DSMC 读写示例

2026-02-06

本文将介绍如何通过 DSMC 总线进行通讯，通过 DSMC 的 localbus master 与 PGL22GB 实现的 localbus server 进行通讯，并验证写入数据。

DSMC 简介

DSMC（Double Data Rate Serial Memory Controller）是瑞芯微 SoC 内部的一种高速存储与本地总线控制器，用于通过 DDR 方式与外部 PSRAM 或 LocalBus 设备（如 FPGA）进行数据通信，具有高频高速的特性。

DSMC 特性

支持双倍数据速率（DDR）接口
支持最多选择 4 个芯片
支持 8 线和 16 线串行传输模式
支持可配置的写/读连续地址合并事务
支持可配置的写/读边界地址拆分事务
支持将 WRAP 传输转换为 INCR 传输
支持字节访问
支持可配置的 DQS 输入时钟延迟线

使用 DSMC 向 FPGA 写入数据

本示例使用 DSMC localbus master 向 FPGA 写入数据，FPGA 将数据存储入大小为 16KB 的 RAM 当中，DSMC localbus master 再将写入数据读出来，进行值的判断。

硬件连接

RC-PI-3506 开发板与 FPGA 扩展板需要连接。

创建工程点击展开

构建工程点击展开

固件下载点击展开

核心示例代码

adc_sample.c
static int test_dsmc_read_write(void)
{
    int i;
    int err_count = 0;

    rt_uint64_t t_start, t_end;
    rt_uint64_t write_cycles, read_cycles;

    const int WORD_NUM = 4 * 1024;          // 4K word = 16KB
    uintptr_t BASE_ADDR = 0xC0000000;

    rt_uint32_t *write_buf = rt_malloc(WORD_NUM * 4);
    rt_uint32_t *read_buf  = rt_malloc(WORD_NUM * 4);

    if (!write_buf || !read_buf)
    {
        rt_kprintf("malloc failed!\n");
        return -1;
    }

    for (i = 0; i < WORD_NUM; i++)
    {
        write_buf[i] = 0x12345678 + i;
    }

    t_start = rt_hw_global_timer_get();

    for (i = 0; i < WORD_NUM; i++)
    {
        writel(write_buf[i], BASE_ADDR + i * 4); //RK3506读写的时候，只能4字节对齐访问
    }

    t_end = rt_hw_global_timer_get();
    write_cycles = t_end - t_start;

    t_start = rt_hw_global_timer_get();

    for (i = 0; i < WORD_NUM; i++)
    {
        read_buf[i] = readl(BASE_ADDR + i * 4);
    }

    t_end = rt_hw_global_timer_get();
    read_cycles = t_end - t_start;

    for (i = 0; i < WORD_NUM; i++)
    {
        if (read_buf[i] != write_buf[i])
        {
            err_count++;
            rt_kprintf("ERR[%d]: R=0x%08X W=0x%08X\n",
                        i, read_buf[i], write_buf[i]);

            if (err_count > 10)
            {
                rt_kprintf("......\n");
                break;
            }
        }
    }

    float write_time_us = (float)write_cycles / 24.0f;
    float read_time_us  = (float)read_cycles  / 24.0f;

    float total_bytes = WORD_NUM * 4.0f;

    float write_speed = (total_bytes / (1024 * 1024)) / (write_time_us / 1e6);
    float read_speed  = (total_bytes / (1024 * 1024)) / (read_time_us  / 1e6);

    if (err_count == 0)
    {
        rt_kprintf("\n==== DSMC TEST PASS ====\n");

        rt_kprintf("Write: %lu cycles, %.2f us, %.2f MB/s\n",
                    write_cycles, write_time_us, write_speed);

        rt_kprintf("Read : %lu cycles, %.2f us, %.2f MB/s\n",
                    read_cycles, read_time_us, read_speed);
    }
    else
    {
        rt_kprintf("\n==== DSMC TEST FAIL ====\n");
        rt_kprintf("Error count: %d\n", err_count);
    }

    rt_free(write_buf);
    rt_free(read_buf);

    return 0;
}

MSH_CMD_EXPORT(test_dsmc_read_write, test dsmc read write);

运行程序

RC-PI-3506 输出：

msh />test_dsmc_read_write

==== DSMC TEST PASS ====
Write: 73640 cycles, 3068.33 us, 5.09 MB/s
Read : 240044 cycles, 10001.83 us, 1.56 MB/s
msh />test_dsmc_read_write