AWR2944: MCAN bit rate calculation

Wesley He

Part Number: AWR2944

Hi team,

Can you please help to check, is my baud rate calculation for MCAN is correct? Thanks.

Configuration is from C:\ti\mmwave_mcuplus_sdk_04_02_00_02\mcu_plus_sdk_awr294x_08_01_01_06\source\drivers\mcan\v0\mcan.c

Formula is copy from TDA processor code.

/* Configuring default 1Mbps and 5Mbps as nominal and data bit-rate respectively */

if (bitTimes != NULL)
{
/* Initialize bit timings */
bitTimes->nomRatePrescalar = 0x7U;
bitTimes->nomTimeSeg1 = 0x5U;
bitTimes->nomTimeSeg2 = 0x2U;
bitTimes->nomSynchJumpWidth = 0x0U;
bitTimes->dataRatePrescalar = 0x1U;
bitTimes->dataTimeSeg1 = 0x3U;
bitTimes->dataTimeSeg2 = 0x2U;
bitTimes->dataSynchJumpWidth = 0x0U;
}

Bit rate calculation:
bit rate = ((mcan_clk / prescalar) / (Sum of timing parameters))
nomRate, mcan_clk = 80 MHz, prescalar = = (nomRatePrescalar + 1) = 8, Sum of timing parameters = (nomTimeSeg1 + nomTimeSeg2 + 3) = 10
bit rate = (80MHz / 8) / 10 = 1000 kbps

dataRate, mcan_clk = 80 MHz, prescalar = = (nomRatePrescalar + 1) = 2, Sum of timing parameters = (nomTimeSeg1 + nomTimeSeg2 + 3) = 8
bit rate = (80MHz / 2) / 8 = 5000 kbps

Thanks

Wesley

over 3 years ago

0 Akshay Kumar Chandrasekaran over 3 years ago

TI__Expert 8275 points

Hi Weasely,

Give me a day. I can check and get back if your calculations are correct.

Thanks and Regards,

Akshay.

0 Akshay Kumar Chandrasekaran over 3 years ago in reply to Akshay Kumar Chandrasekaran

TI__Expert 8275 points

Hi Weasely,

The MCAN bit rate calculation can be found in automotive toolbox from TIREX (you would need to download the entire toolbox for this). Go to the file: C:\ti\mmwave_automotive_toolbox_3_6_0__all\mmwave_automotive_toolbox_3_6_0\labs\lab0005_object_data_over_can\odoc-target\mss\mss_main.c (line no: 2345-2361). I have copy pasted the lines from code:

Request you to please go through the above code/suggestion and let me know if you have any question.

Thanks and Regards,

Akshay.

0 Wesley He over 3 years ago in reply to Akshay Kumar Chandrasekaran

TI__Expert 6205 points

Hi Akshay,

What i'm asking is the AWR2944. Not the AWR1x.

Please confirm that your reply can match the AWR2944 platform.

Thanks.

Wesley

0 Akshay Kumar Chandrasekaran over 3 years ago in reply to Wesley He

TI__Expert 8275 points

Hi Weasely,

The IP of MCAN used in 1st-gen is same as the one used for AWR2944. So this calculation should match the AWR2944 platform but give me sometime to double check with team internally and get back.

Thanks and Regards,

Akshay.

0 Akshay Kumar Chandrasekaran over 3 years ago in reply to Akshay Kumar Chandrasekaran

TI__Expert 8275 points

Hi Weasely,

Apologies for the delay. The snip attached in the above shows the data and nominal bit-rate calculation for AWR2944. The internal team confirmed it today.

Let me know if you have any questions.

Thanks and Regards,

Akshay.

0 Wesley He over 3 years ago in reply to Akshay Kumar Chandrasekaran

TI__Expert 6205 points

Hi Akshay,

Can you please let me know which one will be the correct one?

The one i posted? Or your post?

Thanks.

Wesley

0 Akshay Kumar Chandrasekaran over 3 years ago in reply to Wesley He

TI__Expert 8275 points

Hi Weasely,

The one I have posted as the snip (from TIREX) is the correct one.

Thanks and Regards,

Akshay.

0 Wesley He over 3 years ago in reply to Akshay Kumar Chandrasekaran

TI__Expert 6205 points

Hi Akshay,

OK. So, can you please let me know how the AWR2944 sdk code shown below can calculate the 1Mbps and 5Mbps? Thanks.

Configuration is from C:\ti\mmwave_mcuplus_sdk_04_02_00_02\mcu_plus_sdk_awr294x_08_01_01_06\source\drivers\mcan\v0\mcan.c

Line 2293-2312.

/* Configuring default 1Mbps and 5Mbps as nominal and data bit-rate respectively */

I cannot do it with your snip formula.

Thanks,

Wesley

+1 Akshay Kumar Chandrasekaran over 3 years ago in reply to Wesley He

TI__Expert 8275 points

Hi Weasely,

You are right. There are two ways CAN driver bit-rate(both nominal and data) are calculated it seems for MCAL CAN and non-MCAL MCAN (normal MCAN). I would request you to please look into this thread (Karan's answer): https://e2e.ti.com/support/processors-group/processors/f/processors-forum/920090/faq-tda4vm-can-how-is-bit-rate-calculated-for-can to get a detailed understanding (as implementation is slightly different in both cases). So from this thread it is clear that the snip I had posted from TIREX is for MCAL MCAN version while the one you have copy-pasted is for normal MCAN (the one present in C:\ti\mmwave_mcuplus_sdk_04_02_00_02\mcu_plus_sdk_awr294x_08_01_01_06\source\drivers\mcan\v0\mcan.c calculation is based on normal MCAN).

Let me know if you have further questions.

Thanks and Regards,

Akshay.

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AWR2944: MCAN bit rate calculation