HP E1429A manual Readings, Language Example 16-bit readings

C Language Example (16-bit readings)

/* dynamically allocate memory for readings */ rdgs = malloc(20 * sizeof(int));

/* set number of bytes placed in memory, and number of bytes read */ swap = sizeof(int);/* place 2 bytes/reading in memory */

bytes = 20 * swap;/* read 40 bytes */

IOOUTPUTS(ADDR, "READ?", 5);/* retrieve the readings */

IOENTERAB(ADDR, rdgs, &bytes, swap); /* enter the readings */

/* and remove the block header */

/* Remove line feed which trails the last data byte */ length = 1;

IOENTERS(ADDR, lf_remove, &length);

The command which removes the block header from the readings is

IOENTERAB. The parameters passed to IOENTERAB are:

ADDR - the address of the digitizer

rdgs - the array name which will store the readings

bytes - a variable specifying the maximum number of bytes to be read

swap - a variable specifying how the bytes are placed into memory (2 bytes per reading)

Converting Packed The equation for converting packed readings is:

Readings

readingvoltage = (readingpacked / 16) * reading resolution

Reading resolution is a function of the signal range. The resolutions for the digitizer signal ranges are given in Table 3-2.

Table 3-2. Reading Resolutions for Packed Data Conversions

Signal Range	Resolution	Signal Range	Resolution
-0.1023 to 0.10235	0.00005	-5.115 to 5.1175	0.0025
-0.2046 to 0.2047	0.00010	-10.230 to 10.235	0.005
-0.5115 to 0.51175	0.00025	-20.460 to 20.470	0.010
-1.0230 to 1.0235	0.0005	-51.15 to 51.175	0.025
-2.0460 to 2.0470	0.0010	-102.30 to 102.35	0.05

136 Understanding the HP E1429 Digitizer Chapter 3