Read HP Common slot PSUs via I2C from NodeJS

main.js

const I2C = require("i2c-bus");

function psu_calc_checksum(addr, buf)
{
    let cs = (addr << 1);

    for(let i = 0; i < buf.length - 1; i++)
        cs += buf.readUInt8(i);

    buf.writeUInt8(((0xFF - cs) + 1) & 0xFF, buf.length - 1);
}
function psu_check_checksum(buf)
{
    let cs = 0;

    for(let i = 0; i < buf.length; i++)
        cs += buf.readUInt8(i);

    if((((0xFF - cs) + 1) & 0xFF) === 0)
        return true;

    return false;
}

async function psu_write_reg(bus, addr, reg, data)
{
    let buf = Buffer.alloc(4, 0);

    buf.writeUInt8(reg, 0);
    buf.writeUInt16LE(data, 1);

    psu_calc_checksum(addr, buf);

    return bus.i2cWrite(addr, buf.length, buf);
}
async function psu_read_reg(bus, addr, reg)
{
    let buf = Buffer.alloc(2, 0);

    buf.writeUInt8(reg, 0);

    psu_calc_checksum(addr, buf);

    await bus.i2cWrite(addr, buf.length, buf);

    buf = Buffer.alloc(3, 0);
    let result = await bus.i2cRead(addr, 3, buf);

    if(!result)
        return 0;

    if(result.bytesRead < 3)
        return 0;

    if(!psu_check_checksum(result.buffer))
        return 0;

    return result.buffer.readUInt16LE(0);
}
async function psu_read_eeprom(bus, addr, mem_addr, count)
{
    let buf = Buffer.alloc(1, 0);

    buf.writeUInt8(mem_addr, 0);

    await bus.i2cWrite(addr, buf.length, buf);

    buf = Buffer.alloc(count, 0);
    let result = await bus.i2cRead(addr, count, buf);

    if(!result)
        return 0;

    if(result.bytesRead < count)
        return 0;

    return result.buffer;
}

async function main()
{
    const psu_ee_addr = 0x57;
    const psu_addr = 0x5F;

    const I2C0 = await I2C.openPromisified(0);

    let found = await I2C0.scan();

    if(found.indexOf(psu_addr) === -1)
        return console.log("PSU not found at address %d", psu_addr);

    if(found.indexOf(psu_ee_addr) === -1)
        return console.log("PSU EEPROM not found at address %d", psu_ee_addr);

    console.log("PSU found at address %d", psu_addr);
    console.log("PSU EEPROM found at address %d", psu_ee_addr);

    console.log("-----------------");

    let psu_spn = await psu_read_eeprom(I2C0, psu_ee_addr, 0x12, 10);
    let psu_date = await psu_read_eeprom(I2C0, psu_ee_addr, 0x1D, 8);
    let psu_name = await psu_read_eeprom(I2C0, psu_ee_addr, 0x32, 26);
    let psu_ct = await psu_read_eeprom(I2C0, psu_ee_addr, 0x5B, 14);

    console.log("PSU SPN: %s", psu_spn.toString("utf8"));
    console.log("PSU Date: %s", psu_date.toString("utf8"));
    console.log("PSU Name: %s", psu_name.toString("utf8"));
    console.log("PSU CT: %s", psu_ct.toString("utf8"));

    let in_v = await psu_read_reg(I2C0, psu_addr, 0x08) / 32;
    let in_a = await psu_read_reg(I2C0, psu_addr, 0x0A) / 256;
    let in_a_max = await psu_read_reg(I2C0, psu_addr, 0x34) / 256;
    let in_w = await psu_read_reg(I2C0, psu_addr, 0x0C) / 4;
    let in_w_max = await psu_read_reg(I2C0, psu_addr, 0x32) / 4;
    let in_ws = (await psu_read_reg(I2C0, psu_addr, 0x2C) + (await psu_read_reg(I2C0, psu_addr, 0x2E) << 16)) / 4;

    let out_v = await psu_read_reg(I2C0, psu_addr, 0x0E) / 256;
    let out_a = await psu_read_reg(I2C0, psu_addr, 0x10) / 64;
    let out_a_max = await psu_read_reg(I2C0, psu_addr, 0x36) / 64;
    let out_w = await psu_read_reg(I2C0, psu_addr, 0x12) / 4;

    let intake_temp = await psu_read_reg(I2C0, psu_addr, 0x1A) / 64;
    let internal_temp = await psu_read_reg(I2C0, psu_addr, 0x1C) / 64;

    let fan_rpm = await psu_read_reg(I2C0, psu_addr, 0x1E);
    let fan_target_rpm = await psu_read_reg(I2C0, psu_addr, 0x40);

    let on_time = await psu_read_reg(I2C0, psu_addr, 0x30);

    let status_flags = await psu_read_reg(I2C0, psu_addr, 0x02);

    console.log("Input Voltage: %d V", in_v);
    console.log("Input Current: %d A (max. %d A)", in_a, in_a_max);
    console.log("Input Power: %d W (max. %d W)", in_w, in_w_max);
    console.log("Input Energy: %d kWh", in_ws / 3600000);
    console.log("Output Voltage: %d V", out_v);
    console.log("Output Current: %d A (max. %d A)", out_a, out_a_max);
    console.log("Output Power: %d W", out_w);
    console.log("Intake Temperature: %d C", intake_temp);
    console.log("Internal Temperature: %d C", internal_temp);
    console.log("Fan speed: %d RPM", fan_rpm);
    console.log("Fan target speed: %d RPM", fan_target_rpm);
    console.log("On time: %d s", on_time);
    console.log("Status flags: %d", status_flags);
    console.log("PSU ON: " + ((status_flags & 0x05) === 0x05));

    psu_write_reg(I2C0, psu_addr, 0x40, 0);
}

main();