Note:

The BBB has tons of possibilities. But the GPIO pins must be chosen with care. I am running for example Debian on the intern eMMC. That means that we can not use on P8, 3-6 and 20-25, as GPIO. An other example is the HDMI. By disabling HDMI there will become 20 pins free (P8, 27-46). So in my case I lost already 30 pins for GPIO because of the use of eMMC and HDMI.

SPI can only be used without HDMI. 

In Proview:

Digital Output :

Tried with 3 LEDs and 470 ohm resistors, works..

Analog Input :

7 Multiplexed 1.8V analog inputs going to a 100KHz 12-bit ADC (the eighth channel is used by the system). Because of the 1.8 Volt limit,  11-bit for the linux driver (0-2047)

Tried AIN1 with LDR and 10k Ohm resistor. Setup as voltage divider. I used VDD_ADC1 pin (P9, pin 32), steady 1.8 Volt. Converted between 0-1.8 Volt.

In Proview I read the value in from /sys/device/ocp.2/helper.14/AIN1 by using an onewire-AiDevice in the node configuration. Using Ai's in Proview with the BBB uses lots of CPU resources using a PLC scan time from 100 ms. A second plcprocess in node with for example a PLC scan time of 1 sec for slow data sampling is a way to press the CPU resources down.

"Works"......

PWM:

I am running kernel: 3.8.13-bone20

Pretty confusing, lots of people have problems with PWM.

eCAB driver, eHRPWM, SYSFS interface, Device Tree.... Lots of changes the changes in Linux > 3.8......

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I have build a new kernel, based on 3.8.13.

PWM, period= 500 microseconds (2 kHz), which is default, with a variable duty.

used: /sys/devices/ocp.2/pwm_test_P8_13.15/ as test and is working.

At the moment I have 6 PWM's working with Proview; P8_13, P8_19, P9_14, P9_16, P9_21 and P9_22. The BBB has 8 PWM's so I still miss 2. I have set the polarity to "0" of the PWM's.

The 1A/B and 2A/B PWM outputs pairs are coupled and synchronized, they can only have the same period . If we use a pair the period of the duty starts on the same time of the 2 outputs.

OK. Sysfs is great if you don't need speed. But one thing is for sure I want to move to /dev/mem.  By mapping the GPIO to /dev/mem our dreams can become true. Please use the guest book for ideas.....

Next step is to find a mosfet with a threshold voltage < 1.8 Volt.....

18-2-2016

Blow the dust of the BBB and started to read about the PRU possibilities of the BBB. GPIO by using the sysfs is sometimes too slow...

A programmable real-time unit (PRU) is a fast (200-MHz, 32-bit) processor with single-cycle I/O access to a number of the pins and full access to the internal memory and peripherals on the AM3358 processor on the BBB.

Started with 7 analog inputs (AIN0-AIN6).... Looks promising....