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JeremyH
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Joined: 2014-07-17 08:33
I2C pullup resistors

Hello Dialog,

The DA14580 datasheet mentions that the i2c works in open drain mode.
However, I see a (valid) i2c signal without anything connected to the SDA / SCL pins, and no external pull up. The pins are configured as input without pull-up:
GPIO_ConfigurePin( I2C_SDA_PORT, I2C_SDA_PIN, INPUT, PID_I2C_SDA, false );
GPIO_ConfigurePin( I2C_SCD_PORT, I2C_SCD_PIN, INPUT, PID_I2C_SCL, false );

Can you please confirm whether there are internal pull up on the i2c pins?
If yes, what is their resistance? Can they be disabled?

Best,
Jeremy

Device: 
igotit
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Last seen: 4 years 4 weeks ago
Joined: 2015-03-16 03:52
Hi Jeremy,

Hi Jeremy,
1. The resistance is 25k for pull-up or pull-down.

2. if you access the register directly, the register Pxx_MODE_REG can be setted you want.
for example, page 121 from datasheet http://support.dialog-semiconductor.com/downloads/DA14580_DS_v3.1.pdf
P00_MODE_REG (address : 0x50003006 ) the bit9,8 pull-up, pull-down, no registor selectable.

Dialog's SDK function for these purpose,.. Please Dialog team ...

MT_dialog
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Joined: 2015-06-08 11:34
Hi igotit,

Hi igotit,

Thanks for indicating,

MT_dialog

JeremyH
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Last seen: 4 years 10 months ago
Joined: 2014-07-17 08:33
Hi Igotit, MT_Dialog,

Hi Igotit, MT_Dialog,

Thank you for your replies.
I've tried changing the P0x_MODE_REG, but it does not seem to have any effect on the I2C pins, the pull-up is always engaged.

Is there an additional step to disable the pull-up when in I2C mode, or another way to do it?

Thanks in advance,
Jeremy

MT_dialog
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Hi Jeremy,

Hi Jeremy,

You are right about that, we will have an answer for this as soon as we 've got some info from the hardware team. In the meantime can you please let us know why do you want to disable the pull-up ?

Thanks MT_dialog

JeremyH
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Last seen: 4 years 10 months ago
Joined: 2014-07-17 08:33
Hi MT_Dialog,

Hi MT_Dialog,

Thanks.
I need the I2C to work in an intermediate voltage domain (~2V), and I only have VBAT (~1.3V) and VBAT_3V pull up options.

Jeremy

MT_dialog
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Hi JeremyH,

Hi JeremyH,

As i was informed by the hardware team when you configure your pins in I2C functionallity there's no way to disable pull-up.

Thanks MT_dialog

JeremyH
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Last seen: 4 years 10 months ago
Joined: 2014-07-17 08:33
Hi MT_Dialog,

Hi MT_Dialog,

Ok, I'll find another way.
Thank you for letting me know.

Best,
Jeremy