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USB PD chip evaluation configuration

This board configuration implements a USB Power Delivery TCPM in order to evaluate various TCPC chips. The code tries to follow the preliminary USB PD interface standard but for TCPC chip implementing proprietary I2C protocol, a new TCPM file can be implemented as explained in the Updating the code section below.

Building

ChromiumOS chroot

All the following instructions have been verified in a ChromiumOS chroot. You can find how to set one up on the Chromium development wiki: http://dev.chromium.org/chromium-os/quick-start-guide

Build the TCPM code

cd src/platform/ec

make BOARD=pdeval-stm32f072

Updating the code

TCPC Communication code

Please duplicate driver/tcpm/tcpci.c into driver/tcpm/##chip#name##.c. Then update the control logic through I2C there.

In order for your new code to compile, you need to update driver/build.mk with the new file : driver-$(CONFIG_USB_PD_TCPM_##CHIP#NAME##)+=tcpm/##chip#name##.o then document the new CONFIG_USB_PD_TCPM_ variable in the include/config.h file and define it in the board configuration in board/pdeval-stm32f072/board.h.

Board configuration

In board/pdeval-stm32f072/board.h, you can update CONFIG_USB_PD_PORT_COUNT to the actual number of ports on your board. You also need to create/delete the corresponding PD_Cx tasks in board/pdeval-stm32f072/ec.tasklist.

By default, the firmware is using I2C1 with SCL/SDA on pins PB6 and PB7, running with a 100kHz clock, and tries to talk to TCPCs at i2c slave addresses 0x9c and 0x9e. To change the pins or speed, you need to edit i2c_ports in board/pdeval-stm32f072/board.c, update I2C_PORT_TCPC in board/pdeval-stm32f072/board.h with the right controller number, and change the pin mux in board/pdeval-stm32f072/gpio.inc. To change TCPC i2c slave addresses, update TCPC1_I2C_ADDR and TCPC2_I2C_ADDR in board/pdeval-stm32f072/board.h.

The I2C bus needs pull-up resistors on SCL/SDA. If your setup doesn't have external pull-ups on those lines, you can activate the chip internal pull-ups (but they are a bit weak for I2C) by editing board/pdeval-stm32f072/gpio.inc and updating the alternate mode configuration flags with GPIO_PULL_UP e.g. : ALTERNATE(PIN_MASK(B, 0x00c0), 1, MODULE_I2C, GPIO_PULL_UP) /* I2C MASTER:PB6/7 */

An interrupt line, PA1, is configured to be used for the TCPC to get the attention of the TCPM. The GPIO is configured to trigger an interrupt on the falling edge and will call tcpc_alert(), which must be implemented in driver/tcpm/.c, and should determine the cause of the interrupt and take action. The GPIO can be changed in board/pdeval-stm32f072/gpio.inc.

Flashing and Running

Flashing the firmware binary

To flash through JTAG with OpenOCD, you can just run:

sudo make flash BOARD=pdeval-stm32f072

Note: you need to do that with your USB mini-B cable is connected to the USB ST-LINK plug on the discovery board.

Connecting to the firmware console

Connect a USB cable to the USB USER mini-B receptacle on the board. lsusb should show you a device with the following ID : 18d1:500f

You can get a console over USB by issuing the following command on a Linux computer:

echo '18d1 500f' | sudo tee /sys/bus/usb-serial/drivers/generic/new_id

Testing

Currently, the TCPM is expecting to have a GPIO to detect VBUS, but to minimize the HW setup with the discovery board the alternative is to fake VBUS detection using either the USER button on the discovery board, or the vbus console command, both of which toggle the state of VBUS detected. For example, to make get a PD contract with a power adapter, plug in the adapter and then toggle VBUS on. When a PD contract above 6V is made, LED5 on the discovery board will light. To disconnect, toggle VBUS off.

EC command line commands

help List all available EC console commands
vbus Toggle VBUS on/off
pd <port> state Print PD protocol state information
pd <port> swap data Request data role swap on port
pd <port> swap power Request power role swap on port
i2cscan Scan i2c bus for any responsive devices
i2cxfer Perform an i2c transaction

On the console, you will the PD state machine transitioning through its states with traces like C0 st5. You can always the human readable name of the current state by doing pd 0 state returning something like : Port C0 CC1, Ena - Role: SNK-UFP State: SNK_DISCOVERY, Flags: 0x0608 else the numbering of the state is defined in include/usb_pd.h by the PD_STATE_ constants. It should be by default :

[0] DISABLED
[1] SUSPENDED
[2] SNK_DISCONNECTED
[3] SNK_DISCONNECTED_DEBOUNCE
[4] SNK_HARD_RESET_RECOVER
[5] SNK_DISCOVERY
[6] SNK_REQUESTED
[7] SNK_TRANSITION
[8] SNK_READY
[9] SNK_SWAP_INIT
[10] SNK_SWAP_SNK_DISABLE
[11] SNK_SWAP_SRC_DISABLE
[12] SNK_SWAP_STANDBY
[13] SNK_SWAP_COMPLETE
[14] SRC_DISCONNECTED
[15] SRC_DISCONNECTED_DEBOUNCE
[16] SRC_ACCESSORY
[17] SRC_HARD_RESET_RECOVER
[18] SRC_STARTUP
[19] SRC_DISCOVERY
[20] SRC_NEGOCIATE
[21] SRC_ACCEPTED
[22] SRC_POWERED
[23] SRC_TRANSITION
[24] SRC_READY
[25] SRC_GET_SINK_CAP
[26] DR_SWAP
[27] SRC_SWAP_INIT
[28] SRC_SWAP_SNK_DISABLE
[29] SRC_SWAP_SRC_DISABLE
[30] SRC_SWAP_STANDBY
[31] SOFT_RESET
[32] HARD_RESET_SEND
[33] HARD_RESET_EXECUTE
[34] BIST_RX
[35] BIST_TX

Known Issues

This doc is not finished yet ...
You might need a ChromeOS chroot ...

Troubleshooting

OpenOCD is not finding the device.
1. Check that your USB mini-B cable is connected to the USB ST-LINK plug on the discovery board.
2. What color is the LD1 LED on the board ?
On the I2C bus, SDA/SCL lines are staying always low
1. You might be missing some pull-up resistors on the bus.
2. Check the Board configuration section if you cannot add external pull-ups.
You got black smoke
1. Time to buy a new one.

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