Add test board documentation (#3359)
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Philip Gladstone
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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. The schematics
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are in [schematic](Test-harness-schematic-v1.pdf) and a rendering of the board is .
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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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There is an I2C bus hanging off DUT 0. Attached hardware is used both as
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tests of modules directly and also to facilitate testing other modules
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(e.g., gpio).
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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
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At address 0x20. An 16-bit tristate GPIO expander, this chip is used to
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test I2C, GPIO, and ADC functionality. This chip's interconnections are
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as follows:
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MPC23017 | Purpose
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---------|--------------------------------------------------------------
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/RESET |DUT0 reset. This resets the chip whenever the host computer resets DUT 0 over its serial link (using DTR/RTS).
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B 0 |4K7 resistor to DUT 0 ADC.
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B 1 |2K2 resistor to DUT 0 ADC.
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B 2 |Direct to DUT1 RST
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B 3 |Direct to DUT1 D3
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B 4 |When low, connects the alternate UART pins on DUT0 to RX,TX on DUT1
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B 5 |DUT1 GPIO16/WAKE via 4K7 resitor
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B 6 |DUT0 GPIO13 via 4K4 resistor and DUT1 GPIO15 via 4K7 resistor (also feeds in the primary TX from DUT1 when enabled by B4)
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B 7 |DUT0 GPIO15 via 4K7 resistor and DUT1 GPIO13 via 4K7 resistor (also feeds the primary RX on DUT1 when enabled by B4)
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Notes:
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- DUT 0's ADC pin is connected via a 2K2 reistor to this chip's port
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B, pin 1 and via a 4K7 resistor to port B, pin 0. This gives us the
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ability to produce approximately 0 (both pins low), 1.1 (pin 0 high,
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pin 1 low), 2.2 (pin 1 high, pin 0 low), and 3.3V (both pins high)
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on the ADC pin.
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- Port B pins 6 and 7 sit on the UART cross-wiring between DUT 0 and
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DUT 1. The 23017 will be tristated for inter-DUT UART tests, but
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these
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- All of port A, remain available for expansion and are routed to the breadboard area.
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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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#### 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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#### 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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#### 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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#### 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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ESP8266 Device 0 Connections
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----------------------------
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ESP | Usage
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----------|----------------------------------------------------------
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D3/GPIO 0 |Used to enter programming mode; otherwise unused in test environment.
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TX/GPIO 1 |Primary UART transmit; reserved for host communication
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D4/GPIO 2 |[reserved for 1-Wire] [+ reserved for 23017 INT[AB] connections]
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RX/GPIO 3 |Primary UART recieve; reserved for host communication
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D2/GPIO 4 |I2C SDA. Connected to MCP23017, Oled display and the TCS34725 if present.
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D1/GPIO 5 |I2C SCL
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GPIO 6 |[Reserved for on-chip flash]
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GPIO 7 |[Reserved for on-chip flash]
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GPIO 8 |[Reserved for on-chip flash]
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GPIO 9 |[Reserved for on-chip flash]
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GPIO 10 |[Reserved for on-chip flash]
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GPIO 11 |[Reserved for on-chip flash]
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D6/GPIO 12 |
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D7/GPIO 13 |Secondary UART RX; DUT 1 GPIO 15, I/O expander B 6
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D5/GPIO 14 |
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D8/GPIO 15 |Secondary UART TX; DUT 1 GPIO 13, I/O expander B 7
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D0/GPIO 16 |
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A0/ADC 0 |Resistor divider with I/O expander
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ESP8266 Device 1 Connections
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----------------------------
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ESP | Usage
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----------|----------------------------------------------------------
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D3/GPIO 0 |Used to enter programming mode; otherwise unused in test environment.
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TX/GPIO 1 |Primary UART transmit; reserved for host communication
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D4/GPIO 2 |Connected to chain of 3 WS2812s. Also connected to the servo position.
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RX/GPIO 3 |Primary UART recieve; reserved for host communication
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D2/GPIO 4 |I2C SDA. Connected to all the other I2C positions on the board
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D1/GPIO 5 |I2C SCL
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GPIO 6 |[Reserved for on-chip flash]
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GPIO 7 |[Reserved for on-chip flash]
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GPIO 8 |[Reserved for on-chip flash]
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GPIO 9 |[Reserved for on-chip flash]
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GPIO 10 |[Reserved for on-chip flash]
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GPIO 11 |[Reserved for on-chip flash]
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D6/GPIO 12 |Connected to data pin for DHTxx
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D7/GPIO 13 |Secondary UART RX; DUT 0 GPIO 15, I/O exp B 7 via 4K7 Also used as HSPI MOSI for SPI tests
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D5/GPIO 14 |Connected to data pin for DS18B20s.
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D8/GPIO 15 |Secondary UART TX; DUT 0 GPIO 13, I/O exp B 6 via 4K7 Also used as HSPI /CS for SPI tests
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D0/GPIO 16 |I/O expander B 5 via 4K7 resistor, for deep-sleep tests
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A0/ADC 0 |
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@ -124,6 +124,8 @@ 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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A particular implementation of this can be found at [Test Harness](HardwareTestHarness.html).
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## Peripherals
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### I2C Bus
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Binary file not shown.
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