TMS320F2808: Integration Problem of a Sensor and TMS320F2808 in Simulink

Hi Venkatesh,

Firstly, thanks for the quick response. You are right, the description is inefficient. Sorry about that. But as far as I searched, the problem comes down to the SCI interface and its generated code. Let me explain the hierarchy in detail and maybe you will get a better insight:

We have STIM210 where it can be read through a RS485 transceiver(ADM2582E) and this transceiver needs to be enabled before reading operation. Firstly, we enable the transceiver by an active low input and then get the gyro data as an output from it. The output pin of the transceiver is connected to SCIRXDA where we collect it via SCI Receive block in Simulink. This is the main hierarchy of reading gyro.

Now, normally we can read gyro without any error if we power up the gyro before we power up STIM210. The problem occurs when we do not power up STIM210 and power up TMS320F2808. Normally, besides gyro reading, there are several other processes and algorithms in our model which needs to operate. If we can not receive any data from gyro, our code seems to get stuck in there and does not do anything further. To reoperate, we need to power-reset our entire mechanism. When I debug into the code in Code Composer Studio, there are few things that I encounter:

-scia_rcv() function simply goes in a while loop and does not leave it for a certain time until it receives data.

-When it leaves, it returns an error which activates RXERRA and in RXERRA, there is simply a line which is asm(" nop"). It does not assign the output of SCI Receive block to anything. After that, our code gets stuck in and does not work anymore.

I hope this clarifies the problem.

Hi,

I understand the problem. But since the SCI receive is a global variable, it must read zero if no data is received. Are you not reading zero from this block as the default value. If the condition is zero what action is the application taking. Perhaps that can be a clue.

There is a delay in polling which can be overcome by using the block under interrupt context. Using the block under interrupt will help in this case.

More questions:

-Why would the frequency of the PWM signal decrease besides the situation above? I mentioned this PWM situation in my original post.

-How long that delay lasts in polling?

-For how long the polling in scia_rcv() will keep the code from performing? 

Hi,

I have made some observations. It seems that our problem comes from the working principle of SCI Receive block. If no data is received, it simply waits in the while loop until data is received for a certain amount of time. By the time the code is in that while loop, our code, which is supposed to operate at 1 millisecond, operates way much slower. After that, it leaves the while loop and also returns a timeout error which is equal to 1. One last question though:

-Is it normal that the code operates way much slower when it enters that while loop in scia_rcv() function? It does operate way much slower, I have made an observation in real time.