small tool for controlling digital RF step atteunators attached via linux GPIOs
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/* Tool to control ZX76-31R5-SP-S+ digital attenuators on LTHW Main unit */
/* (C) 2016 by sysmocom s.f.m.c. GmbH <info@sysmocom.de>
* All Rights Reserved
*
* Author: Philipp Maier
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as published by
* the Free Software Foundation; either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <stdio.h>
#include <stdint.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <libgen.h>
#include <osmocom/core/talloc.h>
#include <osmocom/core/utils.h>
#include "gpio.h"
/* GPIO pin assignment */
#define GPIO_LE_1 13
#define GPIO_LE_2 7
#define GPIO_LE_3 5
#define GPIO_LE_4 11
#define GPIO_DATA 15
#define GPIO_CLK 17
/* Internal GPIO alias */
#define LE_1 0
#define LE_2 1
#define LE_3 2
#define LE_4 3
#define DATA 4
#define CLK 5
/* ZX76-31R5-SP-S+ properties */
#define DB_MAX 31.5
/* Generate a clock or latch enable pulse */
static inline void gpio_pulse(struct gpio_descr *gd, unsigned int gpio)
{
gpio_set(gd, gpio, 1);
gpio_set(gd, gpio, 0);
}
/* Write control word to Attenuator */
void att_write(struct gpio_descr *gd, uint8_t cw, unsigned int le)
{
int i;
unsigned int bit;
/* Write control word (val) to Attenuator */
for (i = 5; i >= 0; i--) {
bit = ((cw >> i) & 1);
gpio_set(gd, DATA, bit);
gpio_pulse(gd, CLK);
}
/* Generate latch enable pulse */
gpio_pulse(gd, le);
}
/* Initalize attenuators */
struct gpio_descr *att_init(void)
{
unsigned int gpios[6];
struct gpio_descr *gd;
/* GPIO pin mapping */
gpios[LE_1] = GPIO_LE_1;
gpios[LE_2] = GPIO_LE_2;
gpios[LE_3] = GPIO_LE_3;
gpios[LE_4] = GPIO_LE_4;
gpios[DATA] = GPIO_DATA;
gpios[CLK] = GPIO_CLK;
/* Open GPIO */
gd = gpio_open(NULL, gpios, 6);
if (!gd) {
printf("Error: Unable to open GPIO\n");
exit(1);
}
/* Initalize GPIOs to low level */
gpio_set(gd, LE_1, 0);
gpio_set(gd, LE_2, 0);
gpio_set(gd, LE_3, 0);
gpio_set(gd, LE_4, 0);
gpio_set(gd, DATA, 0);
gpio_set(gd, CLK, 0);
return gd;
}
/* Set attenuator value */
void att_set(struct gpio_descr *gd, double val, unsigned int le)
{
uint8_t cw;
if (val > DB_MAX || val < 0) {
printf("Error: Invalid attenuation value!\n");
return;
}
printf("Setting attenuator #%d to value %.1lf...\n", le + 1, val);
cw = (uint8_t) (val * 2);
att_write(gd, cw, le);
}
/* Print online help */
void print_help(char *progname)
{
printf("Usage: %s -i ID -a ATT\n", progname);
printf("Attenuation (ATT) in 0.5db steps, range 0-31.5\n");
printf("\n");
exit(0);
}
int main(int argc, char *argv[])
{
struct gpio_descr *gd;
int option;
double getopt_att = -1;
int getopt_id = -1;
/* Parse options */
while ((option = getopt(argc, argv, "hi:a:")) != -1) {
switch (option) {
case 'h':
print_help(basename(argv[0]));
break;
case 'a':
getopt_att = atof(optarg);
break;
case 'i':
getopt_id = atoi(optarg) - 1;
break;
}
}
/* Check options */
if (getopt_att < 0) {
printf("Error: No attenuation value specified!\n");
exit(1);
}
if (getopt_id < 0) {
printf("Error: No attenuator id specified!\n");
exit(1);
}
if (getopt_id > 3) {
printf("Error: Invalid attenuator id specified!\n");
exit(1);
}
/* Set attenuation */
gd = att_init();
att_set(gd, getopt_att, getopt_id);
gpio_close(gd);
return 0;
}