fw: add libopencm3 submodule

.gitmodules

@@ -1,3 +1,6 @@
 [submodule "library"]
 	path = library
 	url = https://git.cuvoodoo.info/kingkevin/qeda_library
+[submodule "firmware/libopencm3"]
+	path = firmware/libopencm3
+	url = https://github.com/libopencm3/libopencm3

.qeda.yaml

@@ -1,8 +1,6 @@
 config:
   nodate: true
   output: kicad7
-  symbol:
-    pinIcon: false
   pattern:
     densityLevel: 'N'
     lineWidth:
@@ -10,7 +8,22 @@ config:
     polarityMark: none
     preferManufacturer: false
     smoothPadCorners: false
+  symbol:
+    pinIcon: false
 library:
   - resistor/r0603
   - capacitor/c0603
   - diode/led0805
+  - connector/usb-c_xkb_u262-24xn-4bv60
+  - connector/usb-micro-b-2.0_xkb_u254-051n
+  - connector/usb-a-3.0_xkb_u231-09xn-4blra00
+  - diode/led0603
+  - connector/usb-c_hro_type-c-31-m-17
+  - connector/battery_my-2032-12
+  - transistor/pmos_bss84
+  - transistor/nmos_bss138
+  - vreg/fuse_1206sfh
+  - vreg/ldo_torex_xc6206@mr
+  - diode/schottky@sod323
+  - mcu/st_stm32f030@lqfp48
+  - mechanical/smd-button_tx-1187a

CHANGELOG.md

@@ -0,0 +1,37 @@
+TODO:
+
+- make current draw zero when no cable is connected
+
+v1
+==
+
+changes:
+
+- make capabilities more compact
+- add interpretation purpose part
+- add button for battery usage
+- add connector presence test
+
+fixes:
+
+- BC test. I'm not sure what I had in mind but there were too errors: micro-B D- and D+ are shorted on the board (thus no way to detect the short in the plug), D-/D+ on the test would be left floating on plug with BC (thus would not turn the LED on)
+- VBUS test. On cables with ground wire, but no VBUS wire (such as A-C cable with not all GND or VBUS pin in C plug), the power ground would pull down VBUS through LED D1A for host A just enough to switch on Q1, lighting up LED D1C LED for host C
+- CC test: only for *-C cable. C to micro-B would also trigger it
+- and improve a lot of other tests
+
+issues:
+
+
+v0
+==
+
+first prototype containing testers for USB A, micro-B, and C.
+not tested yet.
+only shows the features, and does not interpret them.
+
+issues:
+
+- BC test is wrong
+- shield is detected although there is none (not sure why)
+- Rp is detected although there is none (not sure why)
+- red LEDs is too bright (1 kOhm current limiting resistor is too weak, 5.1k is better)

DEVELOPMENT.md

@@ -6,7 +6,7 @@ requirements
 to be able to generate the outputs, you need following software:
 
 - [QEDA](http://qeda.org/): to generate footprints for the parts
-- [KiCad v8](https://www.kicad.org/): EDA software used for schematic capture and board layout
+- [KiCad v7](https://www.kicad.org/): EDA software used for schematic capture and board layout
 - [PcbDraw](https://github.com/yaqwsx/PcbDraw): to generate board layout rendering
 - [KiKit](https://github.com/yaqwsx/KiKit): to generate fabrications files (Gerber, Excellon)
 - [KiBoM](https://github.com/SchrodingersGat/KiBoM): to generate Bill of Material (CSV)

Makefile

@@ -1,6 +1,6 @@
 # project file name (use for schematic and board layout)
-NAME ?= template
-SUBSHEET ?= 
+NAME ?= usb-microbc_cable_tester
+SUBSHEET ?= usb-microbc_cable_tester-mcu 
 # path to KiCad CLI
 KICAD = kicad-cli
 # path to qeda
@@ -33,12 +33,10 @@ VERSIONED_SHEET = $(foreach SHEET,$(NAME) $(SUBSHEET),$(SHEET).versioned.kicad_s
 FABRICATION_DIR := fabrication
 IBOM := ${FABRICATION_DIR}/ibom.html
 
-all: $(VERSIONED_SHEET) ${NAME}.sch.pdf ${NAME}.bom.csv render fab
+all: $(VERSIONED_SHEET) ${NAME}.sch.pdf ${NAME}.brd-top.png ${NAME}.brd-bot.png ${NAME}.bom.csv ${NAME}.3d.step fab
 
 fab: ${FABRICATION_DIR} ${IBOM}
 
-render: ${NAME}.brd-top.png ${NAME}.brd-bot.png ${NAME}.brd-top.svg ${NAME}.brd-bot.svg ${NAME}.3d.step
-
 # generate fabrication files (gerbers/drill/BoM/PnP)
 ${FABRICATION_DIR}: ${NAME}.versioned.kicad_sch ${NAME}.versioned.kicad_pcb
 	kikit fab jlcpcb --no-drc --assembly --field JLCPCB,LCSC --schematic $^ $@
@@ -70,14 +68,6 @@ lib:
 %.brd-bot.png: %.versioned.kicad_pcb
 	pcbdraw plot --silent --no-components --dpi 600 --side back $< $@
 
-# generate render from layout (top side)
-%.brd-top.svg: %.versioned.kicad_pcb
-	$(KICAD) pcb export svg --layers F.Cu,F.Paste,F.Silkscreen,Edge.Cuts --page-size-mode 2 --exclude-drawing-sheet --output $@ $<
-
-# generate render from layout (bottom side)
-%.brd-bot.svg: %.versioned.kicad_pcb
-	$(KICAD) pcb export svg --layers B.Cu,B.Paste,B.Silkscreen,Edge.Cuts --mirror --page-size-mode 2 --exclude-drawing-sheet --output $@ $<
-
 # export Bill of Material (as CSV)
 %.bom.xml: %.versioned.kicad_sch %.versioned.kicad_pro
 	$(KICAD) sch export python-bom --output $@ $<
@@ -91,22 +81,20 @@ lib:
 	$(KIBOM) $< $@
 
 # generate panel
-PANEL_DIR := panel_fab
-
-panel: panel.kicad_pcb panel.brd-top.svg panel.brd-bot.svg panel.brd-top.png panel.brd-bot.png ${PANEL_DIR}
-
-panel.kicad_pcb: ${NAME}.versioned.kicad_pcb ${NAME}.versioned.kicad_pro ${NAME}.versioned.kicad_sch panel.versioned.json
-	kikit panelize -p panel.versioned.json ${NAME}.versioned.kicad_pcb $@
+PANEL_DIR := panel
+panel: panel.kicad_pcb
+panel.kicad_pcb: ${NAME}.versioned.kicad_pcb ${NAME}.versioned.kicad_pro ${NAME}.versioned.kicad_sch ${NAME}.versioned.json
+	kikit panelize -p ${NAME}.versioned.json ${NAME}.versioned.kicad_pcb $@
 	sed --in-place 's/\"missing_courtyard\": \"warning\"/\"missing_courtyard\": \"ignore\"/g' $(patsubst %.kicad_pcb,%.kicad_pro,$@) # the mouse bites don't have a courtyard
-
-${PANEL_DIR}: ${NAME}.versioned.kicad_sch panel.kicad_pcb
-	kikit fab jlcpcb --assembly --missingError --field JLCPCB,LCSC --schematic $^ $@
+	kikit fab jlcpcb --assembly --missingError --field JLCPCB,LCSC --schematic ${NAME}.versioned.kicad_sch $@ ${PANEL_DIR}
+	pcbdraw --silent $@ --dpi 600 panel.brd-top.png
+	pcbdraw --silent $@ --dpi 600 --back panel.brd-bot.png
 
 clean:
 	rm -f $(foreach EXT,$(VERSIONED_EXT),${NAME}.versioned.$(EXT))
-	rm -f ${NAME}.sch.pdf ${NAME}.brd-top.png ${NAME}.brd-bot.png ${NAME}.brd-top.svg ${NAME}.brd-bot.svg ${NAME}.versioned.xml ${NAME}.bom.csv
+	rm -f ${NAME}.sch.pdf ${NAME}.brd-top.png ${NAME}.brd-bot.png ${NAME}.versioned.xml ${NAME}.bom.csv
 	rm -f ${NAME}.versioned.kicad_prl ${NAME}.versioned.kicad_pro-bak ${NAME}.versioned.xml ${NAME}.versioned.csv
 	rm -f ${IBOM}
 	rm -rf ${FABRICATION_DIR}
-	rm -f panel.versioned.json panel.kicad_pcb panel.kicad_pro panel.brd-top.svg panel.brd-bot.svg panel.brd-top.png panel.brd-bot.png
+	rm -f panel.kicad_pcb panel.kicad_pro 
 	rm -rf ${PANEL_DIR}

README.md

@@ -1,7 +1,152 @@
-these are the hardware design files for **insert project name here**.
+The USB micro-B and C cable tester identifies capabilities supported by USB cables and deduces their purpose.
+It helps figuring out if a USB cable is for charging or to transfer data, and at which speed.
+It supports type A to micro-B, A to C, and C to C USB cables.
 
-purpose
-=======
+<img src="picture/front.webp" title="front" height="250"/>
+<img src="picture/back.webp" title="back" height="250"/>
 
 usage
 =====
+
+- ensure the tester has a non-empty battery in the CR2032/2025 slot, or is externally powered through the USB power port
+- plug one end of the cable in one of the host ports
+- plug the other end of the cable in one of the devices ports
+- when using a battery, press on the BAT ON button
+- the tester will identify the cable's capabilities, on the left side
+- the tester will then show the cable's purpose, on the right side
+
+Once I know it's purpose, I mark the cables with a letter:
+
+- USB A to micro-B only with ground and VBUS wires, limiting power transfer to 0.5 since they can't indicate battery charge: **P**
+
+<img src="picture/a-b-p.webp" width="300"/>
+
+- USB A to micro-B, with data line shorted internally to indicate 1.5A battery charge (even when not sure the host supports it): **C**
+
+<img src="picture/a-b-c.webp" width="300"/>
+
+- USB A to micro-B with data wires, but error prone since not shielded (sufficient for low speed): **D**
+
+<img src="picture/a-b-d.webp" width="300"/>
+
+- USB A to micro-B with shielded data wires (good for high speed): **S**
+
+<img src="picture/a-b-s.webp" width="300"/>
+
+- USB A to C without data lines but battery charge indication: **C**
+
+<img src="picture/a-c-c.webp" width="300"/>
+
+- USB A to C with unshielded data lines: **D**
+
+<img src="picture/a-c-d.webp" width="300"/>
+
+- USB A to C with SuperSpeed data lines, and shielded: **3**
+
+<img src="picture/a-c-3.webp" width="300"/>
+
+- USB A to C with SuperSpeed data lines, but unshielded (thus faulty): **D**
+
+<img src="picture/a-c-sd.webp" width="300"/>
+
+- USB C to C with shielded data lines: **S**
+
+<img src="picture/c-c-s.webp" width="300"/>
+
+- USB C to C with electronic marking allowing 5A charging: **C**
+
+<img src="picture/c-c-c.webp" width="300"/>
+
+- USB C to C with all features: **F**
+
+<img src="picture/c-c-f.webp" width="300"/>
+
+The tester can detect electronically marked C to C cables.
+Often they are present (and required) in cables allowing 5A/100W charging.
+But to be sure, one should read the capabilities from the chip, which is not supported by the tester.
+Full Feature C to C cable also require electronical marking, but could only support 3A charging.
+Because of that the 3A and 5A indicators are on at the same time (when the marking can be just for the features).
+
+To understand further the capabilities and purpose of a cable, I recommend reading the USB specification, mainly the one for the [type-C connector](https://www.usb.org/document-library/usb-type-cr-cable-and-connector-specification-release-23).
+
+report
+------
+
+There is a UART output on the debug port.
+The analysis of the capabilities to the purpose is periodically output on it.
+You can connect to it and view it using the 115200 8N1 baud rate.
+
+firmware
+--------
+
+You can flash or update the firmware using the SWD signals on the debug port, of also use the UART signals and the bootloader.
+To start the bootloader, press and hold the BL button while shortly pressing the RST button.
+You can then use [stm32flash](https://github.com/stm32duino/stm32flash):
+
+~~~
+stm32flash -w binray.hex -v /dev/ttyACM0
+~~~
+
+The compiled binary is available in the release archives.
+The source code of the firmware is in the `firmware` folder.
+
+design choice
+=============
+
+features
+--------
+
+do:
+
+- USB micro-B: still wide-spread and popular for charging devices
+- USB type-A: still the de-facto host plug
+- USB type-C: becoming the standard for battery operated devices
+- C to C: often used for high power charging of phones and laptops
+- battery operated: it's a very simple device, and this avoids needing to require external power
+- power port: in case you have no battery or it runs out
+- USB 3.0: because it is hard to identify if C-C cable support SuperSpeed
+- purpose: deduce from capabilities for users not knowledgable in USB cables
+
+don't:
+
+- small: no need to build it as compact as possible
+- A to micro-B 3.0: the connectors that support it are obvious, and it's rare they are used for anything else than Super-Speed transfer (plus they are less common or problematic)
+- Power Delivery capabilities: this requires complex host software communicating with the eMarker chip in the cable
+- OTG: even if detecting this functionality is easy, micro-B OTG adapters are not popular anymore
+- impedance: only the presence of wires is tester, not their impedance
+
+mode of operation
+-----------------
+
+Most of the tests just verify if the wires corresponding to capabilities are present in the cable.
+Some additional tests verify the resistances in the plugs.
+For more details, check the schematic, and refer to [type-C specification](https://www.usb.org/document-library/usb-type-cr-cable-and-connector-specification-release-23).
+
+The left side identifies the capabilities.
+Based on that, a micro-controller (MCU) will map the combination into a purpose on the right side.
+The left side is independent of the MCU and right side.
+
+limitation
+----------
+
+The tester does not:
+
+- verify the resistance of wires, particularly the power ones
+- verify the impedance of wires, particularly the differential ones
+- verify if the shield(s) is more than just a wire
+- read out capabilities from electronically marked cables
+- guarantee USB cable compliance or conformity, as this is [very complex](https://www.usb.org/documents?search=&category%5B%5D=49&type%5B%5D=56&tid_2%5B%5D=41&items_per_page=50)
+
+You can short the two pads marked BAT ON next to the battery with a solder blob.
+This will always power the board and does not require you to press on the BAT ON button to do the test, like when powering through the USB POWER port.
+But this will continuously drain 0.7 mA, emptying a CR2032 coin cell in 24 days.
+
+alternatives
+------------
+
+- [USB micro-B cable tester](https://www.cuvoodoo.info/cuvoodoo-gadget-micro-usb-cable-tester-v2/): only does micro-B cables
+- [USB A-C cable tester](https://www.cuvoodoo.info/cuvoodoo-gadget-usb-a-to-usb-c-cable-tester-v1/): only does USB type A to type C cables
+- [USB C-C cable tester](https://www.cuvoodoo.info/cuvoodoo-gadget-usb-c-cable-tester-v2/): only does USB type C to type C cables
+- [DT3 Data Cable Detection Board](https://www.aliexpress.com/item/1005006302832038.html): does not check shield, battery charging, USB 3.0
+- [USB Cable Checker 2](https://www.tindie.com/products/bittradeone/usb-cable-checker-2-assembled/): too complex and expensive
+- [USB Cable Tester](https://github.com/alvarop/usb_c_cable_tester): only for USB-C and you have to understand and interpret the signals

firmware/.gitignore

@@ -0,0 +1,7 @@
+*.bin
+*.hex
+*.elf
+*.ld
+*.o
+*.d
+*.bak

firmware/.gitmodules

@@ -0,0 +1,3 @@
+[submodule "libopencm3"]
+	path = libopencm3
+	url = https://github.com/libopencm3/libopencm3

firmware/LICENSE.txt

@@ -0,0 +1,674 @@
+                    GNU GENERAL PUBLIC LICENSE
+                       Version 3, 29 June 2007
+
+ Copyright (C) 2007 Free Software Foundation, Inc. <https://fsf.org/>
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
+                            Preamble
+
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+software and other kinds of works.
+
+  The licenses for most software and other practical works are designed
+to take away your freedom to share and change the works.  By contrast,
+the GNU General Public License is intended to guarantee your freedom to
+share and change all versions of a program--to make sure it remains free
+software for all its users.  We, the Free Software Foundation, use the
+GNU General Public License for most of our software; it applies also to
+any other work released this way by its authors.  You can apply it to
+your programs, too.
+
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+price.  Our General Public Licenses are designed to make sure that you
+have the freedom to distribute copies of free software (and charge for
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firmware/Makefile

@@ -0,0 +1,42 @@
+DEVICE = stm32f030c8t6
+OPENCM3_DIR =./libopencm3
+OBJS += main.o
+
+CFLAGS += -Os -ggdb3 -specs=nosys.specs
+CPPFLAGS += -MD
+LDFLAGS += -static -nostartfiles -specs=nosys.specs
+LDLIBS += -Wl,--start-group -lc -lgcc -lnosys -Wl,--end-group
+
+OOCD ?= openocd
+OOCD_INTERFACE ?= cmsis-dap
+OOCD_TARGET ?= stm32f0x
+
+include $(OPENCM3_DIR)/mk/genlink-config.mk
+include $(OPENCM3_DIR)/mk/gcc-config.mk
+
+.PHONY: clean all
+
+all: binary.elf binary.hex
+
+clean:
+	$(Q)$(RM) -rf binary.* *.o
+
+bl: binary.hex
+	stm32flash -w $< -v /dev/ttyACM0
+
+flash: binary.elf
+	$(OOCD) -f interface/$(OOCD_INTERFACE).cfg \
+		-f target/$(OOCD_TARGET).cfg \
+		-c "program $< verify reset exit"
+
+debug: binary.elf
+	$(GDB) --eval-command='target remote | $(OOCD) --file interface/$(OOCD_INTERFACE).cfg --command "transport select swd" --file target/$(OOCD_TARGET).cfg --command "gdb_port pipe; log_output /dev/null; init"' $<
+
+include $(OPENCM3_DIR)/mk/genlink-rules.mk
+include $(OPENCM3_DIR)/mk/gcc-rules.mk
+
+$(OPENCM3_DIR)/lib/lib$(LIBNAME).a:
+ifeq (,$(wildcard $@))
+	$(warning $(LIBNAME).a not found, attempting to rebuild in $(OPENCM3_DIR))
+	$(MAKE) -C $(OPENCM3_DIR)
+endif

firmware/libopencm3

@@ -0,0 +1 @@
+Subproject commit bb4c5d7324554fe7a3137bfbcf3b5200ee2648fa

firmware/main.c

@@ -0,0 +1,745 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later
+ * Copyright 2024 King Kévin <kingkevin@cuvoodoo.info>
+ */
+#include <libopencm3/stm32/rcc.h>
+#include <libopencm3/stm32/gpio.h>
+#include <libopencm3/stm32/usart.h>
+#include <libopencm3/stm32/timer.h>
+#include <libopencm3/stm32/adc.h> // ADC utilities
+#include <libopencm3/cm3/nvic.h>
+
+#include <stdio.h>
+#include <errno.h>
+#include <sys/stat.h>
+
+// get the length of an array
+#define LENGTH(x) (sizeof(x) / sizeof((x)[0]))
+// print debug messages
+#define DEBUG (false)
+// duration to wait for pull-up/down (in cycles)
+#define PULL_DURATION (100U)
+
+enum io_name {
+	// inputs
+	GNDA, // on host side, pulled high
+	GNDC, // on host side, pulled high
+	VBUSB, // on device side, pulled low
+	VBUSC, // on device side, pulled low
+	HDM, // pulled high when no wire, pulled low when wire
+	HDP, // pulled low when no wire, high when wire
+	DDM, // pulled low when not shorted, high when shorted
+	SSP, // 3V3 on A when SS wires present, sources LED, not pulled
+	SSM, // GND on A when SS wires present, sinks LED, not pulled
+	SS1, // GND on C when SS wires present, sinks LED, not pulled
+	SS2, // GND on C when SS wires present, sinks LED, not pulled
+	HCC1, // pulled high
+	HCC2, // pulled high
+	DCC1, // pull high when CC wire present, weakly pulled low
+	DCC2, // pull high when CC wire present, weakly pulled low
+	SBU, // GND on C when SBU wires present, sinks LED, not pulled
+	HSH, // GND when host-C present, pulled high
+	DSH, // GND when device-C present, sinks LED, no pulled
+	BSH, // pull high when *-B shield present, weakly pulled low (to cable ground)
+	// button input
+	BUTTON,
+	// outputs
+	LEDX,
+	LEDY,
+	LEDZ,
+	LED1,
+	LED2,
+	LED3,
+	LED4,
+	IO_MAX
+};
+
+static const uint32_t io_port[IO_MAX] = {
+	[GNDA] = GPIOC,
+	[GNDC] = GPIOC,
+	[VBUSB] = GPIOB,
+	[VBUSC] = GPIOB,
+	[HDM] = GPIOF,
+	[HDP] = GPIOF,
+	[DDM] = GPIOC,
+	[SSP] = GPIOB,
+	[SSM] = GPIOB,
+	[SS1] = GPIOB,
+	[SS2] = GPIOB,
+	[HCC1] = GPIOA,
+	[HCC2] = GPIOA,
+	[DCC1] = GPIOA,
+	[DCC2] = GPIOA,
+	[SBU] = GPIOB,
+	[HSH] = GPIOA,
+	[DSH] = GPIOA,
+	[BSH] = GPIOA,
+	[BUTTON] = GPIOB,
+	[LEDX] = GPIOB,
+	[LEDY] = GPIOB,
+	[LEDZ] = GPIOB,
+	[LED1] = GPIOB,
+	[LED2] = GPIOB,
+	[LED3] = GPIOB,
+	[LED4] = GPIOB,
+};
+
+static const uint16_t io_pin[IO_MAX] = {
+	[GNDA] = GPIO13,
+	[GNDC] = GPIO14,
+	[VBUSB] = GPIO8,
+	[VBUSC] = GPIO9,
+	[HDM] = GPIO1,
+	[HDP] = GPIO0,
+	[DDM] = GPIO15,
+	[SSP] = GPIO0,
+	[SSM] = GPIO1,
+	[SS1] = GPIO2,
+	[SS2] = GPIO10,
+	[HCC1] = GPIO3,
+	[HCC2] = GPIO4,
+	[DCC1] = GPIO2,
+	[DCC2] = GPIO1,
+	[SBU] = GPIO11,
+	[HSH] = GPIO7,
+	[DSH] = GPIO6,
+	[BSH] = GPIO5,
+	[BUTTON] = GPIO7,
+	[LEDX] = GPIO5,
+	[LEDY] = GPIO4,
+	[LEDZ] = GPIO3,
+	[LED1] = GPIO12,
+	[LED2] = GPIO13,
+	[LED3] = GPIO14,
+	[LED4] = GPIO15,
+};
+
+// if we should do a pull test
+// the capability tests use current to power LEDs, we need to check using voltage
+static const uint16_t io_pull[BUTTON] = {
+	[GNDA] = false,
+	[GNDC] = false,
+	[VBUSB] = false,
+	[VBUSC] = false,
+	[HDM] = false,
+	[HDP] = false,
+	[DDM] = false,
+	[SSP] = true, // capability current test
+	[SSM] = true, // capability current test
+	[SS1] = true, // capability current test
+	[SS2] = true, // capability current test
+	[HCC1] = false,
+	[HCC2] = false,
+	[DCC1] = false,
+	[DCC2] = false,
+	[SBU] = true, // capability current test
+	[HSH] = false,
+	[DSH] = true, // capability current test
+	[BSH] = false,
+	// LEDs are not pulls
+};
+
+static bool io_pn[BUTTON] = {false}; // if up when not pulled
+static bool io_pu[BUTTON] = {false}; // if up when pulled up
+static bool io_pd[BUTTON] = {false}; // if up when pulled down
+
+uint16_t ledx = 0; // which LEDs to set on row X
+uint16_t ledy = 0; // which LEDs to set on row Y
+uint16_t ledz = 0; // which LEDs to set on row Z
+
+// voltages to convert
+const uint8_t channels[] = { // must be ordered by number
+	0, // VCC, PA0, ADC_IN0
+	1, // DCC2, PA1, ADC_IN1
+	2, // DCC1, PA2, ADC_IN2
+	3, // HCC1, PA3, ADC_IN3
+	4, // HCC2, PA4, ADC_IN4
+	ADC_CHANNEL_VREF, // internal voltage reference
+};
+
+enum fault {
+	FAULT_VBUS_NOT_GND,
+	FAULT_GND_NOT_VBUS,
+	FAULT_DM_CONNECT,
+	FAULT_HOST_DATA_PULLED,
+	FAULT_DATA_NOT_GND,
+	FAULT_DATA_NOT_VBUS,
+	FAULT_SS_NOT_GND,
+	FAULT_SS_NOT_VBUS,
+	FAULT_SS_NOT_SHIELD,
+	FAULT_SS_NOT_DATA,
+	FAULT_GND_DRAIN,
+	FAULT_CC_NOT_DC,
+	FAULT_DC_NOT_CCRP,
+	FAULT_CC_NOT_CC,
+	FAULT_SBU_NOT_HC,
+	FAULT_SBU_NOT_DC,
+	FAULT_RA_NOT_HA,
+	FAULT_RA_NOT_DC,
+	FAULT_AC_NOT_RP,
+	FAULT_RP_NOT_AC,
+	FAULT_RD_NOT_DB,
+	FAULT_MAX
+};
+
+static const char* faults[FAULT_MAX] = {
+	[FAULT_VBUS_NOT_GND] = "VBUS present, but GND missing",
+	[FAULT_GND_NOT_VBUS] = "GND present, but VBUS missing",
+	[FAULT_DM_CONNECT] = "host and device D- not inter-connected",
+	[FAULT_HOST_DATA_PULLED] = "host data lines are not floating",
+	[FAULT_DATA_NOT_GND] = "data lines present, but GND missing",
+	[FAULT_DATA_NOT_VBUS] = "data lines present, but VBUS missing",
+	[FAULT_SS_NOT_GND] = "SuperSpeed data lines present, but GND missing",
+	[FAULT_SS_NOT_VBUS] = "SuperSpeed data lines present, but VBUS missing",
+	[FAULT_SS_NOT_SHIELD] = "SuperSpeed data lines present, but shield missing",
+	[FAULT_SS_NOT_DATA] = "SuperSpeed data lines present, but USB 2.0 data lines missing",
+	[FAULT_GND_DRAIN] = "GND_DRAIN not connected to ground",
+	[FAULT_CC_NOT_DC] = "Rp/CC line present, but device C missing",
+	[FAULT_DC_NOT_CCRP] = "device C present, but Rp/CC line missing",
+	[FAULT_CC_NOT_CC] = "C-C cable, but CC line missing",
+	[FAULT_SBU_NOT_HC] = "SBU present, but host C missing",
+	[FAULT_SBU_NOT_DC] = "SBU present, but device C missing",
+	[FAULT_RA_NOT_HA] = "Ra detected, but host A missing",
+	[FAULT_RA_NOT_DC] = "Ra detected, but device C missing",
+	[FAULT_AC_NOT_RP] = "A-C cable, but Rp missing",
+	[FAULT_RP_NOT_AC] = "Rp detected, but not A-C cable",
+	[FAULT_RD_NOT_DB] = "Rd detected, but not C-microB cable",
+};
+
+enum cc_rx {
+	R_UNKNOWN, // everything else
+	R_OPEN, // pulled by board, no resistor in cable, no CC wire
+	R_5K1, // pulled by board, no resistor in cable, CC wire
+	RA_1K, // Ra in cable to indicate eMarker
+	RD_5K1, // 5.1k pull down Rd resistor in host C to indicate device
+	RP_56K, // 56k pull up Rp resistor in device C to indicate host current capable of 0.5-0.8A
+	RP_22K, // 22k pull up Rp resistor in device C to indicate host current capable of 1.5A
+	RP_10K, // 10k pull up Rp resistor in device C to indicate host current capable of 3.0A
+	R_MAX,
+};
+
+static const char* cc_rx_str[R_MAX] = {
+	[R_UNKNOWN] = "?",
+	[R_OPEN] = "open",
+	[R_5K1] = "C-C",
+	[RA_1K] = "Ra",
+	[RD_5K1] = "Rd",
+	[RP_56K] = "Rp 56k",
+	[RP_22K] = "Rp 22k",
+	[RP_10K] = "Rp 10k",
+};
+
+// measured and set by meas_rx
+static enum cc_rx cc_r[4]; // HCC1, HCC2, DCC1, DCC2
+
+__attribute__((weak)) int _read(int file, char *ptr, int len){ return -1; }
+int _close(int file){ return -1; }
+int _fstat(int file, struct stat *st){ st->st_mode = S_IFCHR; return 0; }
+int _isatty(int file){ return 1; }
+int _lseek(int file, int ptr, int dir){ return 0; }
+int _getpid(){ return -1; }
+int _kill(int pid, int sig){ return -1; }
+
+int _write(int file, char *ptr, int len)
+{
+	int i;
+
+	if (file == 1) {
+		for (i = 0; i < len; i++)
+			usart_send_blocking(USART1, ptr[i]);
+		return i;
+	}
+
+	errno = EIO;
+	return -1;
+}
+
+static void usart_setup(void)
+{
+	// enable clocks for USART
+	rcc_periph_clock_enable(RCC_USART1);
+	// setup GPIO pins for USART transmit
+	gpio_mode_setup(GPIOA, GPIO_MODE_AF, GPIO_PUPD_NONE, GPIO9);
+	// setup USART TX pin as alternate function
+	gpio_set_af(GPIOA, GPIO_AF1, GPIO9);
+
+	// setup USART parameters
+	usart_set_baudrate(USART1, 115200);
+	usart_set_databits(USART1, 8);
+	usart_set_parity(USART1, USART_PARITY_NONE);
+	usart_set_stopbits(USART1, USART_CR2_STOPBITS_1);
+	usart_set_mode(USART1, USART_MODE_TX);
+	usart_set_flow_control(USART1, USART_FLOWCONTROL_NONE);
+	usart_enable(USART1);
+}
+
+static void gpio_setup(void)
+{
+	// enable GPIO clock for inputs and LEDs
+	rcc_periph_clock_enable(RCC_GPIOA);
+	rcc_periph_clock_enable(RCC_GPIOB);
+	rcc_periph_clock_enable(RCC_GPIOC);
+	rcc_periph_clock_enable(RCC_GPIOF);
+
+	// ADC to measure Rp
+	gpio_mode_setup(GPIOA, GPIO_MODE_ANALOG, GPIO_PUPD_NONE, GPIO0); // Vcc analog input
+	rcc_periph_clock_enable(RCC_ADC1); // enable clock for ADC domain
+	adc_power_off(ADC1); // switch off ADC while configuring it
+	adc_set_clk_source(ADC1, ADC_CLKSOURCE_ADC);
+	adc_set_right_aligned(ADC1); // ensure it is right aligned to get the actual value in the 16-bit register
+	adc_disable_external_trigger_regular(ADC1);
+	adc_enable_vrefint(); // enable internal voltage reference
+	adc_set_operation_mode(ADC1, ADC_MODE_SCAN); // use scan mode do be able to go to next discontinuous subgroup of the regular sequence
+	adc_enable_discontinuous_mode(ADC1); // use discontinuous mode (to go through all channels of the group, one after another)
+	adc_set_single_conversion_mode(ADC1); // ensure continuous mode is not used (that's not the same as discontinuous)
+	adc_set_sample_time_on_all_channels(ADC1, ADC_SMPTIME_071DOT5);
+	adc_set_regular_sequence(ADC1, LENGTH(channels), (uint8_t*)channels); // set channel to convert
+	adc_set_resolution(ADC1, ADC_RESOLUTION_12BIT);
+	adc_disable_analog_watchdog(ADC1);
+	adc_calibrate(ADC1);
+	adc_power_on(ADC1); // switch on ADC
+
+	// setup GPIO pin for inputs
+	for (uint8_t i = 0; i < LEDX; i++) {
+		gpio_mode_setup(io_port[i], GPIO_MODE_INPUT, GPIO_PUPD_NONE, io_pin[i]);
+	}
+
+	// setup GPIO pin for LEDs
+	for (uint8_t i = LEDX; i < IO_MAX; i++) {
+		gpio_clear(io_port[i], io_pin[i]); // switch off LED
+		gpio_mode_setup(io_port[i], GPIO_MODE_OUTPUT, GPIO_PUPD_NONE, io_pin[i]); // set as output
+	}
+
+	// test LEDs
+	gpio_clear(io_port[LEDX], io_pin[LEDX] | io_pin[LEDY] | io_pin[LEDZ]); // disable all rows
+	gpio_clear(io_port[LED1], io_pin[LED1] | io_pin[LED2] | io_pin[LED3] | io_pin[LED4]); // enable all columns
+	gpio_set(io_port[LEDX], io_pin[LEDX]); // enable first row
+	for (volatile uint32_t i = 0; i < 20000; i++);
+	gpio_clear(io_port[LEDX], io_pin[LEDX]); // disable first row
+	gpio_set(io_port[LEDY], io_pin[LEDY]); // enable second row
+	for (volatile uint32_t i = 0; i < 20000; i++);
+	gpio_clear(io_port[LEDY], io_pin[LEDY]); // disable second row
+	gpio_set(io_port[LEDZ], io_pin[LEDZ]); // enable second row
+	for (volatile uint32_t i = 0; i < 20000; i++);
+	gpio_clear(io_port[LEDZ], io_pin[LEDZ]); // disable third row
+}
+
+static void timer_setup(void)
+{
+	// enable timer for LED matrix
+	rcc_periph_clock_enable(RCC_TIM14); // enable clock for timer peripheral
+	rcc_periph_reset_pulse(RST_TIM14); // reset timer state
+	timer_set_mode(TIM14, TIM_CR1_CKD_CK_INT, TIM_CR1_CMS_EDGE, TIM_CR1_DIR_UP); // set timer mode, use undivided timer clock,edge alignment (simple count), and count up
+	timer_set_prescaler(TIM14, 1); // set lowest speed to not flicker
+	timer_set_period(TIM14, 15000); // hand tuned
+	timer_clear_flag(TIM14, TIM_SR_UIF); // clear flag