USB-I/O Interface Adapter GPIO-24. Programmer's Reference Manual.
Chapter 5. Digital Outputs
The GPIO_SET_OUT_VAL command sets output values for all
pins of particular I/O port (Byte 2: PORT).
If you want to change values on certain pins use a mask (Byte 3: MASK). It is well known that a byte consists of 8 bits (which can be 0 or 1). This characteristic is used to create a mask. The mask value allows to modify certain pins, leaving rest of the pins unchanged. Note, that only the pins with mask bit set to 1 will be affected. The pins with mask bit set to 0 will leave unchanged.
I/O pins can be switched to output mode with the help of GPIO_SET_CFG command.
GPIO_SET_OUT_VAL command can be used prior to GPIO_SET_CFG to preset output values before
switching the pin to output mode. If I/O pin is already in output
mode, the output value is applied immediately.
GPIO_SET_OUT_VAL Command
| Byte 0 | GPIO_SET_OUT_VAL | Command ID (0x03). |
| Byte 1 | ECHO | Echo to associate a command with the response. |
| Byte 2 | PORT | Command execution status. |
| Byte 3 | MASK | Data mask to use while modifying I/O pin
output values. |
| Byte 4 | VAL | Bits of this byte are output values to be set on the corresponding pins. |
| Bytes 5..7 | Reserved | Reserved (must be 0). |
Command is an 8-byte array of the following format:
- Byte 0: GPIO_SET_OUT_VAL (0x03)
This byte contains command ID (command type). It should be set to 0x03.
- Byte 1: ECHO
This byte is used to associate a response received from GPIO-24 adapter with specific command. Response will contain exactly the same value in its echo byte.
- Byte 2: PORT
GPIO PORT:
0 – GPIO PORT A
1 – GPIO PORT B
2 – GPIO PORT C
- Byte 3: MASK
Data mask to use when modifying
I/Opin output values. The mask value allows to modify certain pins, leaving rest of the pins unchanged. Note, that only the pins with mask bit set to 1 will be affected. The pins with mask bit set to 0 will leave unchanged.- Byte 4: VAL
Bits of this byte are output values to be set on the corresponding pins.
- Bytes 5..7: Reserved
These bytes are reserved for future usage and must be set to 0.
For convenience GPIO_SET_OUT_VAL_CMD structure is declared in reports.h file.
GPIO-24 adapter sends GPIO_SET_OUT_VAL response after command execution.
GPIO_SET_OUT_VAL Response
| Byte 0 | GPIO_SET_OUT_VAL | Response ID (0x20). |
| Byte 1 | ECHO | Echo to associate a command with the response. |
| Byte 2 | ST | Command execution status. |
| Bytes 3..7 | Reserved | Reserved |
Response is an 8-byte array of the following format:
- Byte 0: GPIO_SET_OUT_VAL (0x03)
Response ID (response type). This byte will contain 0x03.
- Byte 1: ECHO
Echo byte copied from the corresponding command. It is used to associate the response with the specific command.
- Byte 2: ST
Status of the command execution:
GPIO_ST_SUCCESS (0x00) – The
I/Opins output values were successfully configured.GPIO_ST_INVALID_PORT (0x03) – Invalid port number has been specified.
- Bytes 3..7: Reserved
These bytes are reserved for future usage.
For convenience GPIO_SET_OUT_VAL_RSP structure is declared in reports.h file.
