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// Copyright 2022 The Pigweed Authors
// 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
// 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 <cinttypes>
#include "mss_gpio/mss_gpio.h"
#include "mss_uart/mss_uart.h"
#include "pw_preprocessor/concat.h"
#include "pw_status/status.h"
#include "pw_sys_io/sys_io.h"
#include "pw_sys_io_emcraft_sf2_private/config.h"
namespace {
constexpr mss_gpio_id_t kDs3LedGPIO = MSS_GPIO_1;
constexpr mss_gpio_id_t kDs4LEDGPIO = MSS_GPIO_2;
constexpr uint32_t kDs3LedMask = MSS_GPIO_1_MASK;
constexpr uint32_t kDs4LedMask = MSS_GPIO_2_MASK;
constexpr uint32_t kReadDataReady = 0x1u;
} // namespace
extern "C" void pw_sys_io_Init() {
// Configure MSS GPIOs.
// Set LEDs to initial app state
MSS_GPIO_set_outputs(MSS_GPIO_get_outputs() | kDs4LedMask);
// Initialize the UART0 controller (57600, 8N1)
// Due to a HW eratta in SF2, we need to run at 57600 for
// in-system-programming mode. If we are not upgrading FPGA or flash then we
// can use a faster BAUD.
// This whole implementation is very inefficient because it uses the synchronous
// polling UART API and only reads / writes 1 byte at a time.
namespace pw::sys_io {
Status ReadByte(std::byte* dest) {
while (true) {
if (TryReadByte(dest).ok()) {
return OkStatus();
Status TryReadByte(std::byte* dest) {
if (!(g_mss_uart0.hw_reg->LSR & kReadDataReady)) {
return Status::Unavailable();
*dest = static_cast<std::byte>(g_mss_uart0.hw_reg->RBR);
return OkStatus();
Status WriteByte(std::byte b) {
// Wait for TX buffer to be empty. When the buffer is empty, we can write
// a value to be dumped out of UART.
const uint8_t pbuff = (uint8_t)b;
MSS_UART_polled_tx(&g_mss_uart0, &pbuff, 1);
return OkStatus();
// Writes a string using pw::sys_io, and add newline characters at the end.
StatusWithSize WriteLine(const std::string_view& s) {
size_t chars_written = 0;
StatusWithSize result = WriteBytes(std::as_bytes(std::span(s)));
if (!result.ok()) {
return result;
chars_written += result.size();
// Write trailing newline.
result = WriteBytes(std::as_bytes(std::span("\r\n", 2)));
chars_written += result.size();
return StatusWithSize(OkStatus(), chars_written);
} // namespace pw::sys_io