can I use any of the GPIO of the Beaglebone, for analog reading?

Asked by 5 months ago
Was wondering how many of the GPIO I can use for analog reading. I have many sensors that output only in analog; so I was wondering if that may work, since the BBB has only 7 Analog IO, while the rest are all digital. If I can't plug more than 7 analog IO, how could I plug in more? Thanks.

Your Answer

Name:
Reply:

All Answers

Answer by 5 months ago
Maybe you need more ADC chips . I dont know how to use gpio as as analog reading , As I understand , GPIO only get 2 level input 1 or 0 , and if your analog signal over 2 levels ,how to measure ? Another idea is use TDM switcher , maybe you can find some chip can do switch several ADC input and 1 or more digital output . I dont know if there is this kind of chip ,maybe 2014-02-13 9:00 GMT+08:00 Karl Longen 2frikkincraze2 [ at ] gmail.com:
Answer by 5 months ago
Quoted message by Liyaoshi 5 months ago
Maybe you need more ADC chips . I dont know how to use gpio as as analog reading , As I understand , GPIO only get 2 level input 1 or 0 , and if your analog signal over 2 levels ,how to measure ? Another idea is use TDM switcher , maybe you can find some chip can do switch several ADC input and 1 or more digital output . I dont know if there is this kind of chip ,maybe 2014-02-13 9:00 GMT+08:00 Karl Longen 2frikkincraze2 [ at ] gmail.com:
The system is capable of reading the ADC inputs rapidly in round-robin fashion. It depends on having kernel support for this. The changes went into the mainline kernel last fall: http://beagleboard-gsoc13.blogspot.com/
Answer by 5 months ago
Quoted message by Liyaoshi 5 months ago
Maybe you need more ADC chips . I dont know how to use gpio as as analog reading , As I understand , GPIO only get 2 level input 1 or 0 , and if your analog signal over 2 levels ,how to measure ? Another idea is use TDM switcher , maybe you can find some chip can do switch several ADC input and 1 or more digital output . I dont know if there is this kind of chip ,maybe 2014-02-13 9:00 GMT+08:00 Karl Longen 2frikkincraze2 [ at ] gmail.com:
This patch is for ADC touch screen , generally resistive touch screen will have 4 lines for ADC X+ X- Y+ Y- so , this will cost 2 ADC for my understand , this round robin is just between this 2 ADC , instead of two sensors in one ADC converter. From top thread , if you want to use over 10 sensors for ADC , you need external ADC chip . and do some communication work with am3358 If you want to have some flexable and no much than 10 sensors , what about add a stm32 ? 2014-02-14 5:01 GMT+08:00 craig.markwardt [ at ] gmail.com:
Answer by 5 months ago
Quoted message by Liyaoshi 5 months ago
This patch is for ADC touch screen , generally resistive touch screen will have 4 lines for ADC X+ X- Y+ Y- so , this will cost 2 ADC for my understand , this round robin is just between this 2 ADC , instead of two sensors in one ADC converter. From top thread , if you want to use over 10 sensors for ADC , you need external ADC chip . and do some communication work with am3358 If you want to have some flexable and no much than 10 sensors , what about add a stm32 ? 2014-02-14 5:01 GMT+08:00 craig.markwardt [ at ] gmail.com:
Thanks for the suggestions; The issue is that these sensor may need to communicate with the board at the same time; imagine a sort of mocap device for a quadruped: if they walk, they are in fact using all 4 legs at the same time, so I need a way to capture these values at the same time. From what I understand, if I use an ADC, I am forced to tell it to switch to a specific input, so it works more like a radio selector (multiple station, but you can get only one at time), than a electric strip (many plugs can take electricity independently at the same time). The solution that you mentioned (the one with the device that send all the data at once), seems functional to my case. I don't need instantaneous reactivity by the device, since it is more used to capture data on movements, convert it to something that the main computer can digest (done on the BBB), and then sent to the computer, that will grab the data and apply it to a mesh. Each of these steps will take time, so I am aiming at something usable with a small lag; that's why Analog seem the quickest way to get the data out. I am basically clueless about what could I potentially buy, to achieve what I want; and can't really find any reference online...if there is one is either well hidden or people don't like to talk about it.