NI USB 6525 Error -201278

[eduardo.olimpio]

I'm using the NI USB 6525 device to drive a DC motor. I've just used 2 digital outputs writing a bolean array to DAQ with 01, 10 or 00 if I want the motor to move left, right or to stop. The array written depends on a encoder reading. The encoder reading and the DAQ write are inside a while loop. The problem is that when I have a sudden transient of the encoder reading I get the error -201278 - Consecutive writes to a digital line occurred more frequently than the device can safely allow. But I'm sending 1 sample on demand and even if I put a 10 ms delay in the while loop (which gives a rate lower than safely allowed) I got the same message. Does anybody know about this?

Regards

[Lucianogob]

Hola,

Este error ocurre porque si sus líneas son configuradas a una velocidad muy grande ellas pueden ser dañadas. Este error ocurre para que no utilizes las líneas a una velocidad muy grande y para que así no las dañe.

La velocidad máxima que puedes utilizar para sus líneas digitales es de 5 operaciones por segundo (5 Hz) o 200 ms entre cada ciclo. Si utilizas más que esto puedes dañar sus líneas y por esto se dá el error.

Si tienes cualquer duda por favor me contesta.

Gracias.

Cordiales Saludos

[Lucianogob]

Resposta em português:

Olá,

Este erro ocorre porque se as suas linhas forem configuradas a uma velocidade muito alta elas podem ser danificadas. Este erro ocorre para que você não utilize as linhas a uma velocidade muito alta e para que assim não as danifique.

A velocidade máxima que você pode utilizar para as linhas digitais desta placa é de 5 operações por 5 segundo (5 Hz) ou 200 ms entre cada ciclo. Se você utilizar mais do que isso poderá danificar as suas linhas e receberá este erro.

Se você tiver qualquer outra dúvida por favor entre em contato.

Obrigado.

Atenciosamente,

[zazaza]

I get the same error but only in the latest DAQmx 8.9.5 (from the CD which is sent with the DIO).

I do not get the error on the DAQmx 8.6.0. (the green led flashes on the NI 6525 but i do not get this error).

For me it seems a limitation introduced by NI in the DAQmx driver in order to protect their hardware as the limitation should be only ~2ms (introduced by the relay open + close time)

Maybe someone from NI could explain this limitation of the DIO module.

extracted from the datasheet:

Switching rate (90% duty cycle) ............5 operations per second    (?)
Relay open time ......................................60 μs typ
Relay close time......................................1.2 ms typ

[MJ]

I am experiencing the same problem.  The issue persisted even after I added a 5 sec delay between two consecutive digital write calls.  Please help, thanks.

[Lucianogob]

The USB-6525 can damage its DIO lines if they are toggled too fast.  The error message was implemented in DAQmx version 8.9 to prevent users from damaging the lines.  Tasks that toggle the DIO lines, built on the DAQmx driver prior to version 8.9, will not see this error message but still may be causing damage.  As such, users should upgrade to at least DAQmx 8.9 to ensure that the frequency of the DIO cycling will not damage the module.

The toggle rate of the USB-6525 can be found on page 14 from the detailed specifications link below.  It is listed at 5 operations per second (5 Hz), or a 200 ms period between each cycle. 

Please let me know if you need any further information.

Thanks.

Best Regards

[MJ]

Thanks for the quick response.  I double checked my code and added 250mS delay after each digital write call.  The problem is resolved.

[Lucianogob]

I'm glad to help!!!

[AConaci]

I recently ran into this issue of being limited to 5 Hz output max. Perhaps this limitation is necessary for greater current / voltage situations wherein the device may become damaged by heat; not sure. I have 12 vdc / 50 mA and wanted to go at a rate of around 100 Hz. I found downgrading to NI-DAQmx version 8.8 permitted a rate greater than 5 Hz...in fact I was running at 100 Hz without issue. Further, I removed the plastic shell on the USB-6525 to see if any components were getting hot and determined that was not the case at least in 20 second bursts. This is obviously a work around and should be done with caution at your own risk!...afterall NI put the limitation in for a reason. If you happen to know the reason for the limitation please do a post.

[yerinar]

Dear all,

thanks for this discussion. Our department is using the USB6525 for a HMI interface and we use NI-DAQmx version 9.4. We use the digital output lines in a self-written DLL-software which sets and resets the lines. A self-made function helps us to keep the requirement "Switching rate (90% duty cycle):  5 operations per second". So if 2 switching operations on 1 digital output line following in sequence there will be a pause of 210 ms between.

The time between settings had been measured and controlled via output on console.

Now if we use the DLL in real environment we get the error -201278 anyway. But the problem is we cannot reproduce the error. The error appears sporadically after several hours of working DLL. The current solution is to do a loop over the Set/Reset operation in case of failure. Then the software processes the operation and after some hours the error appears again. Increasing the pause time between is not acceptable and doesn't help also in tests. 

Can you tell me why the error still appears although we meet the requirement?

The operations we use:

1) DAQmxCreateTask

2) DAQmxCreateDOChan: with DAQmx_Val_ChanForAllLines

3) DAQmxStartTask

4) DAQmxWriteDigitalLines: with autostart = true and timeout = 1.0

Is NI working on a solution for that point in the specification? I don't understand the described requirement in combination with the solid-state relays in use.

Kind regards