I2C timing spec

RE: I2C timing spec

Håkon Alseth — Tue, 10 Mar 2020 08:29:16 GMT

[quote user="peanutbutter"]I understand it now. The spec on the datasheet meets the requirement by the I2C standard.[/quote]

Glad to hear! I had to read it a couple of times myself before it started to make sense.

Let us know if anything else pops up.

Cheers,

Håkon

RE: I2C timing spec

peanutbutter — Tue, 10 Mar 2020 03:55:00 GMT

I understand it now. The spec on the datasheet meets the requirement by the I2C standard.

RE: I2C timing spec

peanutbutter — Mon, 09 Mar 2020 15:37:03 GMT

I'm confused. The Tsu_dat is 300ns min so anything smaller 300ns is a failure. eg. That indicates that a Tsu_dat of 150ns will fail the NRF spec but 150ns is greater 100ns of NXP I2C spec.

RE: I2C timing spec

Håkon Alseth — Mon, 09 Mar 2020 14:49:49 GMT

Hello,

[quote user=""]Tsu_dat (300ns min) and Thd_dat(500ns min) are more stringent than NXP I2C spec.(Fast mode)[/quote]

Isn't this the other way around? We guarantee that the setup time is extended to allow slow I2C slaves to get "extra time" to prepare themselves for a command. If we had a minimum setup time (t_su;dat) that was lower than 100 ns, then we could have created a compatibility problem with slaves that require more than 100 ns to prepare its bus interface.

[quote user=""]Since most IC vendors design their I2C bus with NXP I2C spec, they are not meeting the nRF spec. Does nRF work reliably with NXP I2C spec Fast Mode spec?[/quote]

We have not gotten feedback, that I know of, that we do not work with certain devices.

We have a theoretical place where we can potentially break the I2C spec from NXP, where we can go under the minimum "tlow" defined parameter for fast mode:

https://infocenter.nordicsemi.com/topic/errata_nRF52840_Rev2/ERR/nRF52840/Rev2/latest/anomaly_840_219.html#anomaly_840_219

Kind regards,

Håkon