Arduino header analog pins

jsmarion

OK, trying one more time to ask for a little help.

I'v spent about a day messing with the arduino analog pins and they don't actually seem to be connected to the BBB ADC pins at all, as it says in the manual or the specs. Can someone please comment on how to access the arduino ADC pins from the BBB when using the LogiBONE?

Thanks in advance. 

mjones

Hi @jsmarion

The Arduino analog pins are just connected to a voltage divider resistor footprints on the PCB.  This allows you the get the shield analog signals to a level compatible with the BBB (<1.8V I believe).  You will need to "jumper" the arduino analog pins to compatible BBB ADC pins in order use the BBB ADCs.  There is an extra header (unpopulated) that you can use to "jumper" the arduino pins if you are using an arduino shield at the same time.  

See attached image to see how it is wired.

jsmarion

Thanks very much for the answer. 

May I respectfully suggest that someone update the information on the site (i.e. the schematic and the description), as both seem to suggest that these pins are connected to the P9 connector (pins 33, 36-40). 

The schematic I'm refering to: https://github.com/fpga-logi/logi-boards/blob/master/fpga-boards/logi-bone/PRJ-DOC/sch/sch-logi-bone-r1_5_1.PDF

And the description, where it says "The LOGI Bone implements 6 ADC input pins that interface directly to the BBB ADC pins. " : http://valentfx.com/wiki/index.php?title=Logi-Bone_User_Guide#ADC_Functionality_and_Wiring

mjones

Sorry for the confusion.  I was wrong on the last post.  The pins are indeed connected to the P9 pins.  Attached are the electrical connections and schematic which shows the p9 pins that are connected to.

Depending on the board version you are using the resistors may not be populated so to no conflict with alternative functionality and to leave the user to be able to use an appropriate divider needed to get desired voltage levels for the adc.  If you want to directly connect to the p9 pins without a voltage divider you can use only populate or "short" resistors R38,39,40,32,33,34 (high side resistors).  

Sorry for the confusion.

jsmarion

Ah... got it... it's the missing resistors. 

How the heck am I supposed to solder those tiny things on there... :-)

mjones

Yeah,  kinda small as we didn't have a lot of room to work with.  If you don't need to voltage divide the signals you could just use the extra header to solder/jumper the signals directly.  

jsmarion

Gotcha. Thanks kindly for your help.