[Ovmsdev] OVMS Poller module/singleton

[Michael Balzer]

Simon,

you need to connect via USB to set the boot partition if you cannot 
access the module.

But… there is no way a wrong MCP2515 timing could cause this. I'd look 
for other potential causes.

Regards,
Michael


Am 26.01.25 um 13:58 schrieb Simon Ehlen via OvmsDev:
> Hi Michael,
>
> I tried your first suggestion, but after this change the OVMS no 
> longer boots at all.
>
> cnf1=0xc3; cnf2=0xaa; cnf3=0x85;
>
> What is the easiest way to select the firmware on the second 
> partition? Is there a way via the SD card or do I have to connect the 
> OVMS with USB?
>
> Cheers,
> Simon
>
> Am 26.01.2025 um 12:51 schrieb Michael Balzer via OvmsDev:
>> Simon,
>>
>> Am 25.01.25 um 21:00 schrieb Simon Ehlen via OvmsDev:
>>> Are adjustments/improvements also necessary at 125KBPS for CAN2/3?
>>
>> I've had a look at SAE J2284-1 for the 125 kbit timing, and it seems 
>> for this speed, the esp-idf, the mcp_can lib and our current driver 
>> are outside the spec.
>>
>> SAE recommends a sync jump width of 3 for low (nq=8) and 4 for higher 
>> resolutions, and single sampling at 62.5% (range 58.3…69.2%).
>>
>> The esp-idf driver would use a SJW of 3 (would better be 4 as nq=20) 
>> and single sampling at 80% (very late). The Arduino lib uses SJW=2 
>> (too low) and triple sampling at 75% (late).
>>
>> Our current driver uses a SJW of 1 (much too low) and triple sampling 
>> at 56.25% (too early):
>>     case CAN_SPEED_125KBPS:
>>       cnf1=0x03; cnf2=0xf0; cnf3=0x86;
>>       // BRP=3, PRSEG=1, PS1=7, PS2=7, SJW=1, BTLMODE=1, SAM=1, 
>> SOF=1, WAKFIL=0 → Sample 3x at 9/16 = 56,25%
>>
>> (Note: the current comment in the source is incorrect, the tq values 
>> need each to be read as +1)
>>
>> Possible SAE solutions for the MCP2515:
>>
>> a)
>>     case CAN_SPEED_125KBPS:
>>       // SAE J2284-1:
>>       // BRP=3, PRSEG=3, PS1=6, PS2=6, SJW=4, BTLMODE=1, SAM=0, 
>> SOF=1, WAKFIL=0 → Sample point at 10/16 = 62.5%
>>       cnf1=0xc3; cnf2=0xaa; cnf3=0x85;
>> b)
>>     case CAN_SPEED_125KBPS:
>>       // SAE J2284-1:
>>       // BRP=3, PRSEG=3, PS1=7, PS2=5, SJW=4, BTLMODE=1, SAM=0, 
>> SOF=1, WAKFIL=0 → Sample point at 11/16 = 68.8%
>>       cnf1=0xc3; cnf2=0xb2; cnf3=0x84;
>>
>> Please try.
>>
>> Btw, if anyone would like to experiment: the Microchip timing 
>> calculator needs to be set to 16 MHz (that's our MCP2515 clock), and 
>> you need to add 0x80 to the cnf3 byte generated (that's the SOF flag, 
>> cannot be set in the UI).
>>
>> Regards,
>> Michael
>>
>>
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>
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-- 
Michael Balzer * Am Rahmen 5 * D-58313 Herdecke
Fon 02330 9104094 * Handy 0176 20698926

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