Z-uno is running much slower on PC power than on charger

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risca
Posts: 10
Joined: 11 Feb 2018 05:53

Z-uno is running much slower on PC power than on charger

Post by risca » 17 Feb 2018 00:43

Hello,

I'm creating a sketch to control my projector at home. Unfortunately, my projector requires a (9:th) parity bit for UART communication (see other topic), so I decided to bitbang the protocol. Here's the code:

Code: Select all

// LED pin number
#define LED_PIN 13

#define START_CODE ((char)0xA9)
#define END_CODE   ((char)0x9A)

static byte lastValue = 0;
static byte currentValue = 0;
//static const char onCmd[] = { START_CODE, 0x17, 0x2E, 0x00, 0x00, 0x00, 0x3F, END_CODE };
//static const char offCmd[] = { START_CODE, 0x17, 0x2F, 0x00, 0x00, 0x00, 0x3F, END_CODE };
static const char onCmd[] = "UUUUUUUU";
static const char offCmd[] = "UUUUUUUU";

s_pin txPin = 15;
unsigned long timestamp = 0;

#define INTERBIT_26_US_SLEEP delayMicroseconds(41); NOPS(23)
#define SET_TX_PIN(level) digitalWrite(txPin, level); INTERBIT_26_US_SLEEP

static void txByte(char b, bool parity)
{
  noInterrupts();
  // start bit
  SET_TX_PIN(LOW);
  // 8 data bits
  SET_TX_PIN(b & (1 << 0) ? HIGH : LOW);
  SET_TX_PIN(b & (1 << 1) ? HIGH : LOW);
  SET_TX_PIN(b & (1 << 2) ? HIGH : LOW);
  SET_TX_PIN(b & (1 << 3) ? HIGH : LOW);
  SET_TX_PIN(b & (1 << 4) ? HIGH : LOW);
  SET_TX_PIN(b & (1 << 5) ? HIGH : LOW);
  SET_TX_PIN(b & (1 << 6) ? HIGH : LOW);
  SET_TX_PIN(b & (1 << 7) ? HIGH : LOW);
  // parity
  SET_TX_PIN(parity ? HIGH : LOW);
  // stop bit
  NOPS(40); // compensate a bit for the lack of comparison
  SET_TX_PIN(HIGH);
  // for perfect bit timing we should wait some more here,
  // but we don't.
  interrupts();
}

static bool CalculateParity(byte b)
{
  bool parity = false;
  while (b) {
    parity = !parity;
    b = b & (b - 1);
  }
  return b;
}

static void TurnOnProjector()
{
  Serial.print("Turning on projector... ");
  for (int i = 0; i < 8; ++i) {
    txByte(onCmd[i], CalculateParity(onCmd[i]));
  }
  digitalWrite (LED_PIN, HIGH);
  Serial.println("done.");
}

static void TurnOffProjector()
{
  Serial.print("Turning off projector... ");
  for (int i = 0; i < 8; ++i) {
    txByte(offCmd[i], CalculateParity(offCmd[i]));
  }
  digitalWrite(LED_PIN, LOW);
  Serial.println("done.");
}

// next macro sets up the Z-Uno channels
// in this example we set up 1 switch binary channel
// you can read more on http://z-uno.z-wave.me/Reference/ZUNO_SWITCH_BINARY/
ZUNO_SETUP_CHANNELS(ZUNO_SWITCH_BINARY(getter, setter));

// this function runs only once the controller sends new value
void setter (byte value) {
  currentValue = value;
}

// this function runs only once the controller asks
byte getter () {
  return currentValue;
}

void setup() {
  Serial.begin();
  pinMode(LED_PIN, OUTPUT);
  pinMode(txPin, OUTPUT);
  currentValue = lastValue = 0;
}

void loop() {
  if(millis() - timestamp > 3000) {
    Serial.print("PING - ");
    Serial.println(timestamp);
    timestamp = millis();
  }
  if (lastValue != currentValue) {
    lastValue = currentValue; 
    if (currentValue > 0) {
      TurnOnProjector();
    }
    else {
      TurnOffProjector();
    }
    delay(3000);
  }
}
The amount of delay between each bit was determined through trial and error until I got the timing right. Now, here's the problem: when I power the z-uno with my laptop, the timing is all wrong. The z-uno seems to be running at ~50 % compared to when I use a charger. Here are some measurements I did with my oscilloscope. The first picture is when the z-uno is connected to a USB power supply (5 V, 2.5 A) and the second is when it's connected to my laptop.

Image Image

I did not re-program the z-uno between these capture. I only changed the power supply.

What is wrong?

User avatar
PoltoS
Posts: 4620
Joined: 26 Jan 2011 19:36

Re: Z-uno is running much slower on PC power than on charger

Post by PoltoS » 17 Feb 2018 18:01

Do you see this slow down effect when you power Z-Uno from a 5V USB charger. I want to exclude the possible influence from the PC sending some USB datagrams

risca
Posts: 10
Joined: 11 Feb 2018 05:53

Re: Z-uno is running much slower on PC power than on charger

Post by risca » 23 Feb 2018 02:10

I've done some more experiments on this now.
Things I have powered the z-uno with that makes it run slow:
  • my laptop (USB cable, 5 V, ? A)
  • old Siemens phone charger (5 V, 700 mA) soldered to +5 V and GND.
Things I have powered the z-uno with that makes it run fast:
  • USB charger (5 V, 2.5 A)
  • powered USB hub (5 V, 1.5 A)
I'm at a loss what could be causing this

Tillsy
Posts: 29
Joined: 15 Feb 2018 03:51

Re: Z-uno is running much slower on PC power than on charger

Post by Tillsy » 23 Feb 2018 03:23

•my laptop (USB cable, 5 V, ? A)
A computer will only provide higher amperage out the USB once it has installed with a device specific driver.

•old Siemens phone charger (5 V, 700 mA) soldered to +5 V and GND.
So in both these cases you have identified low current when it runs slow, whereas in the cases it runs fast you are talking multiple amps.

risca
Posts: 10
Joined: 11 Feb 2018 05:53

Re: Z-uno is running much slower on PC power than on charger

Post by risca » 23 Feb 2018 22:33

Yes, it seems that way. The Z-uno seem to work fine in both cases, just 2 different speeds.

User avatar
PoltoS
Posts: 4620
Joined: 26 Jan 2011 19:36

Re: Z-uno is running much slower on PC power than on charger

Post by PoltoS » 27 Feb 2018 19:03

Do you see same if powered on 3V pin?

risca
Posts: 10
Joined: 11 Feb 2018 05:53

Re: Z-uno is running much slower on PC power than on charger

Post by risca » 28 Feb 2018 04:48

I don't have any 3 V power supplies, or do you mean to connect 5 V to the 3 V pin?

Tillsy
Posts: 29
Joined: 15 Feb 2018 03:51

Re: Z-uno is running much slower on PC power than on charger

Post by Tillsy » 28 Feb 2018 13:34

Oh hell don't do that! He meant feeding a 3V source to the 3V pin - the Z-UNO natively runs 3V probably why he wants to test that.

But that's not what you're needing/trying. 5V is convenient as any USB power source will run it - but in your case you're using a few USB sources that are limiting the current.

User avatar
PoltoS
Posts: 4620
Joined: 26 Jan 2011 19:36

Re: Z-uno is running much slower on PC power than on charger

Post by PoltoS » 02 Mar 2018 00:16

NB! Don't connect 5 Volts to 3V pin!!!!

Z-Uno consumes about 50 mA without sensors connected, so your 200 mA power source should be enough.... I doubt how can this happen - UART and radio should not work neither if you see such a slow down. May be it is a faulty unit? Do you have a spare one?

petergebruers
Posts: 230
Joined: 26 Jul 2015 17:29

Re: Z-uno is running much slower on PC power than on charger

Post by petergebruers » 02 Mar 2018 16:49

Long shot... Could it be some MCU pins pick up noise? That alone does not not explain what you see, the noise should also trigger something like an interrupt. Also I think all inputs default to weak pull-up, but to be on the safe side, could you set all unused pins to output mode?

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