1 files changed, 109 insertions, 20 deletions

diff --git a/src/OfdmGenerator.cpp b/src/OfdmGenerator.cpp
index d6698c2..16eb8d9 100644
--- a/src/OfdmGenerator.cpp
+++ b/src/OfdmGenerator.cpp
@@ -582,6 +582,114 @@ int OfdmGeneratorFixed::process(Buffer* const dataIn, Buffer* dataOut)
 }
 
 #ifdef HAVE_DEXTER
+#include <gpiod.h>
+
+#define CHIP_PATH "/dev/gpiochip0"
+#define LINE_FWD_INV 0
+#define LINE_CONFIG_TDATA_VALID 31
+
+// GPIO mapping on write:
+// bit 31 config_tdata_tvalid
+// bit 30 resets the latches in the xfft_wrapper
+// bits 15..0 are 1:1 xfft `config_tdata`
+// `GPIO[0] = FWD_INV` according to Vivado
+
+static struct gpiod_line_request *
+request_output_lines(const char *chip_path, const unsigned int *offsets,
+             enum gpiod_line_value *values, unsigned int num_lines,
+             const char *consumer)
+{
+    struct gpiod_request_config *rconfig = NULL;
+    struct gpiod_line_request *request = NULL;
+    struct gpiod_line_settings *settings;
+    struct gpiod_line_config *lconfig;
+    struct gpiod_chip *chip;
+    unsigned int i;
+    int ret;
+
+    chip = gpiod_chip_open(chip_path);
+    if (!chip)
+        return NULL;
+
+    settings = gpiod_line_settings_new();
+    if (!settings)
+        goto close_chip;
+
+    gpiod_line_settings_set_direction(settings,
+                      GPIOD_LINE_DIRECTION_OUTPUT);
+
+    lconfig = gpiod_line_config_new();
+    if (!lconfig)
+        goto free_settings;
+
+    for (i = 0; i < num_lines; i++) {
+        ret = gpiod_line_config_add_line_settings(lconfig, &offsets[i],
+                              1, settings);
+        if (ret)
+            goto free_line_config;
+    }
+    gpiod_line_config_set_output_values(lconfig, values, num_lines);
+
+    if (consumer) {
+        rconfig = gpiod_request_config_new();
+        if (!rconfig)
+            goto free_line_config;
+
+        gpiod_request_config_set_consumer(rconfig, consumer);
+    }
+
+    request = gpiod_chip_request_lines(chip, rconfig, lconfig);
+
+    gpiod_request_config_free(rconfig);
+
+free_line_config:
+    gpiod_line_config_free(lconfig);
+
+free_settings:
+    gpiod_line_settings_free(settings);
+
+close_chip:
+    gpiod_chip_close(chip);
+
+    return request;
+}
+
+// The GPIO is connected to the config AXI bus of the xfft block.
+// 15..0 is the config data; 31 is tvalid
+void set_fft_accelerator_config(bool inverse)
+{
+    constexpr size_t NUM_LINES = 2;
+    unsigned int line_offsets[NUM_LINES];
+    enum gpiod_line_value values[NUM_LINES];
+
+    line_offsets[0] = LINE_CONFIG_TDATA_VALID;
+    values[0] = GPIOD_LINE_VALUE_INACTIVE;
+
+    line_offsets[1] = LINE_FWD_INV;
+    values[1] = inverse ? GPIOD_LINE_VALUE_INACTIVE : GPIOD_LINE_VALUE_ACTIVE;
+
+    struct gpiod_line_request *request;
+
+    request = request_output_lines(CHIP_PATH, line_offsets, values, NUM_LINES, "fft-config");
+    if (!request) {
+        fprintf(stderr, "failed to request line: %s\n", strerror(errno));
+        throw std::runtime_error("Request GPIO lines error");
+    }
+
+    usleep(100000);
+
+    values[0] = GPIOD_LINE_VALUE_ACTIVE;
+    gpiod_line_request_set_values(request, values);
+
+    usleep(100000);
+
+    values[0] = GPIOD_LINE_VALUE_INACTIVE;
+    gpiod_line_request_set_values(request, values);
+
+    gpiod_line_request_release(request);
+}
+
+
 OfdmGeneratorDEXTER::OfdmGeneratorDEXTER(size_t nbSymbols,
                              size_t nbCarriers,
                              size_t spacing,
@@ -599,26 +707,7 @@ OfdmGeneratorDEXTER::OfdmGeneratorDEXTER(size_t nbSymbols,
 
     etiLog.level(info) << "Using DEXTER FFT Accelerator for fixed-point transform";
 
-    // I tried to get this to work in code using libgpiod, but life is too short to waste time on that.
-    // It works through gpioset, so we just call it
-    // The GPIO is connected to the config AXI bus of the xfft block.
-    // 15..0 is the config data; 31 is tvalid
-    if (inverse) {
-        if (system("gpioset gpiochip0 0=0 31=0") != 0)
-            throw std::runtime_error("Failed to call gpioset #1");
-        if (system("gpioset gpiochip0 0=0 31=1") != 0)
-            throw std::runtime_error("Failed to call gpioset #2");
-        if (system("gpioset gpiochip0 0=0 31=0") != 0)
-            throw std::runtime_error("Failed to call gpioset #3");
-    }
-    else {
-        if (system("gpioset gpiochip0 0=1 31=0") != 0)
-            throw std::runtime_error("Failed to call gpioset #1");
-        if (system("gpioset gpiochip0 0=1 31=1") != 0)
-            throw std::runtime_error("Failed to call gpioset #2");
-        if (system("gpioset gpiochip0 0=1 31=0") != 0)
-            throw std::runtime_error("Failed to call gpioset #3");
-    }
+    set_fft_accelerator_config(inverse);
 
     if (nbCarriers > spacing) {
         throw std::runtime_error("OfdmGenerator nbCarriers > spacing!");