raspberrypi expansion module

Request new hardware or ideas for the controller

Posts: 11
Joined: Tue May 14, 2013 3:07 pm
PostPosted: Mon Aug 26, 2013 10:07 pm
I am able to upload sketch to an UNO over the RPi's GUIO UART. I am also able to send and receive serial information between the two over the same connection.

It would seam to me if I had the webpage that is running on the RA Wifi card I could setup up on the RPi's web server and have some PHP or Python to do the translating between the to. If this is the case then the RPi could be used as a Wifi card replacement with out loose of portal or phone use functions.

To program the UNO I have to hold down the reset till avrdude start to upload. This will not work for remote uploads to the RA. I have learned that the chip is reset before upload data generally by a DTR pin on arduinos. Is this what the CTR pin on the RA is for? If so we should be able to adapt one of the RPi GPIO pins to do the job, like is is shown herehttp://www.deanmao.com/2012/08/12/fixing-the-dtr-pin/ Would I need a logic level shifter for this pin too?

With this done one would be able to upload sketch from anywhere. The trouble I see with this is that the RA likes to be reset after a sketch. Best idea I got for this is to have the PRi controls a relay that sits on the communication cable. We could have a block with the relay sit between 2 communication cables, and use it to power the RPi. I think this solution could be used to do the programming reset too.

I have been doing most of my base work on an UNO because my RA is running my reef...

Please tell me your thoughts and what I am missing.
Last edited by Atari on Fri Oct 10, 2014 8:40 pm, edited 1 time in total.
User avatar
Posts: 5348
Joined: Fri Jul 20, 2012 9:42 am
PostPosted: Tue Aug 27, 2013 4:38 am
The web page is not in the wifi card...the web server and stuff is all on the RA. If you setup a http proxy that will pass the get requests over serial you will get the responses back over the serial.

Posts: 12225
Joined: Fri Mar 18, 2011 6:47 pm
PostPosted: Tue Aug 27, 2013 7:46 am
If you plug the USB-TTL cable to the PI, you can upload codes to RA without any modifications :)
All you need is a TCP to UART proxy to go straight to the RA webserver.
Or, you can create your own webpages and simply issue commands through the serial port. Either way would work :)
Are you good with python?

Posts: 12
Joined: Sat Jun 29, 2013 3:54 am
PostPosted: Fri Jan 10, 2014 11:20 pm

any news?


Posts: 1
Joined: Tue Jan 28, 2014 10:50 pm
PostPosted: Fri Jan 31, 2014 8:54 am
When the Raspberry Pi came out I was really excited too but found it lacking in basic I/O capabilities (PWM) for a long time. Meanwhile at my work we discovered the BeagleBone (particularly the BeagleBone Black) and I have found them to be great. Either way a HTTP relay should be like twenty lines of code in Python on either so I will give it a shot with my gear (while doing my thesis....so bear with me :p )

Posts: 28
Joined: Mon Jan 20, 2014 7:41 pm
PostPosted: Wed Feb 26, 2014 4:56 pm
The tcp->UART bridge is too easy from Linux using socat I do this all the time for network serial ports on servers as far as the portal is concerned I just need to figure out what exactly gets sent to the portal and you can easily write a chrond script that will read the necessary data from the RA and push it to the portal going to dig my beaglebone black out tonight

Posts: 28
Joined: Mon Jan 20, 2014 7:41 pm
PostPosted: Wed Feb 26, 2014 9:33 pm
just got home and was doing some more thinking on this and on my beaglebone it is even more simple because i have 4 uart ports so i simply connect the wifi connector to one ttl port and RA to the second ttl port and bridge the two ttl ports using socat and then when i need to upload code or directly interface with the RA i can unbridge the connection which will cause ra to reset and receive commands

not sure how many ttl ports a PI has but you could always use usb to ttl cables and a usb hub

can i get the ra pinouts and the wifi connector pinouts going to breadboard this up tomorrow

Posts: 28
Joined: Mon Jan 20, 2014 7:41 pm
PostPosted: Thu Feb 27, 2014 6:36 am
3.3 to 5v logic shift can be handled using a voltage divider on the arduino tx pin

Posts: 12225
Joined: Fri Mar 18, 2011 6:47 pm
PostPosted: Thu Feb 27, 2014 10:11 am
I use the usb-ttl cable connected directly into the PI and works fine.
I'm able to upload codes and everything.

Posts: 28
Joined: Mon Jan 20, 2014 7:41 pm
PostPosted: Thu Feb 27, 2014 3:49 pm
Yes because the USB TTL cable is 5v tolerant but my beaglebone USB port is In Use for my WiFi adapter

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