Quote:
Originally Posted by DomesticExtremis
Well I stumbled across some info during my investigation of the TPS65185 chip. In the datasheet, section 8.37.
It seems that the PMIC can measure and save the adjustment value but how uboot or the kernel can be persuaded to make that happen I don't know. I have a suspicion that the second serial header on my Aura H2O is there for the purpose of doing that at the factory, so maybe that is the only possibility, no doubt you would need some special programmer to interface with it.
If some of you smart hackers can figure out how to do it, I'd be interested to sse the result.
ETA: here, maybe? |
Relevant section of the datasheet:
Quote:
8.3.7 VCOM Adjustment
VCOM is the output of a power-amplifier with an output voltage range of 0 V to –5.11 V, adjustable in 10-mV steps. In a typical application VCOM is connected to the VCOM terminal of the EPD panel and the amplifier is controlled through the VCOM_CTRL pin. With VCOM_CTRL high, the amplifier drives the VCOM pin to the voltage specified by the VCOM1 and VCOM2 register. When pulled low, the amplifier turns off and VCOM is
actively discharged to ground through VCOM_DIS pin. If active discharge is not desired, simply leave the VCOM_DIS pin open.
For ease of design, the VCOM_CTRL pin may also be tied to the battery or IO supply. In this case, VCOM is enabled with STROBE4 during the power-up sequence and disabled on STROBE1 of the power-down sequence.
Therefore VCOM is the last rail to be enabled and the first to be disabled.
8.3.7.1 Kick-Back Voltage Measurement
TPS65185x can perform a voltage measurement on the VCOM pin to determine the kick-back voltage of the panel. This allows in-system calibration of VCOM. To perform a kick-back voltage measurement, follow these
steps:
• Pull the WAKEUP pin and the PWRUP pin high to enable all output rails.
• Set the HiZ bit in the VCOM2 register. This puts the VCOM pin in a high-impedance state.
• Drive the panel with the Null waveform. Refer to E-Ink specification for detail.
• Set the ACQ bit in the VCOM2 register to 1. This starts the measurement routine.
• When the measurement is complete, the ACQC (Acquisition Complete) bit in the INT1 register is set and the nINT pin is pulled low.
• The measurement result is stored in the VCOM[8:0] bits of the VCOM1 and VCOM2 register.
The measurement result is not automatically programmed into nonvolatile memory. Changing the power-up default is described in the following paragraph.
8.3.7.2 Storing the VCOM Power-Up Default Value in Memory
The power-up default value of VCOM can be user-set and programmed into nonvolatile memory. To do so, write the default value to the VCOM[8:0] bits of the VCOM1 and VCOM2 register, then set the PROG bit in VCOM2 register to 1. First, all power rails are shut down, then the VCOM[8:0] value is committed to nonvolatile memory such that it becomes the new power-up default. Once programming is complete, the PRGC bit in the INT1 register is set and the nINT pin is pulled low. To verify that the new value has been saved properly, first write the VCOM[8:0] bits to 0x000h, then pull the WAKEUP pin low. After the WAKEUP pin is pulled back high, read the VCOM[8:0] bits to verify that the new default value is correct.
(plus a block diagram and flowchart)
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Simples
