BX-24 code conversion

DH* · Guest

I have a BX-24 application which exhausted the limits of that platform. It looks like the ZX-24 expands the limits just enough to allow me to add a few features I had wanted but could not shoehorn into a BX-24.

I make use of the BX-24 registers. Will the following code snippet work with the ZX-24?

dkinzer · Posted: 06 January 2006, 23:18 PM Post subject:

As written, it won't compile in either BasicX or ZBasic because TOV1 is undefined as are LoByte and HiByte. If you add these, you'll get a warning that the definitions of LoByte and HiByte hide system functions by the same name. This can be avoided if you use BasicX compatibility mode (add 'Option Language BasicX' at the beginning of the module).

Note, however, that since the CPU is running twice as fast, the counter also runs twice as fast. The effect will be that the counts will be twice as high as when run on the BX-24 using the same input signal.

The other thing that I would point out is that using the code shown will not provide accurate measurement of timing from rising edge to rising edge. If you need more accuracy you can use InputCapture() and set Register.TimerSpeed1 to 2 to get divide-by-8 resolution. Then, you'll have to allocate an array twice as large since InputCapture() stores the high time and low time separately. You can add the low time and high time together to get the cycle time.

DH* · Guest

Gee, a few hundred people have been running it for a few years on a BX-24. TOV1 is a constant defined elsewhere. I did say it was a snippet.

I did it this way precisely because InputCapture required twice as much memory.

I also disagree about the accuracy. At least on the BX-24 the accuracy was as good as InputCapture. Anyway, since a 1 is 2.2mS and a 0 is 1.1mS, µS accuracy is not of great importance.

My question, which you did not answer, was more about whether the register definitions will work.

dkinzer · Posted: 07 January 2006, 0:58 AM Post subject:

DH* · Guest

I also use the BasicX code below to make sure all the bytes have been sent before reversing a half-duplex RS485 line.

Sub FlushCom3()

Do While StatusQueue(OutCom_3)
Loop
Do While ((RAMpeek(21) And &H40) = &H40)
Loop

End Sub

Is there a way to do this in ZBasic?

mikep · Joined: 24 Sep 2005 Posts: 765 Location: Austin, TX

What does peeking at address 21 with RAMPeek(21) do? This looks like R21 which means you are making use of some undocumented function in BasicX. What am I missing here?

Is it sufficient for you to check that the queue is empty? If not then perhaps you might be able to check the USART status registers on the ATmega32.

DH* · Guest

It's not sufficient in BasicX to check the queue. Frank Manning supplied the code (and some for COM1) either in their forums or in their application notes.

Checking the USART registers won't help with a software UART.

mikep · Joined: 24 Sep 2005 Posts: 765 Location: Austin, TX

It sounds like you are making use of some undocumented feature of BasicX that Frank Manning told you about.

I'm sure Don knows the answer to this but I would assume that if the queue for a software UART is empty then all the bytes have been sent. My guess is that the byte is not taken off the queue until after it is sent on the COM channel.

dkinzer · Posted: 08 January 2006, 3:30 AM Post subject:

That won't work. ZBasic does not implement the undocumented features nor the internal structures of BasicX, i.e. it is not a BasicX clone. In the ZBasic Reference Manual in the section on compatibility it states, in part:

dkinzer · Posted: 08 January 2006, 6:35 AM Post subject:

This should accomplish the same objective and will work for any comm channel.

dkinzer · Posted: 08 January 2006, 6:39 AM Post subject:

DH* · Guest

Since this specific case is for half duplex RS485, can I save some RAM by using one queue for tx & rx?

DH* · Guest

Since this specific case is for half duplex RS485, can I save some RAM by using one queue for tx & rx?

dkinzer · Posted: 09 January 2006, 21:34 PM Post subject:

It will not work to specify the same queue for transmission and reception contemporaneously. The transmitter section will send any byte that it finds in the transmit queue. It can't distinguish between one added by user code and one added by the receiver section.

The only way to safely use the same queue for input and output is to open the port as transmit-only (specify the Rx queue as 0) send the data, close the port and re-open it as receive-only (specify the Tx queue as 0) and receive the data. Depending on the timing in your application, this may not be useful.

DH* · Guest

What about using one pin for both tx & rx? Will this be a problem?

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