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Junior Member
 
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Last Login: Saturday, April 24, 2010 11:05 AM
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| Hello, I am looking at using your serializer board to control two motors for differential drive on a robot, with the 7.2DC motors and quad encoders you supply. However, I am also looking to not use your PID control algorithms and instead implement an IMU and develope a seperate algorythm. The micro controller I will be using is a Gumstix with PWM out, I2c, and 1.8V logic levels. My questions are as follows: 1) Can the serializer board be controlled with I2C alone, without your USB or serial expansion boards? 2) Can the encoder data be outputed across I2C and what level of bandwidth would that data consume if being used in an outside PID algorythm? 3) Does the serializer accept 1.8V logic levels or adjustible logic levels? Thank you for your time!
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Junior Member
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| Also one more question: 4) What is the output voltage that is passed to the motors, is it regulated or does the serializer pass the input voltage straight to the motors without step down?
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Supreme Being
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Hi, I believe I can address some of your query.
1) The Serializer is controlled by serial only. It can be of several
different interfaces, usb, XBee, Bluetooth, TTL.
Its I2c is a far side interface meaning the Serializer can communicate
to other I2C devices. This does not allow control of the Serializer via
I2c.
2) the Encoders are read via the serial commands over serial.
3) 1.8, 3.3 vDc logic will require level convertors except on the
analog inputs.
4) The present Serializer has a 12vDC top level input. This voltage
will be passed to the motors as PWM. With 7.2vDC motors and
12vDC input your motors might run hot at greater than 75% speed.
note: I understand there is a newer version of the Serializer soon to be
released that has somewhat different specs. You might enquire.
Someone from Roboticsconnection please correct me if I am wrong.
enjoy,
Don Lewis
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Supreme Being
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Don is right on with his answers...a few additional specs...- The Serializer serves as an I2C Master, and it can communicate w/ any other i2c slave device.
- Does your gumstix have a free serial port? If so, you would need some kind of level converter to go from 1.8 to 5.0v, and you could connect directly to the TTL serial pins on the board (and wouldn't need a module). I don't know of such a converter readily available.
- The PID algorithms are built into the firmware, so you don't have to bother querying encoder ticks to control speed and distance...it's all handled for you already. You can query the ticks to see how far your bot has traveled, or you can simple tell the SErializer to drive the bot a specific distance (digo cmd) and it'll handle the rest for you.
Also, this weekend we are launching the new Serializer v3.0. We've dropped the price (by reducing manufacturing costs) to $99.95, added a lot of new hardware features, have updated the firmware (and added new functionality), and will be open sourcing the .NET lib. I'll post more detailed info about it this weekend.  Best Regards!
Jason Summerour
President,
Summerour Robotics Corporation
www.roboticsconnection.com
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Junior Member
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| So just to clarify, the serializer only responds to commands in TTL RS232 and cannot be controlled using I2C? If that is the case, does the USB module you supply act as an RS232 adaptor? Also the question regarding the PID control is regards to using an external PID algorithm that accepts an input from an IMU. This is for a senior project, and designing my own PID algorithm would be advantageous when using a much more accurate IMU input and data blending with the encoder data. Therefore, is there any way on the new V3.0 board to output the encoder data or atleast access the PID algorithm and modify the inputs, such as adding a IMU input?
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Supreme Being
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Hi,
I see Jason has made available the new Serializer WL 3.0 information
on the roboticsconnection sales site. Looking over the new manual I see
that only encoder A inputs can be retrieved for use and that encoder B
inputs are reserved for PID.
I think you might use your own code to read the enc-A inputs for motion
or speed and use the MOGO with your code for motor control.
I need more clarity myself..
later,
Don Lewis
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Supreme Being
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| The Serializer repsonds to serial commands. You send it serial command over either the RS-232 module, USB module, XBee module, or TTL port (for direct connection to microcontroller serial port). To the host computer talking to the Serializer, the RS-232, USB, and XBee modules all look like a serial port. So, it's as easy as opening up a Serial Port, and sending/receiving commands. We designed the firmware to handle the PID algorithms for you and handle watching all of the encoder ticks, etc. This allows you to focus on other stuff. If you're attempting to implement your own PID algorithm (which is a cool project by the way), then you woudl be better suited doing that directly in another microcontroller board, where you can upload your own code, and have direct access to variables in memory holding encoder tick counts. You won't get accurate results if you have to send serial commands down to get the encoder ticks that have passed by. Hope that helps!
Jason Summerour
President,
Summerour Robotics Corporation
www.roboticsconnection.com
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Junior Member
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| Thanks for your response. I have a little more to ask. When you say TTL port are you refering to SPI or I2C or some other physical serial protocol? Also can this controller act as a serial host/gateway? I'm thinking that the easiest way to connect this controller to my microprocessor board will be using USB. I plan on using some sensors that have serial buses (SPI an I2C) can I send commands over the USB link from my microprocessor board, through the controller, and to these sensors as well as receive data from them over the same link?
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Junior Member
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| I forgot to mention that I will probably wind up using the onboard PID algorithm. I'm asking these further questions because I am looking at all of my I/O options for my projects various subsystems to make sure they will all interoperate as I need.
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Supreme Being
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