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by maxchess42
Fri Dec 02, 2016 7:23 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: I2C problems when adding more than 3 devices
Replies: 25
Views: 3721

Re: I2C problems when adding more than 3 devices

massi, you say you just need to write a 0b11111111 to the multiplexer to have all 8 channels enabled Under the device tree method, I would get 8 new buses and just use the right one per device. with a statement like: bus = smbus.SMBus(3) In your method with all channels open how do I direct a call t...
by maxchess42
Thu Nov 10, 2016 8:22 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: I2C problems when adding more than 3 devices
Replies: 25
Views: 3721

Re: I2C problems when adding more than 3 devices

I just want to make sure I understand what to do, at the risk of exposing my ignorance. So I connect the Mux and run either 3.3v or 5v to my devices as appropriate and then I Add "dtoverlay=i2c-mux,pca9548" to /boot/config.txt and you say that the 8 ports are presented as 8 independent I2C buses by ...
by maxchess42
Thu Nov 10, 2016 1:11 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: I2C problems when adding more than 3 devices
Replies: 25
Views: 3721

Re: I2C problems when adding more than 3 devices

OK thanks, I will do as you suggest and see what happens, however the impression I am getting is that trying to run multiple 5v devices from the PI is unlikely to work and that running 4 or more I2c devices at 3.3v requires careful monitoring and planning. I will try to get this working as a learnin...
by maxchess42
Wed Nov 09, 2016 4:41 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: I2C problems when adding more than 3 devices
Replies: 25
Views: 3721

Re: I2C problems when adding more than 3 devices

Ok I will try some of these ideas. Wnen you say : "add another 3k3 or 2k7 resistor in parallel to make an effective pull up of around the 1k0 mark." where do these resistors go. Is there one each from the power line and SCL/SDA ? Also I wonder whether this level shifter might help: https://www.adafr...
by maxchess42
Wed Nov 09, 2016 1:23 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: I2C problems when adding more than 3 devices
Replies: 25
Views: 3721

Re: I2C problems when adding more than 3 devices

The 5 devices I am trying to connect are: 4 x MCP23017 1 x Adafruit HT16K33 16×8 LED Matrix Driver. The MCP23017. The MCP23017 is a packaged IC, it does have internal pull ups that can be set, but that's done later by program. I don't think its possible to remove the resistors. I have tried the I2C ...
by maxchess42
Wed Nov 09, 2016 11:58 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: I2C problems when adding more than 3 devices
Replies: 25
Views: 3721

Re: I2C problems when adding more than 3 devices

Ok, so I have added the capacitors, but not yet the resistors and can still see a maximum of only three devices out of 5. I then tried it wired up to an Arduino Nano and I can see all devices and they all seem to work. Absolutely identical I just moved the SCL, SDA, GND & 5v from one to the other. I...
by maxchess42
Tue Nov 08, 2016 9:41 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: I2C problems when adding more than 3 devices
Replies: 25
Views: 3721

Re: I2C problems when adding more than 3 devices

Also don't have 8.2k resistor to hand, is 10k alright?
by maxchess42
Tue Nov 08, 2016 9:29 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: I2C problems when adding more than 3 devices
Replies: 25
Views: 3721

Re: I2C problems when adding more than 3 devices

I will try the capacitors. You diagram shows a non polarized 0.1 uf and a polarized 100 uf. I assume the first one is a ceramic style one? Is that correct?
by maxchess42
Tue Nov 08, 2016 3:17 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: I2C problems when adding more than 3 devices
Replies: 25
Views: 3721

Re: I2C problems when adding more than 3 devices

Hi,
Pin 18, Reset and Pin 9 VDD connected to “+”
Also all devices show correct address when queried individually or in group of 2 or 3. Its just when a 4th is added it goes crazy.
Photo of basic connections attached.
It seems like some sort of noise or interference
Max
by maxchess42
Tue Nov 08, 2016 12:58 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: I2C problems when adding more than 3 devices
Replies: 25
Views: 3721

I2C problems when adding more than 3 devices

Hi, I am building a chessboard ( http://chess.fortherapy.co.uk/home/a-wooden-chess-computer/design-ideas-for-easy-to-build-beaglebone-black-chess-computer/ ) using I2c and when I add more than 3 devices the I2c behaviour becomes erratic. I have 4 MCP23017's each controling 16 reed switches , adresse...
by maxchess42
Tue Oct 13, 2015 10:06 pm
Forum: Automation, sensing and robotics
Topic: Tracking movement of game pieces on a board
Replies: 14
Views: 5039

Re: Tracking movement of game pieces on a board

See http://www.chess.fortherapy.co.uk for a comprehensive description of how to build a chessboard with piece detection using reed switches. When bought in bulk on ebay reed switches are cheap and work reliably.
by maxchess42
Thu May 29, 2014 2:39 pm
Forum: General discussion
Topic: Text to speech through a USB sound card
Replies: 8
Views: 2976

Re: Text to speech through a USB sound card

Ignore my last post, just re-read the previous post and the bit about making the USB as device 0. Works great now with all the stuff as per the original post.
by maxchess42
Thu May 29, 2014 2:26 pm
Forum: General discussion
Topic: Text to speech through a USB sound card
Replies: 8
Views: 2976

Re: Text to speech through a USB sound card

I had a similar problem with a USB card. At first neither my USB attached mic or speakers worked. Then I checked what devices I had using $ aplay –l The command the shows the RPI default card as 0 and the USB device as 1 So I put the following in my config file: pcm.!default { type hw card 1 } ctl.!...
by maxchess42
Thu May 23, 2013 1:18 pm
Forum: Gaming
Topic: Raspberry Pi dedicated chess computer/board
Replies: 26
Views: 14257

Re: Raspberry Pi dedicated chess computer/board

This is a really neat project, however not everyone can afford a DGT board. I was a able to build a fully working chess computer that recognises piece positions using reed switches and signals its move using a LED on each square for about £80, plus a bit of hard coding and amateur woodwork. It runs ...

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