With the AA80E we are struggling to get enough outputs to drive all the solenoids and either the speedometer drive or the gear readout is looking like a casualty so I would like to make an observation and see if it goes anywhere.
You can get 8 separate indications from 3 binary digits.
000 1
001 2
010 3
011 4
100 5
101 6
110 7
111 8
Of course most of us aren't fluent in binary and the typical 7 segment driver is not set up to convert these numbers to decimal 1 through 8 since it is a shift of one decimal position by making 000 = 1. But that would free up a driver. Can anyone think of a relatively simple way that we could make this work? (Power to the display could be cut in N/P to blank the display. Maybe it could flash in R.)
Jim
Gear position display
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Bernard Fife
- Posts: 1696
- Joined: Fri Apr 04, 2008 1:28 pm
Re: Gear position display
Jim,
The 7-segment info is here: http://www.msgpio.com/manuals/mshift/7segment.html As you suggest, for an 8-speed trans, you would likely want to show 1 to 8, requiring 4 outputs in the 7-segment's native format (the forth output switches low for numeral "8", because 0 is the first number). But I suppose you could use LED1-LED3 for 1-7, and then use LED4 as a solenoid driver (with the appropriate hardware, of course). If there was an solenoid output that was high only in 8th, then this could be piggybacked on to form an input for the 7-segmnent driver to display an "8" (or there may be other outputs that happen to correspond to the required inputs).
However, for more outputs here are a couple of other possibilities:
- a second GPIO board could run auxiliary code controlled by the main board to switch another set of outputs (up to about 20 of them). The auxiliary code hasn't been written, but if there is sufficient demand for it, I could whip it up fairly quickly, I suspect. This is the beauty of CAN - the ability to extend boards by chaining them together.
- an SPI driven chip could be used to drive additional outputs. This would re-purpose the LED outputs as SPI channels, but would allow many more PWM and other outputs. For example, SPI could be used to drive a 7-segment driver as well as something like this: http://www.freescale.com/webapp/sps/sit ... de=MC33800. If there was sufficient demand, we would produce boards ready to run for this. V4.1xx code has much of the SPI infrastructure in place, but it has not been tested properly.
Lance.
The 7-segment info is here: http://www.msgpio.com/manuals/mshift/7segment.html As you suggest, for an 8-speed trans, you would likely want to show 1 to 8, requiring 4 outputs in the 7-segment's native format (the forth output switches low for numeral "8", because 0 is the first number). But I suppose you could use LED1-LED3 for 1-7, and then use LED4 as a solenoid driver (with the appropriate hardware, of course). If there was an solenoid output that was high only in 8th, then this could be piggybacked on to form an input for the 7-segmnent driver to display an "8" (or there may be other outputs that happen to correspond to the required inputs).
However, for more outputs here are a couple of other possibilities:
- a second GPIO board could run auxiliary code controlled by the main board to switch another set of outputs (up to about 20 of them). The auxiliary code hasn't been written, but if there is sufficient demand for it, I could whip it up fairly quickly, I suspect. This is the beauty of CAN - the ability to extend boards by chaining them together.
- an SPI driven chip could be used to drive additional outputs. This would re-purpose the LED outputs as SPI channels, but would allow many more PWM and other outputs. For example, SPI could be used to drive a 7-segment driver as well as something like this: http://www.freescale.com/webapp/sps/sit ... de=MC33800. If there was sufficient demand, we would produce boards ready to run for this. V4.1xx code has much of the SPI infrastructure in place, but it has not been tested properly.
Lance.
"Never wrestle with pigs. You both get dirty and the pig likes it." - George Bernard Shaw