Byte size problems
jcfjr
Posts: 74
This is my first project using the Propeller,and usually with enough digging I have been able to understand how things work. But I have run into something I do not understand. I am using two Propeller chips in this project, and need to pass three numbers from the first Prop (U1) to the second Prop (U2). U2 is driving a 3.5 inch touchscreen and has no room for anything except driving the display, thus the need for the second Prop for my application. I am building a meter that measures two voltages, a forward and reflected voltage,and calculates some values (SWR and power), then passes these values to U2 for display, this part works. When there is no transmission to measure, I wanted to display the time on the meter. I am using the DS1302and it works fine. I want to pass the three values(integers) hour, minute, second to U2 for display. Graphics on U2 only uses strings to print, so I convert the hour, minute, second to strings before sending(no room on U2 to do this), and then print these as three separate strings on the display.
I use the following on U1 to send the values
And the following to recieve on U2
Each string is 3 bytes according to strsize , so I set the following variable sizes in U2
byte Rbuf[3]
byte hour[3]
byte minute[3]
byte second[3]
and only moved 3 bytes with bytemove for each variable.
But the display would only show seconds on it. If I change all the above variable sizes of 3 to 8 bytes, then the minute and second will display, and only if I use a size of 12 bytes will it display all three values correctly.
I thought I was sending each value separately as three byte packets, copying it to its own location, then printing it on display as a string at a specified location. Why won't this work unless I use 12 byte lengths for the four variables, it seems to me 3 bytes should work since I am printing them as separate strings at separate locations, and not as one?? I have included complete code that shows the graphics portion.
I use the following on U1 to send the values
repeat
rtc.readTime( @hour, @minute, @second ) 'read time from DS1302
'send hour, minute, second to U2 as string
Comm.str(CD.ToStr(hour,%000_000_000_0_0_000011_01010 ))
Comm.Str(String(13))
Comm.str(CD.ToStr(minute,%000_000_000_0_0_000011_01010 ))
Comm.Str(String(13))
Comm.str(CD.ToStr(second,%000_000_000_0_0_000011_01010 ))
Comm.Str(String(13))
waitcnt( 79_000_000 + cnt )
And the following to recieve on U2
Comm.Rxstr(@Rbuf)
bytemove(@hour,@Rbuf,12)
' minute := Comm.Rxstr(@Rbuf)
Comm.Rxstr(@Rbuf)
bytemove(@minute,@Rbuf,12)
' second := Comm.Rxstr(@Rbuf)
Comm.Rxstr(@Rbuf)
bytemove(@second,@Rbuf,12)
Each string is 3 bytes according to strsize , so I set the following variable sizes in U2
byte Rbuf[3]
byte hour[3]
byte minute[3]
byte second[3]
and only moved 3 bytes with bytemove for each variable.
But the display would only show seconds on it. If I change all the above variable sizes of 3 to 8 bytes, then the minute and second will display, and only if I use a size of 12 bytes will it display all three values correctly.
I thought I was sending each value separately as three byte packets, copying it to its own location, then printing it on display as a string at a specified location. Why won't this work unless I use 12 byte lengths for the four variables, it seems to me 3 bytes should work since I am printing them as separate strings at separate locations, and not as one?? I have included complete code that shows the graphics portion.
