Can I use the AN2295 bootloader running at 115200 with the internal RC oscillator?

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Can I use the AN2295 bootloader running at 115200 with the internal RC oscillator?

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Limestone
Contributor III

Hi!

 

In order to save the cost of a crystal, I would like to be able to run the AN2295 bootloader in with the interanal RC oscilator calibrated t0 36 khz and, if possible, communication at a bitrate of 115200.

 

My PCB features a QE128 and a 4Mhz crystal.

Currently, the internal RC oscillator is calibrated to 32.768 kHz and the bootloader runs at a fast enough 38400. However, the usercode needs 115200, and therefore, the user code use the 4Mhz crystal instead, since 32.768 can't be used to generate 115200.

 

However, If I calibrate the internal RC- oscillator to 36 kHz, I can set the usercode generate 115200 from it (done through PE). If I do that however, the bootloader will not  generate its 38400.

 

In essence, I have no need a bitrate of 115200 in the bootloader. I do however need it to operate correctly with a 36khz (or other frequency that can be used for 115200 in user code) internal oscillator speed.

 

Have I made myself clear enough?

Can this be done at all?

 

Best regards

Martin

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ok2ucx
Contributor IV

Sure you can. The absolute SCI speed is not important, no matter whether you communicate 1200Bd or 115200Bd, it is still roughly +/-3% tolerance into which you need to fit (assuming the physical interface works correctly).

 

Pavel

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