Port Addressing Issue

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- 2nd November 2005, 14:56
CocaColaKid

Port Addressing Issue

This code works great for reading 5 sensors however I want to decrease the amount of time it takes to run through this subroutine by not trying to read a sensor if its not being used. My problem starts with the line "if sensor = 1 then" because it thinks I'm trying to compare the value stored in sensor which is not what I want it to do. I need it to compare the port associated with the number against a specific value. Any ideas on how to resolve this issue?

Code:

read_sensors: for sensor = 0 to 4 temp_c = 0 temp_f = 0 temp_k = 0 dummy = 0 dq = 0 gosub ds_init gosub read_temp sign_c_array[sensor] = sign_c sign_f_array[sensor] = sign_f temp_c_array[sensor] = temp_c temp_f_array[sensor] = temp_f temp_k_array[sensor] = temp_k next sensor ds_init: low sensor ' Set the data pin low to initialize pauseus 500 ' Wait for more than 480us input sensor ' Make data pin port an input pauseus 100 ' Wait for more than 60us if sensor = 1 then ' Is there a DS18B20 detected debug cmd,line3,"Not Present" ' If not set flag indicating so SensorMissing = 1 return endif pauseus 400 ' Wait for end of presence pulse debug cmd,line3,"Present " ' Set flag indicating there is a SensorMissing = 0 ' sensor present return read_temp: if SensorMissing = 1 then ' If the sensor is not present load temp_c = 32767 ' these values in place of the temp_f = 62181 ' temperature indicating there is temp_k = 60082 ' a problem with the sensor sign_c = "+" sign_f = "+" return endif owout sensor,1,[$CC,$44] ' Send start temperature conversion ' command low portb.5 ' Turn on transistor between rail and ' data pin pause 750 ' Allow enough time to process Tconv high portb.5 ' Turn off transistor between rail and ' data pin owout sensor,1,[$CC,$BE] ' Send read scratch pad command owin sensor,0,[STR dq\9] ' Read all 9 bytes and store them in dq ' array raw_temp.Byte0 = dq[0] ' Isolate raw temperature from the rest raw_temp.Byte1 = dq[1] gosub get_crc ' Calculate the CRC of the data gosub convert_temp ' Convert raw data into real temps return
- 2nd November 2005, 15:03
rhino

Quote:

read_sensors:
for sensor = 0 to 4

Can you use a different variable name here? Just a quick thought.
- 2nd November 2005, 20:06
CocaColaKid

The variable name will not matter. What I need to be is be able to step through portb.0 to portb.4 which works fine just using 0 to 4. The problem is that when "sensor" is equal to 0 the if then statement thinks that sensor is 0 and not 1 even though the port is being pulled high. As such when I do it for 2,3 and 4 the same thing. It looks at the number and not the state of the port.
- 2nd November 2005, 20:54
rhino

I see... don't think my code analogy will work, but what you are after is reading the state of the "portB.sensor" input, where sensor is the bit #... right?
- 2nd November 2005, 21:27
CocaColaKid

Bingo! That is exactly what I want
- 3rd November 2005, 12:10
hmr

Hi Cocacolakid

Try this:

PortB.0 [sensor]

If you need more info, read section 4.11 on the manual.

Hope this help.

Hans
- 3rd November 2005, 13:11
CocaColaKid

After sleeping on this I figured out an easy way to accomplish this task. I just added a subroutine that gets the port state according to the value of "sensor". I works like a charm.

Code:

read_sensors: for sensor = 0 to 4 temp_c = 0 temp_f = 0 temp_k = 0 dummy = 0 dq = 0 gosub ds_init gosub read_temp sign_c_array[sensor] = sign_c sign_f_array[sensor] = sign_f temp_c_array[sensor] = temp_c temp_f_array[sensor] = temp_f temp_k_array[sensor] = temp_k next sensor ds_init: low sensor ' Set the data pin low to initialize pauseus 500 ' Wait for more than 480us input sensor ' Make data pin port an input pauseus 100 ' Wait for more than 60us gosub direction if SensorState = 1 then ' Is there a DS18B20 detected debug cmd,line3,"Not Present" ' If not set flag indicating so SensorMissing = 1 return endif pauseus 400 ' Wait for end of presence pulse debug cmd,line3,"Present " ' Set flag indicating there is a SensorMissing = 0 ' sensor present return direction: if sensor = 0 then SensorState = portb.0 return endif if sensor = 1 then SensorState = portb.1 return endif if sensor = 2 then SensorState = portb.2 return endif if sensor = 3 then SensorState = portb.3 return endif if sensor = 4 then SensorState = portb.4 return endif read_temp: if SensorMissing = 1 then temp_c = 32767 temp_f = 62181 temp_k = 60082 sign_c = "+" sign_f = "+" return endif owout sensor,1,[$CC,$44] ' Send start temperature conversion ' command low portb.5 ' Turn on transistor between rail and ' data pin pause 750 ' Allow enough time to process Tconv high portb.5 ' Turn off transistor between rail and ' data pin owout sensor,1,[$CC,$BE] ' Send read scratch pad command owin sensor,0,[STR dq\9] ' Read all 9 bytes and store them in dq ' array raw_temp.Byte0 = dq[0] ' Isolate raw temperature from the rest raw_temp.Byte1 = dq[1] gosub get_crc ' Calculate the CRC of the data gosub convert_temp ' Convert raw data into real temps return
- 3rd November 2005, 19:15
rhino

Glad to see you found a solution. I still think there should be a way to do it similar to what I was thinking, and Hans's idea. Any thoughts from the guru's?