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# Configure AP to EC Communication
This document provides details on how to configure the AP to EC communication
channel used on your board. The [AP to EC Communication] document provides
details a system level of the operation of this feature.
## Config options
Configure the AP to EC communication channel, picking exactly one of the
following options.
- `CONFIG_HOSTCMD_SHI` - [SPI Host Interface](../ec_terms.md#shi) (SHI)
- `CONFIG_HOSTCMD_HECI` - HECI interface
- `CONFIG_HOSTCMD_LPC` - [LPC](../ec_terms.md#lpc) bus
- `CONFIG_HOSTCMD_ESPI` - [eSPI](../ec_terms.md#espi) bus
In [config.h], search for options that start with the same name as your selected
communication interface. Override defaults as needed.
## Feature Parameters
None needed in this section.
## GPIOs and Alternate Pins
The EC code requires the following signals between the AP and the EC to be
defined by each board variant.
- `GPIO_ENTERING_RW` - Output from the EC, active high signal indicates when
the EC code transitions from RO to RW code.
```c
GPIO(EC_ENTERING_RW, PIN(E, 3), GPIO_OUT_LOW)
```
- `GPIO_SYS_RESET_L` - Output from the EC, active low signal used to put the
AP into reset.
```c
GPIO(SYS_RST_ODL, PIN(C, 5), GPIO_ODR_HIGH)
```
Create `ALTERNATE()` entries for all EC signals used for AP communication. This
step can be skipped for any pins that default to communication channel
functionality.
See the [GPIO](./gpio.md) documentation for additional details on the GPIO
macros.
## Data structures
None needed in this section.
## Tasks
The `HOSTCMD` task is responsible for processing commands sent by the AP and is
always required. The typical priority is higher than the `CHIPSET` task, but
lower than the `CONSOLE` task.
```c
TASK_ALWAYS(HOSTCMD, host_command_task, NULL, LARGER_TASK_STACK_SIZE, 0) \
```
## Testing and Debugging
For Nuvoton EC chipsets, the file [./chip/npcx/registers.h] provides a
collection of `DEBUG_*` macros that can be used to enable extra console messages
related to a specific interface. For AP to EC communication, the `DEBUG_LPC` and
`DEBUG_ESPI` macros can help troubleshoot communication issues.
[./chip/npcx/registers.h]: ../../chip/npcx/registers.h
[AP to EC Communication]: ../ap-ec-comm.md
[config.h]: ../new_board_checklist.md#config_h
|
