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USB low-full-high speed peripherals Forum Discussions

JeBo_4132831
Level 4
Level 4
25 replies posted 25 sign-ins 10 replies posted

Hi,

I notived that the I2C speed of my I2C transactions are not 100KHZ but rather 85KHZ. 

When 400KHZ mode is selected,  speed is also lower than 400KHZ (less than 300 ...).

In my code, i set the CPU clock to 48MHZ.

// Configure CPU Clocks
// 48 MHZ // CLK_OUT ON (for Debug)
CPUCS = (bmCLKOE | bmCLKSPD1) & ~bmCLKSPD0;
SYNCDELAY;

Any idea why such low I2C frequency ? 

Do i need to configure something in the code ? I used the FX2LP template ECLIPSE project for my Firmware.

Thanks.

 

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1 Solution
PranavaYN
Moderator
Moderator
Moderator
500 replies posted 250 solutions authored 50 likes received

Hi, 

Do I need to configure something in the code ?

>> Configuration looks fine. No additional changes required.

It is expected that I2C of FX2LP18 runs at a lesser frequency than configured. 

Best regards,
Pranava

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3 Replies
PranavaYN
Moderator
Moderator
Moderator
500 replies posted 250 solutions authored 50 likes received

Hi, 

Do I need to configure something in the code ?

>> Configuration looks fine. No additional changes required.

It is expected that I2C of FX2LP18 runs at a lesser frequency than configured. 

Best regards,
Pranava
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JeBo_4132831
Level 4
Level 4
25 replies posted 25 sign-ins 10 replies posted

OK i saw the little one (1) on the datasheet ….

Why Do you say it is 100K and 400K in main characteristics ? It’s really non sense to add a small (1) to say that finally the speed is 15% less …. ☹

 

 

JeBo_4132831_0-1610955184397.png

 

 

  1. The actual I2C clock frequency will be different. The measured I2C clock frequency when set for 100 kHz and 400 kHz is around 85 kHz and 300 kHz respectively.

 

IS there any chance to obtain 100KHZ or definitively not ?

Regards

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PranavaYN
Moderator
Moderator
Moderator
500 replies posted 250 solutions authored 50 likes received

Hi,

We are extremely sorry that you were misled by the datasheet. 
There is no way obtain 100kHz or 400kHz I2C CLK frequency.

 

Best regards,
Pranava
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