How delay() or microseconds() delay in platformIO for hifive1 board (Risc-v) can be written?

danielkc26 · February 20, 2020, 12:06pm

Hi,
I just started working with hifive1 with platformIO ,here i want to use delay functions, in ms and us .How it can be achieved?

maxgerhardt · February 20, 2020, 1:22pm

Which framework are you using? What’s the content of your platformio.ini?

danielkc26 · February 20, 2020, 1:37pm

env:hifive1
platform = sifive
board = hifive1

Using freedom e sdk

maxgerhardt · February 20, 2020, 4:53pm

The examples in for the Freedom-e-sdk show that a hardware timer can be used (arm with specific wait value, then run, wait for completion interrupt, then exit function). The setup function seems to be using the RTC clock (32.768 kHz) so the timers might be using this base frequency. Code e.g. shown in

github.com

platformio/platform-sifive/blob/master/examples/freedom-e-sdk_sifive-welcome/src/sifive-welcome.c#L60


      
          
          
void timer_isr (int id, void *data) {
          
          
    // Disable Timer interrupt
              metal_interrupt_disable(tmr_intr, tmr_id);
          
          
    // Flag showing we hit timer isr
              timer_isr_flag = 1;
          }
          
          
void wait_for_timer(struct metal_led *which_led) {
          
          
    // clear global timer isr flag
              timer_isr_flag = 0;
          
          
    // Turn on desired LED
              metal_led_on(which_led);
          
          
    // Set timer
              metal_cpu_set_mtimecmp(cpu, metal_cpu_get_mtime(cpu) + RTC_FREQ);

There is also a delay millisecond function written in assembly which uses the hardware timer, this can be used from C code as well. It’s the exact same concept of arming the timer and waiting for the interrupt in a blocking way.

github.com

platformio/platform-sifive/blob/master/examples/native-blink_asm/src/delay.S

# SPDX-License-Identifier: Unlicense
# Copyright (c) 2018 Western Digital Corporation or its affiliates.

.section .text
.align 2
.globl delay

.include "memory_map.inc"

# Our delay value in milliseconds passed into a0

delay:
    addi sp, sp, -16            # Setup our stack frame
    sw ra, 12(sp)               # Save return address

    li t0, MTIME                # Load the timer register
    lw t1, 0(t0)                # Load the current value of the timer

    li t2, MTIME_FREQUENCY      # Get our clock frequency
    mul t2, t2, a0              # Multiply milliseconds with frequency

This file has been truncated. show original

For more questions on the Freedom-E SDK, it’s best to use the forum of their SDK, as PlatformIO is just the build system.

danielkc26 · February 20, 2020, 5:26pm

Yes i have also seen that, and i was using Arduino ide and sometimes freedomstudio(from Sifive) ide for my projects. Very recently I heard that platformIo has give risc-v support , so I just started to use platformIO. Actually, I just wanted to know that ,any ready made functions are available related to that delay in the form of library, so that I can use it without spending much time😀. Anyways thanks a lot for your immediate response.