Problem starting after power outage

[nlrb]

I'm running the OTG with firmware 4.0b1. It is a version without a MAX232 and with a USR-TCP232-T to convert the TTL signals to Ethernet. The USR-TCP232-T is powered by a separate 5V power supply.

Problem I have is the following. When restoring power after a complete power out (i.e. both OTG and USR-TCP232-T are without power) the OTG won't start up. It will blink LEDs A-C once every second. To start up the OTG I have to take the power off (and keep it on the USR-TCP232-T) and put the power back on. Then the LEDs will flash once before the OTG starts.

Don't recall this happing with FW3.4, but this was a long time back so I don't know if it is related.

Any suggestion how to cure this?

[hvxl]

Problem I have is the following. When restoring power after a complete power out (i.e. both OTG and USR-TCP232-T are without power) the OTG won't start up. It will blink LEDs A-C once every second.

LEDs A-C? On a reset all 4 LEDs (A-D) blink very briefly. During normal operation LED B should flash twice per second. You are saying that you see the brief reset blink once every second? The only reason I can imagine for that is that the TTL to ethernet device is sending break conditions on the serial line (pulling it low). I have no idea why it would do that. I don't have such a device myself, so I can't verify or debug the behavior you report.

[nlrb]

LEDs A-C? On a reset all 4 LEDs (A-D) blink very briefly.

It seems that one LED doesn't work at all anymore. I'll need to look into that.

The only reason I can imagine for that is that the TTL to ethernet device is sending break conditions on the serial line (pulling it low). I have no idea why it would do that.

I can connect to the USR-TCP232-T at that point, but nothing is visible in otmonitor. When I only pull the power on the USR-TCP232-T, the LEDs on the OTG will flash very quickly.

[hvxl]

When I only pull the power on the USR-TCP232-T, the LEDs on the OTG will flash very quickly.

I can imagine that the USR-TCP232-T device will pull the serial line low when it is powered down. However, in theory, that should not cause the LEDs to flash. The gateway is supposed to wait for the line to go high before resetting. I may have to do some experiments to determine if that works as intended.

I didn't consider this scenario when I wrote the firmware. I now realize it would be better to not let such a situation prevent all opentherm communications.

[nlrb]

I've installed the latest FW (4.0b2), which I believe should fix this ('A continuous BREAK condition on the serial interface should not stop the gateway from handling opentherm messages.'). However, after a complete power failure the LEDs still keep flashing once a second. How long should they do this max.?

[hvxl]

It should not be doing that at all. The LEDs are supposed to flash only once. Unfortunately I don't have a USR-TCP232-T to test with, so my attempt at a fix was purely theoretical. But apparently the device is doing something other than simply pulling the line low.

[trie]

I've installed the latest FW (4.0b2), which I believe should fix this ('A continuous BREAK condition on the serial interface should not stop the gateway from handling opentherm messages.'). However, after a complete power failure the LEDs still keep flashing once a second. How long should they do this max.?

I have exact the same problem. The gateway has to be powered off and on again before stuff works again. Leds keep flashing indeed, as if it's constantly rebooting. When disconnecting the USB even more christmassy-light-spectacles appear

I'm using a PL2303 TTL to USB converter to connect to a RPi.

[nlrb]

The situation can be reproduced by an OTG setup without MAX232. If you leave the TTL signals unconnected, then you get this behavior. I can reproduce it without the USR-TCP232-T.

[hvxl]

That's how I tested the firmware. Works for me.

[nlrb]

Really strange. Any idea what can cause the difference in behavior?

[hvxl]

After studying the PIC16F88 data sheet again, I actually do have an idea.

Background: The gateway interprets a BREAK condition on the serial line ("space" (i.e. low) level for more than a full character) as a request to go to self-programming mode. This condition is detected via a framing error on the serial interface. The code then waits for the RB2 input port (which is the same pin as the serial RX port) to go high before jumping to the self-programming code. To really enter self-programming mode, a special character must be received within 1 second. If that doesn't happen, the gateway resets, flashes the LEDs and (re)starts normal operation.

Unfortunately the RB2 input port and the serial RX port have different ideas about what's low and high. The RB2 port uses a TTL input buffer, where anything below 0.8V is low and anything above 2V is high. The area between 0.8V and 2V is undefined and can turn out as either level. The serial RX port however uses a Schmitt trigger buffer. Once the input has been below 1V, the level remains low until the voltage goes above 4V. It then remains high until the voltage drops below 1V again.

The effect you see where the LEDs are flashing once per second means that the serial interface detects a framing error, then RB2 is found to be high, the self-programming code waits 1 second, the gateway resets and the whole thing starts over again.

This is possible due to the different interpretations of the logical levels: When the gateway is powered up, the port starts out at 0V and both RX and RB2 consider the logical level low. However, if the port is floating (or apparently when it is connected to an unpowered USB interface) the voltage may rise high enough for RB2 to consider it high, but not high enough to cross the upper threshold of the RX Schmitt trigger. In other words, probably somewhere between 2 and 4 Volts.

I could modify the firmware to briefly make RB2 an output and pull it high. That should flip the RX pin to high, and as long as it doesn't go below 1V again it will not cause a framing error and the gateway would possibly continue to run. I don't really like doing that though, because RB2 is normally connected to the output of another device. Connecting two outputs together may damage either of the two, although the risk of that is probably quite low if RB2 is only configured as an output for a few microseconds.

A better solution in my opinion is to do it in hardware. If you add a resistor between the RX pin and Vcc (or GND, but Vcc is preferred if that works), that should hopefully give a consistent idea of the logical level to both RX and RB2. Experiment with the value you need. I would start at around 10K. I could also try doing this in firmware using the internal pull-up resistors, but those are called "weak pull-ups" for a reason. They will probably not be strong enough to pull a powered down USB device output above 4V. But if you find that you only need a 33K resistor to Vcc to make the problem go away, that is something we could try.

[hvxl]

Hi Schelte,

Thanks very much for looking into this. I've been experimenting with 10k & 33k resistors connected to Vcc or GND. Can't say that I notice any difference.

• No external power supply connected: LEDs flashing frantically (almost continuous).
• Connected to external power supply (but powered off): LEDs flashing once a second. This can start off with 1 flash, then 3 seconds nothing and then all LEDs flashing once a second.

However, I then found that the gateway is acting strange even if it starts up correctly. With no thermostat or boiler connected is keeps issuing status reads about once every seconds (but it sometimes also stops for some seconds). This occurs even in monitor mode

(Original posting lost due to database crash)

When I suggested to start with 10k, I didn't mean to also stop there again. If 10k doesn't work, try lower values.

What does "flashing frantically" look like? Can you make a short video of that?

The gateway is not "acting strange" when it sends messages in case no thermostat is disconnected. It is supposed to do that. And without the boiler connected it doesn't get a response, so it keeps repeating the same message. When (it thinks) the thermostat is connected again, the gateway stops generating messages. If the detection mechanism sometimes concludes that the thermostat is connected when it's not, your 24V may be a bit low or the value of R5/R6 may be off.

[nlrb]

Post of 18-2-2014; re-posting due to database crash.

Hi Schelte,

Thanks very much for looking into this. I've been experimenting with 10k & 33k resistors connected to Vcc or GND. Can't say that I notice any difference.

• No external power supply connected: LEDs flashing frantically (almost continuous).
• Connected to external power supply (but powered off): LEDs flashing once a second. This can start off with 1 flash, then 3 seconds nothing and then all LEDs flashing once a second.

However, I then found that the gateway is acting strange even if it starts up correctly. With no thermostat or boiler connected is keeps issuing status reads about once every seconds (but it sometimes also stops for some seconds). This occurs even in monitor mode See log below (contains some power cycles).

Code: Select all

11:08:51.993373  R00000000  Read-Data   Status: 00000000 00000000
11:08:57.966416  R00000000  Read-Data   Status: 00000000 00000000
11:09:02.536269  Thermostat connected
11:09:09.657993  ROpenTherm R00000000
11:09:13.689506  b2
11:09:13.755126  Thermostat disconnected
11:09:13.833932  R00000000  Read-Data   Status: 00000000 00000000
11:09:13.861510  R00000000  Read-Data   Status: 00000000 00000000
11:09:13.886048  R00000000  Read-Data   Status: 00000000 00000000
11:09:13.913252  R00000000  Read-Data   Status: 00000000 00000000
11:09:15.638011  R00000000  Read-Data   Status: 00000000 00000000
11:09:16.626706  R00000000  Read-Data   Status: 00000000 00000000
11:09:17.631729  R00000000  Read-Data   Status: 00000000 00000000
11:09:18.617726  R00000000  Read-Data   Status: 00000000 00000000
11:09:19.613418  R00000000  Read-Data   Status: 00000000 00000000
11:09:20.608740  R00000000  Read-Data   Status: 00000000 00000000
11:09:21.604373  R00000000  Read-Data   Status: 00000000 00000000
11:09:22.600233  R00000000  Read-Data   Status: 00000000 00000000
11:09:23.597775  R00000000  Read-Data   Status: 00000000 00000000
11:09:24.591085  R00000000  Read-Data   Status: 00000000 00000000
11:09:25.586536  R00000000  Read-Data   Status: 00000000 00000000
11:09:26.582106  R00000000  Read-Data   Status: 00000000 00000000
11:09:27.576502  R00000000  Read-Data   Status: 00000000 00000000
11:09:28.572907  R00000000  Read-Data   Status: 00000000 00000000
11:09:29.568438  R00000000  Read-Data   Status: 00000000 00000000
11:09:30.563892  R00000000  Read-Data   Status: 00000000 00000000
11:09:31.558599  R00000000  Read-Data   Status: 00000000 00000000
11:09:32.555275  R00000000  Read-Data   Status: 00000000 00000000
11:09:33.550771  R00000000  Read-Data   Status: 00000000 00000000
11:09:34.547962  R00000000  Read-Data   Status: 00000000 00000000
11:09:35.541583  R00000000  Read-Data   Status: 00000000 00000000
11:09:36.536788  R00000000  Read-Data   Status: 00000000 00000000
11:09:37.532241  R00000000  Read-Data   Status: 00000000 00000000
11:09:38.527717  R00000000  Read-Data   Status: 00000000 00000000
11:09:39.524297  R00000000  Read-Data   Status: 00000000 00000000
11:09:40.519108  R00000000  Read-Data   Status: 00000000 00000000
11:09:41.514008  R00000000  Read-Data   Status: 00000000 00000000
11:09:42.509601  R00000000  Read-Data   Status: 00000000 00000000
11:09:43.506169  R00000000  Read-Data   Status: 00000000 00000000
11:09:44.500586  R00000000  Read-Data   Status: 00000000 00000000
11:09:45.496040  R00000000  Read-Data   Status: 00000000 00000000
11:09:46.491414  R00000000  Read-Data   Status: 00000000 00000000
11:09:47.486898  R00000000  Read-Data   Status: 00000000 00000000
11:09:48.482401  R00000000  Read-Data   Status: 00000000 00000000
11:09:49.317327  Thermostat connected
11:19:40.633703  R00000000  Read-Data   Status: 00000000 00000000
11:19:41.629132  R00000000  Read-Data   Status: 00000000 00000000
11:19:42.624549  R00000000  Read-Data   Status: 00000000 00000000
11:19:43.620064  R00000000  Read-Data   Status: 00000000 00000000
11:19:44.615420  R00000000  Read-Data   Status: 00000000 00000000
11:19:45.303864  Command: PR=M
11:19:45.594033  PR: M=G
11:19:45.612672  R00000000  Read-Data   Status: 00000000 00000000
11:19:46.606233  R00000000  Read-Data   Status: 00000000 00000000
11:19:47.601688  R00000000  Read-Data   Status: 00000000 00000000
11:19:48.597075  R00000000  Read-Data   Status: 00000000 00000000
11:19:48.865800  Command: GW=0
11:19:48.891346  GW: 0
11:19:49.592464  R00000000  Read-Data   Status: 00000000 00000000
11:19:50.587921  R00000000  Read-Data   Status: 00000000 00000000
11:19:51.583379  R00000000  Read-Data   Status: 00000000 00000000
11:19:52.578802  R00000000  Read-Data   Status: 00000000 00000000
11:19:53.574254  R00000000  Read-Data   Status: 00000000 00000000
11:19:54.569679  R00000000  Read-Data   Status: 00000000 00000000
11:19:55.565107  R00000000  Read-Data   Status: 00000000 00000000
11:19:56.560372  R00000000  Read-Data   Status: 00000000 00000000
11:19:57.555821  R00000000  Read-Data   Status: 00000000 00000000
11:19:58.551261  R00000000  Read-Data   Status: 00000000 00000000
11:19:59.546564  R00000000  Read-Data   Status: 00000000 00000000
11:20:00.541960  R00000000  Read-Data   Status: 00000000 00000000
11:20:01.098281  Command: GW=1
11:20:01.123924  GW: 1
11:20:01.537387  R00000000  Read-Data   Status: 00000000 00000000
11:20:02.532812  R00000000  Read-Data   Status: 00000000 00000000
11:20:03.528272  R00000000  Read-Data   Status: 00000000 00000000
11:20:04.523672  R00000000  Read-Data   Status: 00000000 00000000
11:20:05.518915  R00000000  Read-Data   Status: 00000000 00000000
11:20:06.514358  R00000000  Read-Data   Status: 00000000 00000000
11:20:07.509793  R00000000  Read-Data   Status: 00000000 00000000
11:20:08.505264  R00000000  Read-Data   Status: 00000000 00000000
11:20:09.500685  R00000000  Read-Data   Status: 00000000 00000000
11:20:10.495934  R00000000  Read-Data   Status: 00000000 00000000
11:20:11.491422  R00000000  Read-Data   Status: 00000000 00000000
11:20:12.486791  R00000000  Read-Data   Status: 00000000 00000000
11:20:13.482249  R00000000  Read-Data   Status: 00000000 00000000
11:20:14.477684  R00000000  Read-Data   Status: 00000000 00000000
11:20:15.473081  R00000000  Read-Data   Status: 00000000 00000000
11:20:16.468382  R00000000  Read-Data   Status: 00000000 00000000
11:20:17.463801  R00000000  Read-Data   Status: 00000000 00000000
11:20:18.459205  R00000000  Read-Data   Status: 00000000 00000000
11:20:19.454637  R00000000  Read-Data   Status: 00000000 00000000
11:20:20.449989  R00000000  Read-Data   Status: 00000000 00000000
11:20:21.445339  R00000000  Read-Data   Status: 00000000 00000000
11:20:22.440715  R00000000  Read-Data   Status: 00000000 00000000
11:20:23.436048  R00000000  Read-Data   Status: 00000000 00000000
11:20:24.431398  R00000000  Read-Data   Status: 00000000 00000000
11:20:25.426815  R00000000  Read-Data   Status: 00000000 00000000
11:20:26.443390  Thermostat connected
11:26:19.615200  pÿOpÿOpÿOpÿOpÿOpÿOpÿOpÿOpÿOpenTherm Gateway 4.0b2
11:26:19.646228  Thermostat disconnected
11:26:23.761287  R00000000  Read-Data   Status: 00000000 00000000
11:26:24.757072  R00000000  Read-Data   Status: 00000000 00000000
11:26:25.752741  R00000000  Read-Data   Status: 00000000 00000000
11:26:26.748436  R00000000  Read-Data   Status: 00000000 00000000
11:26:27.744267  R00000000  Read-Data   Status: 00000000 00000000
11:26:28.740012  R00000000  Read-Data   Status: 00000000 00000000
11:26:29.735696  R00000000  Read-Data   Status: 00000000 00000000
11:26:30.732591  R00000000  Read-Data   Status: 00000000 00000000
11:26:31.726996  R00000000  Read-Data   Status: 00000000 00000000
11:26:32.722688  R00000000  Read-Data   Status: 00000000 00000000
11:26:37.701205  R00000000  Read-Data   Status: 00000000 00000000
11:26:37.720238  R00000000  Read-Data   Status: 00000000 00000000
11:26:38.696840  R00000000  Read-Data   Status: 00000000 00000000
11:26:39.692606  R00000000  Read-Data   Status: 00000000 00000000
11:26:40.688308  R00000000  Read-Data   Status: 00000000 00000000
11:26:41.684044  R00000000  Read-Data   Status: 00000000 00000000
11:26:42.679668  R00000000  Read-Data   Status: 00000000 00000000
11:26:43.675418  R00000000  Read-Data   Status: 00000000 00000000
11:26:44.671154  R00000000  Read-Data   Status: 00000000 00000000
11:26:45.666830  R00000000  Read-Data   Status: 00000000 00000000
11:26:46.662467  R00000000  Read-Data   Status: 00000000 00000000
11:26:47.658162  R00000000  Read-Data   Status: 00000000 00000000
11:26:48.653906  R00000000  Read-Data   Status: 00000000 00000000
11:26:49.407493  Command: GW=1
11:26:49.426257  GW: 1
11:26:49.649569  R00000000  Read-Data   Status: 00000000 00000000
11:26:50.645251  R00000000  Read-Data   Status: 00000000 00000000
11:26:51.640948  R00000000  Read-Data   Status: 00000000 00000000
11:26:52.636704  R00000000  Read-Data   Status: 00000000 00000000
11:26:53.632398  R00000000  Read-Data   Status: 00000000 00000000
11:26:54.628150  R00000000  Read-Data   Status: 00000000 00000000
11:26:54.663683  Command: PR=A
11:26:54.706923  PR: A=OpenTherm Gateway 4.0b2
11:26:55.623726  R00000000  Read-Data   Status: 00000000 00000000
11:26:56.619493  R00000000  Read-Data   Status: 00000000 00000000
11:26:57.615148  R00000000  Read-Data   Status: 00000000 00000000
11:26:58.610908  R00000000  Read-Data   Status: 00000000 00000000
11:26:59.606560  R00000000  Read-Data   Status: 00000000 00000000
11:27:00.602257  R00000000  Read-Data   Status: 00000000 00000000
11:27:01.597901  R00000000  Read-Data   Status: 00000000 00000000
11:27:02.593495  R00000000  Read-Data   Status: 00000000 00000000
11:27:03.589135  R00000000  Read-Data   Status: 00000000 00000000
11:27:04.584767  R00000000  Read-Data   Status: 00000000 00000000
11:27:05.580418  R00000000  Read-Data   Status: 00000000 00000000
11:27:06.575973  R00000000  Read-Data   Status: 00000000 00000000
11:27:07.571721  R00000000  Read-Data   Status: 00000000 00000000
11:27:08.567250  R00000000  Read-Data   Status: 00000000 00000000
11:27:09.562848  R00000000  Read-Data   Status: 00000000 00000000
11:27:10.558508  R00000000  Read-Data   Status: 00000000 00000000
11:27:52.875703  OpenTherm Gateway 4.0b3
11:27:52.906784  Thermostat disconnected
11:27:57.021091  R00000000  Read-Data   Status: 00000000 00000000
11:27:58.016648  R00000000  Read-Data   Status: 00000000 00000000
11:27:59.012155  R00000000  Read-Data   Status: 00000000 00000000
11:28:00.007663  R00000000  Read-Data   Status: 00000000 00000000
11:28:01.003167  R00000000  Read-Data   Status: 00000000 00000000
11:28:07.971390  R00000000  Read-Data   Status: 00000000 00000000
11:28:07.991532  R00000000  Read-Data   Status: 00000000 00000000
11:28:08.966873  R00000000  Read-Data   Status: 00000000 00000000
11:28:08.985756  R00000000  Read-Data   Status: 00000000 00000000
11:28:09.962343  R00000000  Read-Data   Status: 00000000 00000000
11:28:10.957806  R00000000  Read-Data   Status: 00000000 00000000
11:28:11.953323  R00000000  Read-Data   Status: 00000000 00000000
11:28:12.948812  R00000000  Read-Data   Status: 00000000 00000000
11:28:13.944327  R00000000  Read-Data   Status: 00000000 00000000
11:28:14.939844  R00000000  Read-Data   Status: 00000000 00000000
11:28:15.935212  R00000000  Read-Data   Status: 00000000 00000000
11:28:16.930700  R00000000  Read-Data   Status: 00000000 00000000
11:28:17.926209  R00000000  Read-Data   Status: 00000000 00000000
11:28:18.921674  R00000000  Read-Data   Status: 00000000 00000000
11:28:19.917036  R00000000  Read-Data   Status: 00000000 00000000
11:28:20.912502  R00000000  Read-Data   Status: 00000000 00000000
11:28:21.907945  R00000000  Read-Data   Status: 00000000 00000000
11:28:22.903458  R00000000  Read-Data   Status: 00000000 00000000
11:28:23.898994  R00000000  Read-Data   Status: 00000000 00000000
11:28:24.894475  R00000000  Read-Data   Status: 00000000 00000000
11:28:25.890024  R00000000  Read-Data   Status: 00000000 00000000
11:28:26.885425  R00000000  Read-Data   Status: 00000000 00000000
11:28:27.880857  R00000000  Read-Data   Status: 00000000 00000000
11:28:28.442734  Command: PR=A
11:28:28.485959  PR: A=OpenTherm Gateway 4.0b3
11:28:28.876323  R00000000  Read-Data   Status: 00000000 00000000
11:28:29.871829  R00000000  Read-Data   Status: 00000000 00000000
11:28:30.586758  Command: GW=1
11:28:30.612875  GW: 1
11:28:30.867295  R00000000  Read-Data   Status: 00000000 00000000
11:28:31.862802  R00000000  Read-Data   Status: 00000000 00000000
11:28:32.858215  R00000000  Read-Data   Status: 00000000 00000000
11:28:33.853714  R00000000  Read-Data   Status: 00000000 00000000
11:28:34.849204  R00000000  Read-Data   Status: 00000000 00000000
11:28:35.844552  R00000000  Read-Data   Status: 00000000 00000000
11:28:36.049713  Thermostat connected
11:29:24.566518  R00000000  Read-Data   Status: 00000000 00000000
11:29:25.562052  R00000000  Read-Data   Status: 00000000 00000000
11:29:26.557606  R00000000  Read-Data   Status: 00000000 00000000
11:29:27.553114  R00000000  Read-Data   Status: 00000000 00000000
11:29:28.548675  R00000000  Read-Data   Status: 00000000 00000000
11:29:29.544259  R00000000  Read-Data   Status: 00000000 00000000
11:29:30.539856  R00000000  Read-Data   Status: 00000000 00000000
11:29:31.535523  R00000000  Read-Data   Status: 00000000 00000000
11:29:32.530912  R00000000  Read-Data   Status: 00000000 00000000
11:29:33.526504  R00000000  Read-Data   Status: 00000000 00000000
11:29:34.522153  R00000000  Read-Data   Status: 00000000 00000000
11:29:35.517643  R00000000  Read-Data   Status: 00000000 00000000
11:29:38.504363  R00000000  Read-Data   Status: 00000000 00000000
11:29:38.522918  R00000000  Read-Data   Status: 00000000 00000000
11:29:39.499941  R00000000  Read-Data   Status: 00000000 00000000
11:29:42.486575  R00000000  Read-Data   Status: 00000000 00000000
11:29:42.505431  R00000000  Read-Data   Status: 00000000 00000000
11:29:43.482104  R00000000  Read-Data   Status: 00000000 00000000
11:29:44.477664  R00000000  Read-Data   Status: 00000000 00000000
11:29:45.473187  R00000000  Read-Data   Status: 00000000 00000000
11:29:46.468589  R00000000  Read-Data   Status: 00000000 00000000
11:29:47.463070  R00000000  Read-Data   Status: 00000000 00000000
11:29:48.459671  R00000000  Read-Data   Status: 00000000 00000000
11:29:49.455213  R00000000  Read-Data   Status: 00000000 00000000
11:29:50.450746  R00000000  Read-Data   Status: 00000000 00000000
11:29:51.348670  Thermostat connected

I've flashed new FW without a problem, so the PIC looks to be OK I guess.

Any clue?

[nlrb]

It looks to be a grounding issue. If I just hold my finger to the GND then the OTG will start up. I've made a video of it. Let me see if I can post it later.

[nlrb]

I've uploaded the video here. In the video it looks like the LEDs are on constantly once the power is switched on. However, the human eye can see that the LEDs go off briefly numerous of times per second.