Vida CEM swapping

[Sh4rp]

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[vtl]

My understanding is that in P1 one chip serves one CAN-bus. The question was: what bus is served by DT256B chip?

[loglofan]

Code: Select all

.data:0003fe38 34                               pshx
.data:0003fe39 35                               pshy
.data:0003fe3a b7 46                            tfr  D,Y

Hi vtl! Is it disassebled using IDA? I was using IDA for a while ago. It would be nice to install it again and try to analyze

[vtl]

Hi vtl! Is it disassebled using IDA? I was using IDA for a while ago. It would be nice to install it again and try to analyze

https://onlinedisassembler.com/odaweb/

[ZRimaZ]

My understanding is that in P1 one chip serves one CAN-bus. The question was: what bus is served by DT256B chip?

Once again - 256 chip on the bottom of the picture above is 8MHz chip and it serves HS CAN. The one on the top, in this case - 128, is for LS CAN. In some cases (depends on CEM HW PN) chip on the top is 256, as well as both chips could be 384kB chips (for example with HW PN 31268178)

[RickHaleParker]

Once again - 256 chip on the bottom of the picture above is 8MHz chip and it serves HS CAN.

8Mhz chip or the chip being clocked at 8Mhz?
In other words is the chip marked 8Mhz or do you look at the frequency on the oscillator.

[RickHaleParker]

This answers the question why is the CAN Bus 60ῼ when not loaded with a diagnostics interface.

The CEM is not a end node. There are two 120ῼ terminating resistors in whatever control modules are the end nodes.

For each CAN Bus HS and LS, the CEM has a Diagnostic CAN port to the J1962 ( OBDII ) connector. Then two others for the same CAN Bus that lead out to the other control modules on that CAN Bus. Three total for a CAN Bus, Six total for a CEM.

The two others is where you install 120ῼ resistors for Bench terminating. You need a total of four 120ῼ resistors for bench testing. Two for CAN HS and Two for CAN LS. Do not terminate the CAN diagnostics port to the J1962 connector.

No termination resistors on the PIN cracker because the CEM is not a end node. I'm taking the terminating resistors out of the ODIN CAN Shield design. Bench crackers you now know how to properly terminate the CEM for bench testing. Do it the proper way you should get better results. If you do split termination you can get even better results.

[RickHaleParker]

Took the Terminating resistors out and the switches. That really simplified things.
This one will drop into a ELM327 style case with a Folded J1962 connector.

Got one more mechanical dimension to verify then I should be ready to order the first board and test the performance. Anybody got PG7 cable glands laying around. I need the nut size dimension and I also need to know how far one will stick into the case.

Next I am going to do a Type B for 90° J1962 connectors. That should gain enough room to install and use Female headers so the end user can reuse the Tennsy 4.0 for other projects.

[ZRimaZ]

8Mhz chip or the chip being clocked at 8Mhz?
In other words is the chip marked 8Mhz or do you look at the frequency on the oscillator.

If you check the chips, no one has frequency mark on it. I meant the chip, clocked at 8MHz - this you can check on the quartz resonator - the metal barrel next to the chip.

[ZRimaZ]

2022-01-27 (1).png

Rick, I do not see 10k resistors on the board. I missed something or you missed it? Which transceivers are going to put in? Do they not need resistors?