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Question
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I am trying to connect New Haven Display NHD-5.0-800480Tf-ATXL#CTP touchscreen with i2c touchpanel to igepv2 using i2c3 on pins JA41 27, 28. I built a separate interface board using TXS0102DCUR translator with 4.7k pullup resistors and 100k OE resistor wired exactly as per IGEP Berlin and IGEPv2 EDID I2C interface on ISEE schematics. But I am getting very strange results
Using i2cdetect -r 3 I find
I2c3 on HDMI works fine when connected to a screen giving 37,3a and 70 addresses
I2c3 does not find touchscreen when HDMI detached and pins 27,28 attached to interface board as above.
I used an oscilloscope to test the i2c3 signals on pins 27,28 - no device attached but issuing i2cdetect -r 3 commands to send signals.
post-TXS0102 I get a SCL signal 3.3v but no SDA signal via i2cdetect -r 3 (SDA stays at 3.3v)
pre-TXS0102 I get SCL 1.8V signal and SDA=0V via i2cdetect -r 3
My connector board schematic is attached. Is there anything obviously wrong? Am I missing something? Does HDMI need to be shut down somehow in software?
< see attachment>
Using i2cdetect -r 3 I find
I2c3 on HDMI works fine when connected to a screen giving 37,3a and 70 addresses
I2c3 does not find touchscreen when HDMI detached and pins 27,28 attached to interface board as above.
I used an oscilloscope to test the i2c3 signals on pins 27,28 - no device attached but issuing i2cdetect -r 3 commands to send signals.
post-TXS0102 I get a SCL signal 3.3v but no SDA signal via i2cdetect -r 3 (SDA stays at 3.3v)
pre-TXS0102 I get SCL 1.8V signal and SDA=0V via i2cdetect -r 3
My connector board schematic is attached. Is there anything obviously wrong? Am I missing something? Does HDMI need to be shut down somehow in software?
< see attachment>
Accepted Answer
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Hi peter,
In idle state, I2C3_SDA must be pulled high (1V8). Do you have the same behaviour, I2C3_SDA pulled low, when your expansion board is plugged and unplugged from IGEPv2?
Cheers!
PD: In your hardware design, resistors R3 and R4 are not necessary, because IGEPv2 has pullup resistors into I2C3 1V8 bus
In idle state, I2C3_SDA must be pulled high (1V8). Do you have the same behaviour, I2C3_SDA pulled low, when your expansion board is plugged and unplugged from IGEPv2?
Cheers!
PD: In your hardware design, resistors R3 and R4 are not necessary, because IGEPv2 has pullup resistors into I2C3 1V8 bus
Responses (4)
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Accepted Answer
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Accepted Answer
0Thanks for the response. Yes, the I2C3_SDA is low when my expansion board is not connected. With your response, I can think of only 3 possible reasons.
1. The ribbon cable which I used to connect the JA41 header to the expansion board (and the oscilloscope) is faulty.
2. My soldering of the JA42 header to the IGEPv2 board is faulty.
3. I somehow fried something in the IGEPv2 board to cause this behaviour.
I will experiment and post my results. Thanks for the hint on my connector board design. I will fix that as well.
Peter -
Accepted Answer
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