIH) for 3,3V GPIO Supply

Table 7 shows the 3V3 voltage range as ±5% or 3.135v - 3.465v
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: 663

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: 663

[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: 748

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: 781

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: 893

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: 893

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: 698

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: 581

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: 405

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: 454

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: 35410

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: 771

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: 326

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.

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