2008 - Page 5 of 5 - Micromouse Online

LS7366 quadrature counter

Post author:Peter Harrison
Post published:February 21, 2008
Post category:Micromouse
Post comments:20 Comments

The LS7366 is a 32 bit counter with a direct interface for quadrature signals from incremental encoders. There is also an index channel for marker functions. The interface to the microcontroller is SPI mode 0 making it relatively easy to drive with a variety of common controllers. Decimus has one of these on each motor channel connected to the encoders on the back of the Faulhaber 2224 coreless motors. There is very little information about these chips available except the data sheet. This is how they are used on Decimus. (more…)

SPI data transfers

Post author:Peter Harrison
Post published:February 21, 2008
Post category:Hardware
Post comments:2 Comments

I use SPI on my micromouse both to talk to the Nokia graphical LCD and to talk to the LS7366 quadrature encoders. A large number of devices can be connected to the SPI data lines, MOSI and MISO. Each device needs its own select line. This all appear very simple and friendly. There is, however a potential problem due to the flexibility of the SPI configuration.

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Battery voltage monitor

Post author:Peter Harrison
Post published:February 18, 2008
Post category:Micromouse
Post comments:0 Comments

Decimus has one of the ADC inputs dedicated to monitoring the battery voltage. The batteries used in this micromouse are Lithium Polymer cells and it is particularly important that they are not allowed to discharge too far. Since the full battery voltage is about 7.4 Volts, this gets divided by four in a simple resistive divider before being sampled by the ADC.

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LCD testing for Decimus

Post author:Peter Harrison
Post published:February 18, 2008
Post category:Micromouse
Post comments:5 Comments

Having installed the LCD, it was time to get the code working for it. First I realised that it may not have been so clever to put the LCD on the same SPI port as the encoders. This will mean that I have to take care that the encoders are not being read when the LCD is active. Since the encoders are sampled every interrupt, it means turning them off while writing to the screen. That, in turn, means not writing to the screen while moving, or holding position. I may end up having to patch the board to put the LCD on the other SPI port. In fact, I wish I had done that in the first place as it would just share lines with the UART and I could easily switch between the UART and the SPI for writing debugging messages. Ah well, live and learn. (more…)

LCD screen for Decimus

Post author:Peter Harrison
Post published:February 10, 2008
Post category:Micromouse
Post comments:0 Comments

Probably the last part to be added to Decimus will be the Nokia 3410 LCD screen. Nearly all of my mice have these either permanently fitted or attached by a simple socket so they can be removed. With a resolution of 96x64 pixels, this screen is an ideal debugging aid.…

Wheel assemblies for Decimus 2

Post author:Peter Harrison
Post published:January 10, 2008
Post category:Hardware
Post comments:4 Comments

The wheels have given me so much trouble that it all has to be downhill from here. This is how they are put together.Good wheels are essential in a micromouse. We want something that is robust, reliable and capable of precision, repeatable movement. There should be no wobbling and shaking and their relationship to the body of the mouse must be constant, or at least predictable. Clearly, the grip of the tyre is essential for high performance. The wheel in a simple mouse will probably need to carry the final stage reduction gear. (more…)