Toyota A750f Transmission control

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.
Paulwolf
Posts: 9
Joined: Thu Aug 12, 2010 1:07 am

Toyota A750f Transmission control

Post by Paulwolf »

hello, just wondering if anyone has used one of these GPIO (MegaShift) controllers on the 5 speed toyota A750f, (or any toyota transmission), it looks to have seven solenoids and several look to be PWM. I am yet to locate much info on this transmission, but I have come across this PDF http://www.ezdries.net/Vidpics/temp/A75 ... ission.pdf. It explains a little about how this thing works.

Thanks
Paul
Paulwolf
Posts: 9
Joined: Thu Aug 12, 2010 1:07 am

Re: Toyota A750f Transmission control

Post by Paulwolf »

Righto, I have delved a little deeper into the transmission side of things. Looks like it needs 3 general on/off outputs for first to third gears, 1 normal pwm for the torque convertor lockup, one inverse pwm for the line pressure control. 4th and 5th gear uses a variable solenoid (same construction as the tcc and line press) so could be pwm controlled too, however, I am pretty sure they are varied to provide silky gear changes. These could probably be fixed output with a resistor, if I knew how hard the had to switch on


Newby question, If I have a pwm output set to 100%, is it the same a general ouput set to 'on'?


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

Re: Toyota A750f Transmission control

Post by Bernard Fife »

Paul,

This looks similar to the 4L60E and could probably be mostly accommodated with the current code, except for the 4-5th solenoid. You *might* be able to use the Lock-Up Feel Parameters (http://www.msgpio.com/manuals/mshift/4L60E_MT.html#ll) to control this solenoid with some small code changes (changing the conditions from being dependent on the TCC state and load to being dependent on the shift table and load).

You would also need changes to accommodate 5th gear in the shift table, etc.

Since a number of people seem to want to control 5 speed (and higher) transmissions, I will put this in the code (it won't be released for a little while, though - until we have more feedback on the current code - hopefully weeks rather than months).

In the meantime, you can study the A750f transmission docs, and let us know in detail how they line up with the MShift inputs and outputs:
http://www.msgpio.com/manuals/mshift/hardware.html
http://www.msgpio.com/manuals/mshift/4L60E_MT.html
http://www.msgpio.com/manuals/mshift/wiring.html

Lance.
"Never wrestle with pigs. You both get dirty and the pig likes it." - George Bernard Shaw
Paulwolf
Posts: 9
Joined: Thu Aug 12, 2010 1:07 am

Re: Toyota A750f Transmission control

Post by Paulwolf »

Lance, The lock up feel parameters are very similar, I think that they function exactly the same as the variable shift solenoids for 4th and 5th in the a750. I also dont think its needed, i am more worried about burning the clutch or band, than undetectable shifts on the highway.

Although, because the tcc is locked in 4th and 5th, it might also provide a little 'give' for the change into 5th.
Probably could get the same result unlocking the convertor on the gear change

Factory ECU monitors the input and output speed and determines how hard to pressurise the clutch and band circuits in 4th and 5th. I think if the controller was dedicated to the a750 it could be done as per factory, but not sure if it is necessary, it is still adjustable maually via pwm control. Once it is set correctly for proper shift it shouldnt need altering again.

Paul
Paulwolf
Posts: 9
Joined: Thu Aug 12, 2010 1:07 am

Re: Toyota A750f Transmission control

Post by Paulwolf »

I have done up a table for the MegaShift hardware and how it will work in my application
MegaShift.xls
it all lines up fine, except the 4,3,2,1 inputs to show when manual selector is each low gear, need to find 2 more inputs or I need to find another way of inputting 7 signals on one channel.

I will post up the shift tables, when I have converted them

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

Re: Toyota A750f Transmission control

Post by Bernard Fife »

Paul,

I can't read that table, it's a bit too small. However, I think you are saying that the shift lever position input requires 4 digital inputs. The 4L60E has 3 of these. The fourth we can either use an existing, but unused, input (most likely the 2/4WDinut, or possibly the the non-CAN MAP input, or the line pressure sensor input).

When I do the code mods (soon), I will put the 4/5th solenoid on the LUF output (i.e. PT3/Amp32 for the 4/5 solenoid and SPR2/PA0/VB2 for TCC) and the additional digital input on PE1/Amp5 (currently the 2/4WD input).

I suppose you could put in resistors and make the shit lever positon a variable voltage function read on a single ADC input like the Ford shifters, but with a lot of gears the differences between gears gets smaller and harder to read correctly under all conditions, so I wouldnt recommend this.

Lance.
"Never wrestle with pigs. You both get dirty and the pig likes it." - George Bernard Shaw
Paulwolf
Posts: 9
Joined: Thu Aug 12, 2010 1:07 am

Re: Toyota A750f Transmission control

Post by Paulwolf »

Yeah sorry bout the table, tried to post it as a picture, but not successful. I have converted it to pdf, but cant find a way to host the file. * EDIT * - I have added it as an Excel file

As for the shifter inputs, I have P/N on one input, then R, then D. Need 4 more inputs, and only space for 2. So at this stage, in its current configuration, I can have the manual / auto and up down paddle shift OR the factory manual shifter inputs for low gear selection but not both.

I want the paddle switching feature, the reason I jumped on this controller, so I have to find a way of inputing the shifter selections.

I thought of analogue voltage inputs, but with 8 of them spread across 5 volts, not much separation. Perhaps I can use PN, R, and D as I have, then use an analogue input for 4321.

I will fix the table up, today

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

Re: Toyota A750f Transmission control

Post by Bernard Fife »

Paul,

You may not need 4 more inputs, it may be a pattern of inputs that defines the gears. With 3 inputs you can have up to 8 unique combinations (000, 001, 010, 011, 100, 101, 110, 111). This is what the 4L60E uses. 4 inputs gives up to 16 possible gear combinations.

It isn't immediately clear to me how your transmission shift lever inputs work, and I didn't find anything in a quick look through the PDF you posted (the outputs are shown, but I didn't see the inputs listed anywhere).

Lance.
"Never wrestle with pigs. You both get dirty and the pig likes it." - George Bernard Shaw
Paulwolf
Posts: 9
Joined: Thu Aug 12, 2010 1:07 am

Re: Toyota A750f Transmission control

Post by Paulwolf »

Lance, I have attatched a PDF (Finally worked out how) of the shifter inputs, PRN431 are direct inputs on their own, 5 and 2 require 2 inputs (4 and 5 for 5th gear, 2 and 1 for 2nd gear)
A750f- shifter inputs.pdf
(50.41 KiB) Downloaded 1473 times
Paul

PS I have added the table from last week as an Exel file
MegaShift.xls
(20 KiB) Downloaded 758 times
Bernard Fife
Posts: 1696
Joined: Fri Apr 04, 2008 1:28 pm

Re: Toyota A750f Transmission control

Post by Bernard Fife »

Paul,

It looks to me like there are 5 shifter position switches going to the ECM on pins 8, 11, 21, 19, and 10.

These appear to be laid out as follows:

pin 8 = Neutral
pin 11 = Reverse
pin 21 = Drive
pin 19 = 3rd
pin 10 = 2nd
(The stock shifter doesn't appear to have a 1st.)

How you read these depends on what you are going to do with the other electronics (engine, ABS,...). If you are going to do away with those, you could put voltage dividing resistors in the circuit and make the shift lever position voltage based (like the Ford shifters). You could even use a custom arrangement for this to get 1st - by modifying the stock shifter or using a ford shifter or something else.

If you want to piggy-back off the current config (and it's 12V pull-up), then 4 switches is enough. You would hook up pins 11, 21, 19, and 10 as the digital inputs. If these are all low, then you must be in P/N. If any one of them is pulled low, then that is the selected gear. If two or more are pulled low then there is an error in the shifter or the hardware.

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