display C.H.I.P power and battery status https://bbs.nextthing.co/t/pwrstat-c-talk-to-axp209-over-i2c-in-c/6710?u=yoursunny

pwrstat.c

// gcc -o pwrstat pwrstat.c
// display C.H.I.P power and battery status
// AXP209-internal-temperature USB-voltage USB-current battery-voltage [+-]battery-current
// https://bbs.nextthing.co/t/pwrstat-c-talk-to-axp209-over-i2c-in-c/6710?u=yoursunny

#define _GNU_SOURCE
#include <errno.h>
#include <fcntl.h>
#include <stdbool.h>
#include <stdlib.h>
#include <stdint.h>
#include <stdio.h>
#include <unistd.h>
#include <linux/i2c-dev.h>
#include <sys/ioctl.h>

int
readReg(int fd, int reg)
{
  uint8_t regbuf[1];
	regbuf[0] = reg  & 0xFF;
	int res = write(fd, regbuf, sizeof(regbuf));
	if (res < 0) {
	  printf("cannot read register\n");
	  exit(1);
	}

  uint8_t valbuf[1];
  res = read(fd, valbuf, sizeof(valbuf));
  if (res < 0) {
	  printf("cannot read register\n");
	  exit(1);
	}

  return valbuf[0];
}

void
writeReg(int fd, int reg, uint8_t val)
{
  uint8_t cmdbuf[2];
	cmdbuf[0] = reg  & 0xFF;
	cmdbuf[1] = val;
	int res = write(fd, cmdbuf, sizeof(cmdbuf));
	if (res < 0) {
	  printf("cannot write register\n");
	  exit(1);
	}
}

int
readAdc(int fd, int regH, int regL, int lowBits)
{
  int h = readReg(fd, regH);
  int l = readReg(fd, regL);
  return (h << lowBits) + l;
}

int
main(int argc, char** argv)
{
  int fd = open("/dev/i2c-0", O_RDWR);
  if (fd < 0) {
    perror("cannot open I2C bus");
    return 1;
  }

  int ret = ioctl(fd, I2C_SLAVE_FORCE, 0x34);
  if (ret < 0) {
    printf("cannot talk to AXP209\n");
    return 1;
  }

  int adcEnable1 = readReg(fd, 0x82);
  int adcEnable2 = readReg(fd, 0x83);
  bool needWait = false;
  if ((adcEnable1 & 0xcc) != 0xcc) {
    adcEnable1 |= 0xcc;
    writeReg(fd, 0x82, adcEnable1);
    needWait = true;
  }
  if ((adcEnable2 & 0x80) != 0x80) {
    adcEnable2 |= 0x80;
    writeReg(fd, 0x83, adcEnable2);
    needWait = true;
  }
  if (needWait) {
    sleep(1);
  }

  int powerStatus = readReg(fd, 0x00);

  int temp = readAdc(fd, 0x5E, 0x5F, 4);
  printf("%0.1fC ", 0.1 * temp - 144.7);

  bool hasVbus = (powerStatus & 0x20) != 0;
  if (hasVbus) {
    int vbusVolt = readAdc(fd, 0x5A, 0x5B, 4);
    printf("%0.1fmV ", 1.7 * vbusVolt);

    int vbusCurrent = readAdc(fd, 0x5C, 0x5D, 4);
    printf("%0.1fmA ", 0.375 * vbusCurrent);
  }
  else {
    printf("_ _ ");
  }

  int powerMode = readReg(fd, 0x01);
  bool hasBatt = (powerMode & 0x20) != 0;
  if (hasBatt) {
    int battVolt = readAdc(fd, 0x78, 0x79, 4);
    printf("%0.1fmV ", 1.1 * battVolt);

    bool isDischarging = (powerStatus & 0x04) == 0;
    bool isCharging = (powerMode & 0x40) != 0;
    if (isDischarging) {
      int dischargeCurrent = readAdc(fd, 0x7C, 0x7D, 5);
      printf("-%0.1fmA ", 0.5 * dischargeCurrent);
    }
    else if (isCharging) {
      int chargeCurrent = readAdc(fd, 0x7A, 0x7B, 4);
      printf("+%0.1fmA ", 0.5 * chargeCurrent);
    }
    else {
      printf("_ ");
    }
  }
  else {
    printf("_ _ ");
  }

  printf("\n");
  return 0;
}