Describe how PDOs are formatted

Each field's name and meaning is listed now, and the unsupported types
are no longer listed as if they are supported.  As always, I'd like to
support variable and battery PDOs, but I need hardware that sends them
to add such support.

docs/console_config.md

@@ -198,7 +198,9 @@ Usage: `get_source_cap`
 
 Prints the capabilities advertised by the Power Delivery source.  Each
 capability is represented by a Power Data Object (PDO), printed in the format
-listed in the PDO Format section below.
+listed in the PDO Format section below.  If there are no capabilities, e.g.
+when the source does not support USB Power Delivery, `No Source_Capabilities`
+is printed instead.
 
 ## Configuration Format
 
@@ -236,13 +238,13 @@ this configuration object:
 
 The `v` field holds the fixed voltage of the configuration object, in volts.
 The field's value is a floating-point decimal number, followed by a space and a
-capital V.  For example: `20.00 V`
+capital V.  For example: `20.00 V`.
 
 ### i
 
 The `i` field holds the fixed current of the configuration object, in amperes.
 The field's value is a floating-point decimal number, followed by a space and a
-capital A.  For example: `2.25 A`
+capital A.  For example: `2.25 A`.
 
 ## PDO Format
 
@@ -250,15 +252,61 @@ When a list of PDOs is printed, each PDO is numbered with a line as follows:
 
     PDO n: type
 
-`n` is the index of the PDO.  `type` is one of `fixed`, `variable`, `battery`,
-or the entire PDO represented as a 32-bit hexadecimal number if the type is
-unknown.  If `type` is not a hexadecimal number, the rest of the PDO is printed
-as a list of fields, one per line, each indented by a single ASCII tab
-character.  Each field is of the format:
+`n` is the index of the PDO.  `type` is one of `fixed`, or the entire PDO
+represented as a 32-bit hexadecimal number if the type is unknown.  If `type`
+is not a hexadecimal number, the rest of the PDO is printed as a list of
+fields, one per line, each indented by a single ASCII tab character.  Each
+field is of the format:
 
     name: value
 
-**TODO**: describe exactly how each type of PDO is printed.
+### Source Fixed Supply PDO Fields
+
+This section describes how Source Fixed Supply PDOs (type `fixed`) are printed.
+For more information about the meaning of each field, see the USB Power
+Delivery Specification, Revision 2.0, Version 1.3, section 6.4.1.2.3.
+
+#### dual_role_pwr
+
+The `dual_role_pwr` field holds the value of the PDO's Dual-Role Power bit
+(B29).  If this field is not present, its value shall be assumed 0.
+
+#### usb_suspend
+
+The `usb_suspend` field holds the value of the PDO's USB Suspend Supported bit
+(B28).  If this field is not present, its value shall be assumed 0.
+
+#### unconstrained_pwr
+
+The `unconstrained_pwr` field holds the value of the PDO's Unconstrained Power
+bit (B27).  If this field is not present, its value shall be assumed 0.
+
+#### usb_comms
+
+The `usb_comms` field holds the value of the PDO's USB Communications Capable
+bit (B26).  If this field is not present, its value shall be assumed 0.
+
+#### dual_role_data
+
+The `dual_role_data` field holds the value of the PDO's Dual-Role Data bit
+(B25).  If this field is not present, its value shall be assumed 0.
+
+#### peak_i
+
+The `peak_i` field holds the value of the PDO's Peak Current field (B21-20), in
+decimal.  If this field is not present, its value shall be assumed 0.
+
+#### v
+
+The `v` field holds the value of the PDO's Voltage field (B19-10), in volts.
+The field's value is a floating-point decimal number, followed by a space and a
+capital V.  For example: `20.00 V`.
+
+#### i
+
+The `i` field holds the value of the PDO's Maximum Current field (B9-0), in
+amperes.  The field's value is a floating-point decimal number, followed by a
+space and a capital A.  For example: `2.25 A`.
 
 ## USB Descriptors