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Specifications of Morphy USB-IO

Hardware characteristics of I/O ports

Hardware characteristics of the I/O port pins of Morphy USB-IO is summarized as follows. The information is taken from Cypress CY7C63001A datasheet, which is the core of the device, and the source program of the Morphy USB-IO firmware. There may be some errors, especially in timing (I have no oscilloscope, so all time values are estimated from the source.)

I/O port configuration

Morphy USB-IO has 12 I/O pins that are controlled by host program. They are divided into two groups: Port #0 and Port #1. Port #0 consists of 8 bits (pins) and Port #1 4 bits (pins.) Each I/O pins may be used as input or output independently from other pins. Port #0 pins and Port #1 pins differ in many ways.

Equivalent schematics of an I/O port

Cy7C63001A has carefully designed, complex circuit for I/O pins. Several aspects of the circuit can be configured by firmware. When I look at the schemata shown on the datasheet, I didn't understand how I can configure a pin to either input or output.

After checking the firmware, I found that, in Morphy USB-IO, a pin can be considered to have a circuit roughly equivalent to a schematics specified in the following figure.

Equivalent schematics of an I/O port

The point is, an output buffer is not three-state controlled but is a combination of open collector (open drain) and a pull-up register. There is no explicit way to select input or output. Instead, when viewed as an output, a pin always output a value stored in the corresponding register, and, when viewed as an input, the firmware sees the wired-and of the external signal and the internal output register. That is, when a pin is to operate as an input, the corresponding output register must be set to a one (HIGH level), since the value actually read will be masked otherwise.

You can use the Morphy USB-IO I/O pins as follows:

Note that, since each pin is internally pulled-up, you cannot put an I/O pin into high impedance (Z) in Morphy USB-IO, although the CY7C63001A chip itself has the feature. This limitation comes from the firmware.

Drive current

Pins on Port #0 and Port #1 have different maximum drive current. Port #0 is for small load and each pin on it can only sink up to 1.5mA at low level output. Port #1 is for heavy load and each pin can sink up to 8mA even in worst case. Leak current at high level output on both ports are limited to those supplied by the internal pull-up registers, so large current is unavailable. If you want to drive LEDs, for example, you should use pins on Port #1 in active-low.

Note that the internal pull-up registers on both ports are specified as between 8kΩ and 24kΩ.

Firmware Versions

There are two versions of Morphy USB-IO firmware. They are ver. 1 and ver. 2. Ver. 2 is latest, as far as I know.

Note that firmware version is independent from PCB versions. In particular, the PCB currently under distribution is marked as ver. 4.

Behaviour as USB device

The device

The host PC recognizes Morphy USB-IO as a low speed USB device of HID class. It doesn't, however, belong to any particular HID device type, so operating systems will report it as something like "other" HID device. For example, Windows 98 reports it as "HID compatible device."

Morphy USB-IO consists of, in USB's sayings, one configuration, one interface, and two endpoints. The endpoints are: endpoint 0 to form the default control pipe and endpoint 1 to form an interrupt pipe that is mandatory in HID device specification.

The requests

Morphy USB-IO accepts the following requests through the default control pipe.

The descriptors

Morphy USB-IO supports the following descriptors:

Software Interface

Communication

Morphy USB-IO is an HID device. However, it behaves somewhat differently than usual HID devices.

To communicate with Morphy USB-IO, host PC uses two types of communication units: command and response. A command is an 8 byte data sent from the host PC to the USB-IO, which is passed as a payload of a SET REPORT request. A response is an 8 byte data sent from the USB-IO to the host PC, which is passed on an Interrupt transfer.

There is no requirement to use a command and a response as a pair. That is, the host PC may send two or more commands without receiving responses, and it may receive two or more responses without sending commands.

Commands

A command always consists of 8 bytes. The first byte of a command represents a command code that specifies the type of the command. Other 7 bytes are used for parameters to the command. When the parameters are less than 7 bytes in length, remaining bytes are unused and may be set to any value (don't care.)

Morphy USB-IO doesn't allow any command that is less than 7 bytes in length.

USB-IO version 2 firmware accepts following command codes. (The name of commands are assigned by the author of this page.)

0x01: WRITE PORT 0
To write data to Port #0. The command takes a one-byte parameter x. Execution of this command causes the entire 8 bits of the value of the parameter x to be written to Port #0.
0x02: WRITE PORT 1
To write data to Port #1. The command takes a one-byte parameter x. Execution of this command causes the lower 4 bits of the value of the parameter x to be written to port #1. Upper 4 bits of x should be set to ones, although they don't affect the visible behaviour of USB-IO device. (I believe it is not a good practice to set those bits to zeros.)
0x03: READ PORT 0
To read data from Port #0 and prepare the read value for transmission to the host. The command takes no parameters. Execution of this command causes the entire 8 bits of Port #0 to be read and the read value to be stored in memory internal to the USB-IO. The command itself doesn't cause the read value to be sent to the host PC. (See explanations of Response for details.) To utilize a pin as an input, you need to write one to the corresponding bit (e.g., by WRITE PORT 0 command) before issuing this command.
0x04: READ PORT 1
To read data from Port #1 and prepare the read value for transmission to the host. The command takes no parameters. Execution of this command causes the entire 4 bits of Port #1 to be read and the read value to be stored in memory internal to the USB-IO. The command itself doesn't cause the read value to be sent to the host PC. (See explanations of Response for details.) The read bits are stored as lower 4 bits in a byte. Upper 4 bits in the bytes are unspecified. To utilize a pin as an input, you need to write one to the corresponding bit (e.g., by WRITE PORT 0 command) before issuing this command.
0x10: WRITE PORT 0 WITH STROBE ON P1.0
To write data to Port #0 with a strobe signal on bit 0 of Port #1. The command takes a one-byte parameter x. Execution of this command causes the entire 8 bits of the value of the parameter x to be written to Port #0 and a strobe signal (pulse) to be generated on bit 0 of Port #1 after that. (Details of the strobe signal will be discussed later.) The levels of the pins of Port #0 is held after the end of strobe signal. So the behaviour on Port #0 is exactly same as in the case of WRITE PORT 0. This command is only available on Morphy USB-IO ver. 2 firmware. Ver. 1 firmware doesn't support it.
0x11: WRITE PORT 0 WITH STROBE ON P1.1
To write data to Port #0 with a strobe signal on bit 1 of Port #1. This command is same as WRITE PORT 0 WITH STROBE ON P1.0 except that the strobe signal is generated on bit 1.
0x12: WRITE PORT 0 WITH STROBE ON P1.2
To write data to Port #0 with a strobe signal on bit 2 of Port #1. This command is same as WRITE PORT 0 WITH STROBE ON P1.0 except that the strobe signal is generated on bit 2.
0x13: WRITE PORT 0 WITH STROBE ON P1.3
To write data to Port #0 with a strobe signal on bit 3 of Port #1. This command is same as WRITE PORT 0 WITH STROBE ON P1.0 except that the strobe signal is generated on bit 3.
0x14: READ PORT 0 WITH STROBE ON P1.0
To read data from Port #0 with a strobe signal on bit 0 of Port #1 and prepare the read data for transmission to the host. This command takes no parameters. Execution of this command firstly causes a strobe signal to begin appearing on the bit 0 of Port #1, bits on Port #0 to be read and stored in memory internal to USB-IO after some delay during the strobe signal is active, and then the strobe signal to terminate. (Details of the strobe signal will be discussed later.) Behaviour on Port #0 is exactly same as in the case of READ PORT 0. This command is only available on Morphy USB-IO ver. 2 firmware. Ver. 1 firmware doesn't support it.
0x15: READ PORT 0 WITH STROBE ON P1.1
To read data from Port #0 with a strobe signal on bit 1 of Port #1 and prepare the read data for transmission to the host. This command is same as READ PORT 0 WITH STROBE ON P1.0 except that the strobe signal is generated on bit 1.
0x16: READ PORT 0 WITH STROBE ON P1.2
To read data from Port #0 with a strobe signal on bit 2 of Port #1 and prepare the read data for transmission to the host. This command is same as READ PORT 0 WITH STROBE ON P1.0 except that the strobe signal is generated on bit 2.
0x17: READ PORT 0 WITH STROBE ON P1.3
To read data from Port #0 with a strobe signal on bit 3 of Port #1 and prepare the read data for transmission to the host. This command is same as READ PORT 0 WITH STROBE ON P1.0 except that the strobe signal is generated on bit 3.

The Responses

There are two patterns of responses.

After executing a READ-type command (0x03, 0x04, 0x14, 0x15, 0x16 or 0x17), a response holds the value read from the port in its first byte (lower 4 bits of the first byte if the last command was READ PORT 1, entire 8 bits otherwise,) and the remaining seven bytes are copied from the corresponding bytes of the command. After executing a WRITE-type command (0x01, 0x02, 0x10, 0x11, 0x12 or 0x13), entire eight bytes in a response holds exact copy of the command.

Note that, Morphy USB-IO doesn't explicitly provide a way to match a response with the corresponding command. This may be a problem, although I'm not exactly sure why.

About strobe signal

Morphy USB-IO firmware ver. 2 or later provides I/O with strobe commands (0x10 to 0x17.) In USB-IO, strobe signal is always active-low.

Strobe signal works roughly as follows:

  1. The pin on which strobe signal will appear is initially set to High level.
  2. The pin goes to Low level to indicate the timing of actual I/O.
  3. The pin returns to High level after the I/O operation is complete.

The following issues should be noted when using strobe:

Access via Windows

(TBD)

Access via FreeBSD

(TBD)
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