AA80E 8-speed

A forum for discussing applications and implementations of the MegaShift transmission controller code for the GPIO from B&G. This can control up to 8-speeds and 6 shift solenoids (plus a 16x9 table for controlling a PWM line pressure valve). It has manual and fully automatic modes (16x9 load x speed table), with under and over rev-limit protection, and full data logging of all inputs and outputs (among many other abilities). A TransStim to test your completed board is also available.
Jim Blackwood
Posts: 222
Joined: Tue Dec 07, 2010 9:52 am

Re: AA80E 8-speed

Post by Jim Blackwood »

Here's a thought, how about if we just use two LEDs for gear position indicators. Say a yellow one for 1st gear and a green one for 8th. Other than that does it really matter which gear it's in? Doesn't seem like it to me. I'd rather be looking at the tach than a gear position indicator. Back in '74 I bought a bike with a segmented gear display which was handy but I discovered I only used it to find neutral when I stopped or to see if I was in top gear. Don't even need to do that here but if it is wanted I don't know why more than that is important. Maybe just one for 8th. Chances are even that one's not needed, but I can see where it might come in handy.

JB
Jim Blackwood
Posts: 222
Joined: Tue Dec 07, 2010 9:52 am

Re: AA80E 8-speed

Post by Jim Blackwood »

Another thought. Using two LED's (say yellow and green for instance) 0=1st, Y=2, G=3, YG=4, Y=5, G=6, YG=7, 0=8. No bothersome lights in cruise or 1st. Or some other scheme. Regardless it tells you with some certainty which gear it's in with only two outputs. I think that gives us enough outputs doesn't it?

JB
BupapaddyCoff

Re: AA80E 8-speed

Post by BupapaddyCoff »

I had misspoken earlier when I suggested that the solenoid drivers could double as alternative outputs for LEDs. What I meant to day is that they could be used to drive a seven-segment display.
Jim Blackwood
Posts: 222
Joined: Tue Dec 07, 2010 9:52 am

Re: AA80E 8-speed

Post by Jim Blackwood »

You might do that, but the logic might be a little contorted and you might not be able to simply use a 7 segment display driver without some logic circuits to untangle the various solenoid outputs. It would work though, I just looked at the chart for solenoids 1 through 5 and the logic sequence would be straightforward enough. You wouldn't get by with a straight connection but a few extra gates and you'd be there I think. Make a nice option if we need yet more outputs for some reason. I have a few 7 segment displays and driver chips, Maybe I'll play with that a bit.

JB
Jim Blackwood
Posts: 222
Joined: Tue Dec 07, 2010 9:52 am

Re: AA80E 8-speed

Post by Jim Blackwood »

I have finished the 1st draft comprehensive system spread sheet and attached it here. It is color coded for inputs, outputs, CAN, grounds and power connections. I have added Lance's recommendations on the GPIO/Megashift section and added notes where I was reasonably certain they were accurate. My next step would be to make recommendations on how to complete the connections but others more qualified and knowledgeable about what will work and what will not may want to step in here. I realize we're setting the pattern for future applications and I don't want to take that down the wrong path due to my ignorance. The need for a stand-alone version will undoubtedly influence that direction.

I'm not really expecting a lot of help on the sections other than MegaShift from this forum, just including the rest to make it easier to see how it all fits together. There may be some redundancy that can be trimmed.

Aside from that, I think it's a pretty good start and may prove helpful to others. Still seems to be a good bit of work to go and there may be better ways to do some things than what I come up with.

On the shifter, The stock AA80 gear select input shaft has the usual PRND detented positions and it will move beyond the D position one more undetented increment. I do not know if this has a function or not. If it does, it could only be for downshift. More likely it is there simply to allow the shifter to be moved in the +- gate. I do not yet have a shifter so I cannot confirm this yet. The switch assembly is mounted to the transmission housing and has 2 large and 7 small connection pins. Clearly this is not likely to be digitally encoded, but I will look into it further to be sure. I still do not have the wiring harness. I would suspect the two large pins are for the backup lights, leaving the 7 remaining ones for position but that is more than are needed obviously. I have put out a quote request for the harness and hope to resolve this question within a couple weeks. I will look up the switch on the wiring diagram for the transmission and see what I can find there, and attempt to label the solenoid connections more more explicitly.

Just keep in mind this is a draft. It's got a ways to go yet.

JB
Jim Blackwood
Posts: 222
Joined: Tue Dec 07, 2010 9:52 am

Re: AA80E 8-speed

Post by Jim Blackwood »

I have added the transmission control connector and the gear selector switch connector and the pin assignments. This should make things a little easier.

JB

Edit: The gear selector switch is a simple mechanical switch. For the PRND positions it tales power from the #2 terminal. The interlock contacts are isolated.
Jim Blackwood
Posts: 222
Joined: Tue Dec 07, 2010 9:52 am

Re: AA80E 8-speed

Post by Jim Blackwood »

Should have waited and uploaded this all at the same time.

Anyway, I have the EA45/EA47 pin assignments in the Megashift section now where the assignments are clear and have noted the Ampseal pin numbers in the EA45/47 sections as well. I have red highlighting in the "D" column next to the unknown solenoid assignments in both sections.

Lance, I was unsure about the assignments for the solenoids so I have waited to enter the pin numbers. I know you had fairly specific assignments in mind. If you wouldn't mind thinking back to how you wanted to do that I'll be glad to update the notes and look to see what else is needed. You'll notice I have 2 more solenoids than I have spots for, that's about as close as I could get to where I think you were going with it.

I have more flexibility than someone with a standalone application. I will be looking at the possibility of a GPS speedo and I will be able to use CAN for the inputs from MS so whatever works for standalone will probably be fine for mine. I will also be just fine with a 3 LED display that goes 1,2,3, blank,1,2,3,blank for instance for the 8 gears. I should have no problem telling whether I'm in the 1st 4 or the 2nd 4 gears and blanking the display in top gear is a good idea.

JB
Bernard Fife
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Joined: Fri Apr 04, 2008 1:28 pm

Re: AA80E 8-speed

Post by Bernard Fife »

Jim,

For the outputs for the solenoids, Outputs 1, 2 and 4 have bit banged pulse width modulation. Output 3 has a timer channel, so the PWM is quite a bit more accurate. Output 3 also is the only one of the 4 outputs that can be set to a different value while shifting than it is in either the ON or OFF states (useful for some transmissions, I don't know about yours though).

Output 1 is on the VB3 circuit (Amp pin 23), and this is set up to handle a fair bit of current in a TO-220 transistor placed on the heat sink.

Output 2 is on the VB4 circuit (Amp pin 35), and this is set up to handle a fair bit of current in a TO-220 transistor placed on the heat sink.

Output 3 is on the PWM1 circuit (Amp pin 34), and this is set up to handle a fair bit of current in a TO-220 transistor placed on the heat sink. It is the only one of the outputs to have a 'shift state' PWM as well as an ON and an OFF PWM.

Output 4 is on the VB2 circuit (Amp pin 12); it is otherwise used for the 2nd spare output and this is set up to handle a fair bit of current in a TO-220 transistor placed on the heat sink.

Output 5 is on the GPI2 circuit (Amp pin 6) and will require a number of mods (possibly on a proto board) to make a usable solenoid driver circuit. Note that this circuit is normally used with switchB for the manual lever, so you have to use a voltage based shifter to use this circuit as a solenoid driver.

Output 6 is on the EGT3 circuit (Amp pin 25), and will require a number of mods (possibly on a proto board) to make a usable solenoid driver circuit. Note that this circuit is normally used with switchC for the manual lever, so you have to use a voltage based shifter to use this circuit as a solenoid driver.

So you will have to see which of these work best for your transmission's electrical requirements. You can set the ON/OFF behavior of any of these in any gear ( http://www.msgpio.com/manuals/mshift/V2tune.html#h ), so the pattern you need won't depend on the shift logic (only Output 3 is different - it can have a third value that isn't OFF or ON while shifting, if you desire).

In most cases, the best bet is to use Outputs 1 to 4, and select the use of Output 3 if you need it's different shift state. If you have only one PWM solenoid, put this on Output 3 if you can - it has the most accurate and efficient PWM. If none of the solenoids are PWM'd, it won't matter which solenoids you select for which outputs.

Lance.
"Never wrestle with pigs. You both get dirty and the pig likes it." - George Bernard Shaw
Jim Blackwood
Posts: 222
Joined: Tue Dec 07, 2010 9:52 am

Re: AA80E 8-speed

Post by Jim Blackwood »

Thanks for the link Lance, I've got a better idea now of how this will work. We won't be able to enable some of the more advanced features but I think it'll be OK. Enough to start with anyway.

Solenoids SL1 through SL5 (Clutches 1 through 4 and Brake 1) are big, high flow PWM solenoids. They control shift firmness directly, as opposed to using line pressure to do it.

SLU (TCC/B2) and SLT (Line pressure reduction) are also PWM but are physically smaller. So we have 7 actual PWM solenoids to deal with, but we may find enough redundancy to run one or more as on/off solenoids. Probably not optimal but I'm guessing it could work.

SR (clutch sequence) and SL (TCC/Reverse) are on/off solenoids. For those we just have to find enough driver circuits.

I have pasted the drawing of the valve body and solenoids to the spreadsheet and will upload it once I have added enough to make it worthwhile. This drawing is in the largest of the AA80E files about 1/3 of the way down.

I have assigned PWM3 (pin 33) to solenoid SLT (line pressure reduction), although I suspect this solenoid may not play nearly as active a role as the line pressure control does in the GM tranny. However it might be a benefit to keep the settings for the shift solenoids as uniform as we can across at least SL1 through SL4 if we can. SL5 being a brake may behave a bit differently.

I'm still trying to get my head around the power flow through the transmission and the sequence of clutch/brake apply and release. I find the Lexus logic tables a bit confusing so I may work up something on my own as I figure it out. I think we are going to have to have that knowledge as there are either 50 or 100 possible apply/release combinations depending on whether the TCC/Reverse solenoid (SL) comes into play. That is on the agenda for today but it looks to be a fairly tough nut to crack. There may be scenarios where we can run one or more of the big PWM solenoids as on/off and get acceptable driveability.

JB
Bernard Fife
Posts: 1696
Joined: Fri Apr 04, 2008 1:28 pm

Re: AA80E 8-speed

Post by Bernard Fife »

Jim,

I forgot to mention that the bit banged outputs (1, 2, 4, 5, 6) in my post above currently all must have the same PWM frequency and duty cycle. This is usually the case for most transmissions, but perhaps not all. If necessary, I could change this if it is generally useful. Output3 has independent PWM on the timer channel.

The TCC and pressure control solenoids should not be a problem, these functions are already in the code, and have dedicated outputs. If your main controller has TCC control (either dedicated or through spare output settings), it isn't impossible that might be able to be used for the second TCC/Reverse SL solenoid).

SL1 to 5 can presumably be controlled by the Outputs 1 through 5 (Output5 will need some circuit modifications). However, Output5 is only available if using a voltage based shifter (a digital shifter using multiple inputs can often be converted to a voltage based shifter using a pull-up voltage a a number of resistors).

There are the spare outputs as well (both on the GPIO and any other controollers you have on the CAN network). There is also the possibility that some of the outputs could be run directly off the shift lever input (i.e. use one or more pins of the lever input to control a separate transistor for an output), if they are suitable arranged (I haven't looked at the logic to see if this is possible).

I need to understand what isn't in the controller in terms of I/O that you will need, and then if it is possible I can try to implement what you require.

Lance.
"Never wrestle with pigs. You both get dirty and the pig likes it." - George Bernard Shaw
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