FORM command - HMP155

Use the serial line command FORM to change the format or select certain quantities for the output commands SEND and R.

FORM x

Parameter	Description
x	Formatter string

The formatter string consists of quantities and modifiers. You can only type a maximum of 73 characters after the command on the command line.

Table 1. Quantities measured by HMP155

Quantity	Abbreviation	Metric unit	Imperial unit
Relative humidity	RH	%RH	%RH
Temperature	T	°C	°F
Additional T‑probe temperature	Ta	°C	°F

Table 2. Quantities calculated from measured quantities

Quantity	Abbreviation	Metric unit	Imperial unit
Dew point / Frost point temperature (Td/f)	TDF	°C	°F
Dew point temperature (Td)	TD	°C	°F
Mixing ratio (x)	X	g/kg	gr/lb
Wet bulb temperature (Tw)	TW	°C	°F

The modifiers are shown in the following table.

Table 3. FORM command modifiers

Modifier	Description
quantity	Quantity name (for example RH, T or TDF)
x.y	Length modifier (number of digits and decimal places)
#t	Tabulator
#r	Carriage return
#n	Line feed
“"	String constant
#xxx	Special character with decimal code "xxx"
U5	Unit field and length
ADDR	Probe address with 2 characters [00 ... 99]
CS2	Modulus-256 checksum of message sent so far, hexadecimal format.
CS4	Modulus-65536 checksum of message sent so far, hexadecimal format.
ERR	Error flags for T, Ta, RH, MEM; [0000 ... 1111]; 0 = no error, 1 =error T = temperature measurement error Ta = measurement error in the additional T-probe RH = humidity measurement error MEM = memory error For a more detailed error message, use the ERRS command and see Table 1.
STAT	Probe heating status in 1 character field, for example:
	N = no heating
	h = warmed probe active
	H = purge heating active
	S = purge cooling active
	X = extra sensor heating active
SNUM	Probe serial number
TIME	Time [hh:mm:ss]

>form "Temperature=" 5.2 t #r#n
OK
>send
Temperature=   24.23
>

>form "Twet=" 6.3 tw U3 #t "T=" t U3 #r#n
OK
>send
Twet=    11.290'C       T=    24.231'C
>

>form 5.1 rh #t t #t tdf #r#n
OK
>send
   15.6    24.2    -3.1
>

FORM / command returns the default output format. The default output format depends on the device configuration. FORM command without formatter string returns the current output format of the probe.

>form /
OK
>send
 RH= 23.8 %RH T= 19.4 'C
>

Checksums are calculated as described in the following equations.

${cs}_2={\displaystyle \sum _{i=1}^n{b}_i\mathrm{mod}256}$

${cs}_4={\displaystyle \sum _{i=1}^n{b}_i\mathrm{mod}65536}$

${cs}_x={\displaystyle {b\prime }_1\oplus {b\prime }_2\oplus \mathrm{...}\oplus {b\prime }_n}$

${b\prime }_i={\displaystyle b_{i}if{b}_i\ne 36and{b}_1\ne 42}$

${b\prime }_i={\displaystyle 0if{b}_i=36or{b}_1=42}$

Table 4. Symbols in FORM checksum equations

Symbol	Description
cs2	Value of CS2 checksum in the output message.
cs4	Value of CS4 checksum in the output message.
csx	Value of CSX checksum in the output message.
bi	Value of the byte at position i (1-based) in the output message.
n	Number of bytes in the output message before the CS2, CS4, or CSX field (including earlier checksum fields, if any).
⊕	Bit-wise exclusive OR operator.
36	Byte value of ASCII $ character.
42	Byte value of ASCII * character.