chpp/platform/aoc/chpp_uart_link_manager.cc

/*
 * Copyright (C) 2020 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "chpp/platform/chpp_uart_link_manager.h"

#include "chpp/macros.h"
#include "chpp/platform/log.h"

namespace chpp {

UartLinkManager::UartLinkManager(UART *uart, uint8_t wakeOutPinNumber)
    : mUart(uart), mWakeOutGpio(wakeOutPinNumber) {
  mWakeOutGpio.SetDirection(GPIO::DIRECTION::OUTPUT);
  mWakeOutGpio.Clear();
}

bool UartLinkManager::prepareTxPacket(uint8_t *buf, size_t len) {
  bool success = !hasTxPacket();
  if (!success) {
    CHPP_LOGE("Cannot prepare packet while one pending");
  } else {
    mCurrentBuffer = buf;
    mCurrentBufferLen = len;
  }
  return success;
}

void UartLinkManager::startTransaction() {
  mWakeOutGpio.Set(true /* set */);

  // TODO: Wait for wake_in GPIO high

  if (hasTxPacket()) {
    int bytesTransmitted = mUart->Tx(mCurrentBuffer, mCurrentBufferLen);

    // Deassert wake_out as soon as data is transmitted, per specifications.
    mWakeOutGpio.Clear();

    if (static_cast<size_t>(bytesTransmitted) != mCurrentBufferLen) {
      CHPP_LOGE("Failed to transmit data");
    }
    // TODO: Inform CHPP transport layer of the transmission result
    clearTxPacket();
  } else {
    // TODO: Wait for pulse width requirement per specifications.
    mWakeOutGpio.Clear();
  }

  // TODO: Wait for wake_in GPIO low
}

bool UartLinkManager::hasTxPacket() const {
  return mCurrentBuffer != nullptr && mUart != nullptr;
}

void UartLinkManager::clearTxPacket() {
  mCurrentBuffer = nullptr;
}

}  // namespace chpp