112 lines
4.6 KiB
Markdown
112 lines
4.6 KiB
Markdown
Hardware Test Harness
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=====================
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There is an implementation of the hardware testing design which is a small 4in x 4in board with positions for
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two Wemos D! Mini ESP8266 boards, a breadboard area and a number of positions for peripherals. A rendering of the board is below and the [schematics](Test-harness-schematic-v1.pdf)
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are available as well: .
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The test harness runs from a dedicated host computer, which is expected
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to have reset- and programming-capable UART links to both ESP8266
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devices, as found on almost all ESP8266 boards with USB to UART
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adapters, but the host does not necessarily need to use USB to connect,
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so long as TXD, RXD, DTR, and RTS are wired across.
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The alternate pins on the primary D1 Mini (DUT0) are cross wired to the
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RX and TX pins on the secondary D1 Mini (DUT1) and these are enabled by
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a pin on the MCP23017.
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Build Notes
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-----------
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The only thing that needs to be done is to solder on 0.1" headers at the required
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positions. Typically D1 Minis come with 2 sets of 8 pin headers, both male and female.
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I solder the female headers to the board, and the maie headers to the D1 minis. Other,
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mostly 4 pin, headers can be soldered at the other positions. The 7 pin header for
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the color sensor (TCS34725) requires some care as the board needs to be mounted
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upside down so that the sensor is directly above the WS2812.
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The screw holes at the corners are for M3 screws. A standard adhesive rubber foot can
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also be used. There are no components on the underside of the test board, so not much clearance
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is required (only the length of the various headers soldered on the board).
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Power
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-----
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The board is powered by either (or both) D1 Mini USB connection. Given the cross connects
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between the two D1 Minis, I think that all the tests can be conducted from DUT0, but
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it is probably easier to connected both of the D1 Minis via USB to the test runner.
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There is a small resistor between the two 5 volt rails to prevent large currents
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if the two USB feeds are at slughtly different voltages. The 3.3 volt rails are
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directly connected together. If the regulators produce slightly different voltages,
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then the one producing the higher voltage will end up providing all the power for the
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3.3 volt devices.
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Peripherals
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-----------
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### I2C Bus
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Most of the positions on the board are connected to the DUT1 I2C bus.
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#### MCP23017: I/O Expander (DUT 0, 0x20)
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As per the [Generic Framework](README.md).
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### WS2812s
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There are three WS2812s connected on DUT1/D4. The last Ws2812 is positioned so that a TCS34725 module
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can be mounted upside down over it to read out the color of the WS2812. That device is connected to
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the I2C port on DUT0. A suitable board is [CJMCU-34725 TCS34725 Color Sensor RGB color sensor development board module](https://www.aliexpress.com/item/32412698433.html). The illuminating
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LED is connected to the INT pin and so you can disable the LED under software control.
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#### Oled Displays
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Each of the D1 Minis is connected to a position for a 128x64 OLED display, again on the primary I2C bus.
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Note: Not yet used in the test harness.
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#### Servo
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On DUT1 pin D4/GPIO 2 there is a connection to a position for a small servo. The servo is powered by the
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5V voltage rail.
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Note: Not yet used in the test harness.
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#### DHTxx
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On DUT1 pin D6/GPIO 12 there is a connection to a position for a DHTxx device. The silk screen indicates the
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orientation of the device.
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Note: Not yet used in the test harness.
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#### DS18B20
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There are two positions for DS18B20s -- one with the VCC pin connected and one without. The data pin is
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connected to DUT1 pin D5/GPIO 14.
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Note: Not yet used in the test harness.
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Note: It would make sense to augment the 1-Wire testing facility to
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include bus-drive power, perhaps via the MCP23017, especially if we ever
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augment the driver as per
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https://github.com/nodemcu/nodemcu-firmware/issues/1995
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#### I2C devices with VCC/GND/SCL/SDA pin order
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There are three positions for I2C devices which have the pins in the VCC/GND/SCL/SDA order. These
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are on the DUT1 I2 bus.
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#### I2C devices with other pin orders
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There are three positions for I2C devices with other pin orders. Each of these positions is next
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to a crossbar switch and so four blobs of solder can configure each of these headers into any
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desired pin order. As far as I can tell, most of the cheap modules use the VCC/GND/SCL/SDA order.
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Breadboard Area
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===============
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All the pins on each D1 Mini and the A port of the MCP23017 are brought out to a breadboard
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area. This can be used to solder components and/or wires, or even a header could be soldered
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on to transfer all the signals to a conventional breadboard.
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