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# PCB v1.7 upgrade
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This is the first board produced, most important
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parts work which is mirracle in itself, and there
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are some mistakes, luckily most of them can be fixed.
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FIX: Replace this parts:
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D11=LED (High efficiency RED recommended)
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R4,R25,R26=4.7k
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D11 and R4 are are on the back side on the left,
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under the edge of SDRAM chip.
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R25 and R26 are on the back side top,
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under the GPDI connector.
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Optionally, as alternative software shutdown,
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connected J2 "25-" pin to R13-D15 junction.
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Mount:
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SDCARD: SCHD3A0100
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U11 I2C: PCA9306D SOIC-8 150-mil
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U10 FLASH: IS25LP032D-JNLE-TR SOIC-8 150mil
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U9 WIFI: ESP32, but not all pins! read below:
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Don't connect ESP32 pins leading to SD card,
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in the top 10-pin row, connect only 2 pins on left side and 2 pins on right
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and leave 6 central pins unconnected. GND and VCC
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can be connected, but no other SD signal pins.
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Either cut the traces or carefully solder without
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touching those pads.
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# What is fixed
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Shutdown:
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PCB v1.7 assembled comes with D11=1N4148 and R4=15k, those will
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keep waking up the board after shutdown signal because FT231x internal
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regulator will provide enough voltage (cca 2.5V will appear at 3.3V line)
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and that is enough to wake up the board because voltage
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on ENABLE pin at switching regulators will be above its turn on
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threshold of 1.5V.
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Using higher voltage drop diode (RED, YELLOW or GREEN LED cca 1.7-2V, not
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BLUE or WHITE) and adequate resistor, the voltage at ENABLE pin is now about
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1.3V, inside of the switching regulator's hysteresis range. ENABLE is
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not above turn-on threshold neither below turn-off threshold so it will
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self-hold switching regulator during normal operation and at controlled
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shutdown signal, it will drop below turn-off threshold, allowing reliable
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shutdown.
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Software shutdown is not routed to BGA pads. It is possible to connect
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any GPIO (we recommend "25-") to SHUTDOWN.
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I2C:
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Too low pull up resistors (470 ohm) are at 5V side of the level converter PCA9306
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and some monitors will receive niose with that. If data traffic at i2c is
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not received 100% error-free, some monitors will get into serious problems.
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When monitor interprets some data garbage as random write command and
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overwrites its internal settings, such monitor might become premanently
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useless. Correct pull up resistors are 4.7k and they should work properly.
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WIFI:
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On PCB v1.7 SD card is connected to those ESP32 pins which are widely advertised
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as SD card pins, but those pins are shared with internal SPI FLASH.
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So ESP32 won't boot if anything is connected there.
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SD card could be connected on other pins, probably shared with OLED.
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It has not yet been tested, so no patch recommendation yet.
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