We are experiencing intermittant power up - initialization issues with the TSC2006 Touchscreen controller. (with AM1808 Micro)
In reviewing App report SBAA193 it appears that under certain power on/off conditions this device can enter a "specific test mode" for TI internal testing. A hardware reset alone cannot clear this mode per the App note.
In our case we see that the SDO line is always being driven low by the TSC2006, even when the CS line is high when this failure occurs (should be tri-state). The TSC2006 does not respond to touches or commands.
Does anyone have any details on the "TI Internal test mode" and how it influences the I/O pins if it's active. (we will try the suggested sequence for clearing the test mode)
There are about 16 internal test modes in TSC2006 that were design to test various internal state machines/functions/signals, where some TSC2006 pins may be used as status outputs or control inputs, depending on the internal test mode and being totally not related to the pins' external functions.
The internal test mode should never be entered under normal user's modes. Without proper POR, however, TSC2006 could randomly land on any status/mode. All random status/modes can be clear-up by hardware reset, except for one of these 16 internal test modes, which can be clear-up only by the sequence provided in sbaa193.
Note that, if the problem is related to the POR, it must be: (1) occurring only after a power-up or re-power-up (not in middle of operation with stable powering); (2) occurring randomly after a power-up or re-power-up (not at every power up re power up); and (3) the only way (without using the sequence provided in sbaa193) to get off from the problem is to recycle the power. If your problem meets the above three condition, it can be sure the POR problem described in sbaa193 and the suggested sequence should be implemented.
Thank you very much for the very informative answer, our conditions are exactly as you describe in 1, 2 ,and 3. I was fairly sure this was what we were seeing and your answer confirms it.
I have found that placing a load resistor on the power supply to improve the supply rise and fall times resolves the issue. We will also implement the reset sequence today, I am sure that will take care of the issue.
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