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5 years, 2 months ago.

about Mbed 1768

hello all

i want to know maximum frequency of Mbed 1768 by I2C.

thanks

2 Answers

Paul Staron
5 years, 2 months ago.

Specs are given in bits/sec.

check page 32 of the LPC1768 data sheet:

https://www.nxp.com/docs/en/data-sheet/LPC1769_68_67_66_65_64_63.pdf

400 kbit/s is the standard (fast) nowadays (check the device data sheet, old ones are 100kbit/s) and can run up to 1 Mbit/s. but that depends on the i2c device itself and device to MCU distance . I think I saw a 3.4Mbit/s (high speed mode) somewhere, but never used one.

Depending on the message length you are looking at around 50% - 90% data/frequency ratio to account for start/stop etc. overheads, the longer the message the less overheads.

Generally, set the i2c frequency to the same as the bit/s indicated on the device.

Wim Huiskamp
5 years, 2 months ago.

I think the highspeed I2C engine is not available on the LPC1768 mbed because the SDA/SCL pins are not accessible on the external header. Best you can get is probably 400kb