Compatibility warning - High speed processor setting + CAN interface

[Crashmatt]

CANbus is not compatible with the new high speed processor setting.

CANbus needs to have a more accurate clock than UART.
The high speed processor setting is based on the free running clock
which does not have good enough accuracy.

The basic version of CAN interface + MatrixPilot will not be supported
and is of limited long term use.

The UDB-IMU + CAN Autopilot version might work.

The outstanding problems are:
Reliable setting of gps home location
Reliable startup sequence
Reliable transport of flags and events across CANbus
Reliable detection and action on disconnected IMU
Adjusting the high frequency operation to the CAN interface.

This is a much higher risk solution than previously expected.

I will not be able to work on anything until next year.

Regards Matt

[William Premerlani]

Hi Matt,

I assumed that the new high speed clock setting would not be compatible with CANBUS, that is why it is offered as an option.

The UDB4 will be crystal controlled with a crystal that will be compatible with the frequency multiplier, so it should be compatible with CANBUS as well as support all UART BAUD rates.

I have not been following your CANBUS work Matt, so forgive me for asking the following questions:

1. The new high speed processor setting does enable all standard UART baud rates, up to almost 1 megabaud. Would it be possible, and make any sense, for you to adapt your system to use the UART?

2. The fast RC oscillator that is used in the implementation of the new high speed setting has the option of "fine tuning", there are bits to adjust the frequency up or down a bit from nominal. I did not look in to it yet, but would it be possible to use the fine tuning to adjust the clock to get CANBUS working?

Best regards,

Bill

[Crashmatt]

Bill,
Again for the benefit of this thread (and not reply to you only)

1. UART would work. It is a good idea to adapt it to UART for users
who do not wish to use CAN
This would take a little work and interfere with the existing
telemetry code so I will not implement it.
It does not solve the real problem which is the content of messages
rather than physical communication layer.

2.The FRC 1.5% tuning is not good enough for CAN. There is also no
temperature or room temperature error specification for it.

To understand what functions are where on the UDB-IMU setup, look at
the third page of this document
https://docs.google.com/viewer?a=v&pid=explorer&chrome=true&srcid=0B5SF4VCMDng5MzAzNDRiMjItZmYwYy00NGU2LWFkZjAtNGE1ZGRjNzVlZWE3&hl=en

Regards
Matt

On Dec 21, 10:38 pm, William Premerlani <wpremerl...@gmail.com> wrote:
> Hi Matt,
>
> I assumed that the new high speed clock setting would not be compatible with
> CANBUS, that is why it is offered as an option.
>
> The UDB4 will be crystal controlled with a crystal that will be compatible
> with the frequency multiplier, so it should be compatible with CANBUS as
> well as support all UART BAUD rates.
>
> I have not been following your CANBUS work Matt, so forgive me for asking
> the following questions:
>
> 1. The new high speed processor setting does enable all standard UART baud
> rates, up to almost 1 megabaud. Would it be possible, and make any sense,
> for you to adapt your system to use the UART?
>
> 2. The fast RC oscillator that is used in the implementation of the new high
> speed setting has the option of "fine tuning", there are bits to adjust the
> frequency up or down a bit from nominal. I did not look in to it yet, but
> would it be possible to use the fine tuning to adjust the clock to get
> CANBUS working?
>
> Best regards,
> Bill
>