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73 lines
2.6 KiB
73 lines
2.6 KiB
7 years ago
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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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those are 6 central pins from on the top 10-pin row of
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ESP32 chip (only 2 pins on left side and 2 pins on right
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side shuould be connected). Either cut the traces or carefully
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solder without touching SD card pins.
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# What is fixed
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Shutdown:
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on assembled PCB v1.7, D11=1N4148 and R4=15k will
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keep waking the board up 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 wakeup 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 so alternative patch is
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to connect 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 won't tolerate that. Data traffic at i2c will be
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errorneously received by some monitors and some serious problem may arrise
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if monitor interprets some data garbage as random write command, overwriting
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its internal settings, then monitor will become useless.
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Correct pull up resistors are 4.7k and they work properly.
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WIFI:
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On PCB v1.7, SD card is connected to ESP32 pins that are widely advertised
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as SD card pins, but the problem is those pins are shared with internal flash
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chip and ESP32 won't boot from its SPI FLASH if anything is connected there.
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SD card should be connected on some other pins, probably HSPI. It has not
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yet been verified will that work.
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