TS-7100-Z ADC

The TS-7100-Z supports five 12-bit ADC inputs using the i.MX6UL CPU's integrated ADC. Four of these inputs can sample 0-12VDC or 0-20mA. The fifth can sample 0-50VDC.

The pin assignments and names for accessing each ADC input are:

CN32 pin	Pin label	Schematic name	CPU signal	6UL GPIO	gpio-line-name	ADC	IIO name	Range
27	4	AN_0	6UL_AN_0	GPIO1_IO04	AN_CH0	ADC1_IN4	voltage4	0-50 V
25	5	AN_1_STC	6UL_AN_1	GPIO1_IO05	AN_CH1	ADC1_IN5	voltage5	0-12 V
23	8	AN_2_STC	6UL_AN_2	GPIO1_IO08	AN_CH2	ADC1_IN8	voltage8	0-12 V
21	9	AN_3_STC	6UL_AN_3	GPIO1_IO09	AN_CH3	ADC1_IN9	voltage9	0-12 V
19	0	AN_4_STC	6UL_AN_4	GPIO1_IO00	AN_CH4	ADC1_IN0	voltage0	0-12 V

To switch an ADC to 0-20mA current-loop receiver mode, the appropriate enable must be set high. These are EN_CL_1 through EN_CL_4, and are controlled by GPIO commands as shown below.

ADC Table

Pin label	Schematic Name	IIO Name	0-12 V Select	0-20 mA Loop Select	read-back
5	AN_1_STC	voltage5	gpioset $(gpiofind EN_CL_1)=0	gpioset $(gpiofind EN_CL_1)=1	gpioget $(gpiofind EN_ADC1_12V)
8	AN_2_STC	voltage8	gpioset $(gpiofind EN_CL_2)=0	gpioset $(gpiofind EN_CL_2)=1	gpioget $(gpiofind EN_ADC2_12V)
9	AN_3_STC	voltage9	gpioset $(gpiofind EN_CL_3)=0	gpioset $(gpiofind EN_CL_3)=1	gpioget $(gpiofind EN_ADC3_12V)
0	AN_4_STC	voltage0	gpioset $(gpiofind EN_CL_4)=0	gpioset $(gpiofind EN_CL_4)=1	gpioget $(gpiofind EN_ADC4_12V)

Note:

Only the four 0-12 V ADC inputs — corresponding with the pins labeled 5, 8, 9, and 0 in the above tables — can be used as current-loop receivers.

IIO Access to ADCs

The preferred way to access these ADCs is through the Linux Industrial I/O Subsystem (IIO), which provides sample rates up to 6ksps across all inputs. The simplest API it offers for slow speed acquisition is via sysfs (/sys):

cat /sys/bus/iio/devices/iio:device0/in_voltage{4,5,8,9,0}_raw

The fastest API is in C which will get about 6ksps:

/* Build with gcc adc-test.c -o adc-test -liio 
 * Gets ~6ksps
 * At the time of writing this does not support the buffer interface */

#include <stdint.h>
#include <stdio.h>
#include <string.h>
#include <assert.h>
#include <stdio.h>
#include <errno.h>
#include <iio.h>

uint32_t scale_mv(uint32_t raw, uint32_t max_mv)
{
	/* scale a 0-4095 raw reading to 0-max_mv mV */
	uint32_t val = raw * max_mv / 4095;

	return val;
}

int main(int argc, char **argv)
{
	static struct iio_context *ctx;
	static struct iio_device *dev;
	static struct iio_channel *chn[5];
	int i, ret;
	long long sample;

	ctx = iio_create_default_context();
	assert(ctx);
	dev = iio_context_find_device(ctx, "2198000.adc");
	assert(dev);

	chn[0] = iio_device_find_channel(dev, "voltage4", false);
	chn[1] = iio_device_find_channel(dev, "voltage5", false);
	chn[2] = iio_device_find_channel(dev, "voltage8", false);
	chn[3] = iio_device_find_channel(dev, "voltage9", false);
	chn[4] = iio_device_find_channel(dev, "voltage0", false);

	for (i = 0; i < 5; i++) {
		ret = iio_channel_attr_read_longlong(chn[i], "raw", &sample);
		assert(!ret);

		printf("AN_CH%d_mv=%d\n", i, scale_mv((uint32_t)sample, (i == 0) ? 50000 : 13325));
	}

	return 0;
}

The Python bindings currently achieve about 2ksps with similar code.

#!/usr/bin/env python

import iio

ctx = iio.Context('local:')
dev = ctx.find_device('2198000.adc')

scan_channels = ["voltage4", "voltage5", "voltage8", "voltage9", "voltage0"]

for chan_name in scan_channels:
	chan_n = int(chan_name[len("voltage"):])
	chn = dev.find_channel(chan_name)
	raw = int(chn.attrs['raw'].value)

	# Scale 0-4095 raw value to 0-12 V or 0-50 V for ADC 4.
	voltage_range = 50. if chan_n == 4 else 12.
	scaled = raw * voltage_range / 4095
	print('ADC1_IN{}={:.3f}'.format(chan_n, scaled))