Beaglebone Black BOB Concept

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Thread: Beaglebone Black BOB Concept

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    Default Beaglebone Black BOB Concept

    Hi all,

    I've been playing around with an idea for a "modular" system for the BBB, if anyone plays with them. Basically it consists of cape and 1 or 2 "satellite" boards to provide a way of doing the 3.3v to 5v translation.


    Above is the cape to attach to the BBB


    Above is one of the satellite boards, this one has 8 Outputs for Step & Direction, 5 Inputs for Estop & Home\Limits, and 4 additional Outputs (yes the groupings are the same as a std Parallel Port. I call this the Output Board.


    Above is one of the satellite boards, this one has 8 Inputs say for a remote pendant with MPG, 5 Inputs for some buttons, and 4 additional Outputs (yes the groupings are the same as a std Parallel Port. I call this the Input Board.

    The satellite boards connect to the cape via a 26 way ribbon cable. The Inputs & Outputs are very basic, only a choice of pullup or pulldown resistors. If you want they could be connected to an existing BOB. All components are thru hole, as to aid in home construction.

    So far I have had an order of capes boards produced and output boards produced and tested. Hopefully the input board is due shortly. The thinking in doing it a modular way was to let others design their own boards, maybe satellite boards in other configurations. For those familiar with the BBB the groups of 8 outputs are connected to the PRU pins so the PRU can be used for step\dir. The Group of 8 inputs have 2 pins that can be used by the hardware encoder for a MPG.

    The cape also brings out the I2C signals and the analog inputs with the analog ground......unfortunately I didn't bring out the ref pin for the analog.

    The design files and some extra info is available at https://github.com/ozzyrob

    Cheers
    Rob

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    Default Re: Beaglebone Black BOB Concept

    Is this similar to the Necitec CNC cape for Beaglebone?



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    Default Re: Beaglebone Black BOB Concept

    Quote Originally Posted by Bravin Neff View Post
    Is this similar to the Necitec CNC cape for Beaglebone?
    As can be seen from the pictures this is a 3 board solution, all through hole components (for self assembly), once you have the cape installed you can design your own daughter boards, with your own input & output config. The inputs are NOT opto isolated.

    I guess it is similar to most other offerings, but it is open source and can be built by anyone with average soldering skills.

    The cape brings out the Analogue inputs on a 2x7 header, I2C bus on a 4x1 header, DGND, 3.3v, 5v_VDD, 5V_SYS and SYS_RST on a 2x5 header and a 2x1 header allows connection of a power off button.

    The 8 outputs, for step-dir on the Output board are connected to the PRU pins.

    The Input board has access to eQEP2A_in, eQEP2B_in & eQEP2_index for an encoder/MPG using the hal_arm335xQEP driver,
    pr1_pru0_pru_r31_15 & pr1_pru0_pru_r31_14 are also available (pr1_pru0_pru_r31_14 depends on eQEP2_index not being used)

    uart4_tx & uart4_rx are available as well.

    Obviously the above mentioned pins lose their use as GPIO when used as the functions listed.

    P8_26 is brought out to enable the input\output buffers, on the cape the BBB side is connected to the buffer side via a jumper, so that can allow you to put your own circuitry between the cape & buffers. Example you may want to have a watchdog signal on P8_26, route this to a watchdog circuit then connect the output of the watch dog circuit to the buffers. Or use P8_26 as an E-STOP input and one pole of the E-STOP switch could directly enable & disable the buffers.

    Each STEP-DIR pair is brought by a 4 way screw terminal with +5V and GND. The other inputs & outputs are brought out via a 3 way screw terminal with 5V & GND.

    The Outputs can either use a 74ls540 or 74ls541 depending if you want active hi or active lo outputs (source or sink). All IC's are socketed so if one goes bad it's just a simple job to replace them.

    All inputs & outputs groups can either have pullups or pulldowns configured.

    If you wanted to you could connect the daughter boards to a conventional parallel port breakout board, this would allow conversion from a PC setup to BBB setup without affecting your existing wiring.

    The daughter boards can either take their power from 5V_VDD or 5V_SYS. Or you may want to power the daughter boards from a separate 5v & 3.3v supply.

    The idea was to keep compatibility with a std pc setup (pin numbering & groupings), to allow for flexibility, to be open source and to allow a builder with soldering skills to construct the boards themselves. Even tho it has many options in reality it is very easy to use. One thing there is no input protection on the inputs but this can be addressed by the user, as simple control panel running at 5v may not need protection, but for home & limit switches it would be recommended.

    One other thing, the daughter boards have been sized to fit a 72mm din module for din rail mounting if that's not your thing 4 mounting holes are provided.

    I've also supplied a testing utility on my github site to allow testing the board prior to configuring Machinekit. Outputs can be manipulated and inputs can be monitored. On the books as well is a utility to test MPG\Pendant operation.


    Last edited by ozzyrob; 10-11-2017 at 06:38 PM.


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    Default Re: Beaglebone Black BOB Concept

    I like your design. Reminds me of the cards with ribbon cables inside big machines.

    I designed a similar cape for my miniature. Everything is on one PCB. I went with opto isolation, so all my machine signats are on a seperate PSU.

    It also has a LVDS circuit, so you can hook up any TFT flatscreen + touch. This part is not isolated.

    https://elinux.org/Optocape



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    Default Re: Beaglebone Black BOB Concept

    Nice design....my eyes aren't up to SMD soldering anymore.......Had no prob years ago just using a really hot iron and flux.........but not now...hence the thru hole parts.
    I thought about optos, but I decided if I need them I'll build an add on board, definitely when it's time to add limit switches (have a few designs in rough draft stage). The stepper drivers have optos, so I really didn't see the point in doubling up.

    I was thinking about adding a MCP23017 onto the I2c bus and figured I can use another set of daughter boards to buffer those signals.

    At the moment I've managed to compile hidcomp on the BBB and am experimenting with a USB hid based control panel. My mpg pendant will make use of the machinekit PRU encoders.



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