asix-sigma: Adjust clock configuration upon acquisition start

Configure the samplerate clock and channel count during acquisition
start in identical ways for 50MHz, 100MHz, and 200MHz modes.

This part was inspired by work done by jry@ yet was addressed in
different ways (no exception, do everything in every mode the same way).

Eliminate a portability issue in the previous implementation. Make sure
to send the configuration bytes in the correct order to the hardware.
Don't typecase a struct reference to a bytepointer and hope that the
internal memory representation might fit the external hardware's idea.

diff --git a/src/hardware/asix-sigma/api.c b/src/hardware/asix-sigma/api.c
index c8665aae9f106a7c6845eaae1bd988e7fa8334ce..5bcce1d9ac3ced56d068dece5803d5588d1b7745 100644 (file)
--- a/src/hardware/asix-sigma/api.c
+++ b/src/hardware/asix-sigma/api.c
@@ -291,11 +291,13 @@ static int dev_acquisition_start(const struct sr_dev_inst *sdi)
 {
        struct dev_context *devc;
        struct clockselect_50 clockselect;
-       int frac, triggerpin, ret;
+       int triggerpin, ret;
        uint8_t triggerselect;
        struct triggerinout triggerinout_conf;
        struct triggerlut lut;
        uint8_t regval;
+       uint8_t clock_bytes[sizeof(clockselect)];
+       size_t clock_idx;
 
        if (sdi->status != SR_ST_ACTIVE)
                return SR_ERR_DEV_CLOSED;
@@ -356,27 +358,31 @@ static int dev_acquisition_start(const struct sr_dev_inst *sdi)
        sigma_set_register(WRITE_TRIGGER_SELECT1, triggerselect, devc);
 
        /* Set clock select register. */
-       if (devc->cur_samplerate == SR_MHZ(200))
+       clockselect.async = 0;
+       clockselect.fraction = 1 - 1;           /* Divider 1. */
+       clockselect.disabled_channels = 0x0000; /* All channels enabled. */
+       if (devc->cur_samplerate == SR_MHZ(200)) {
                /* Enable 4 channels. */
-               sigma_set_register(WRITE_CLOCK_SELECT, 0xf0, devc);
-       else if (devc->cur_samplerate == SR_MHZ(100))
+               clockselect.disabled_channels = 0xf0ff;
+       } else if (devc->cur_samplerate == SR_MHZ(100)) {
                /* Enable 8 channels. */
-               sigma_set_register(WRITE_CLOCK_SELECT, 0x00, devc);
-       else {
+               clockselect.disabled_channels = 0x00ff;
+       } else {
                /*
-                * 50 MHz mode (or fraction thereof). Any fraction down to
-                * 50 MHz / 256 can be used, but is not supported by sigrok API.
+                * 50 MHz mode, or fraction thereof. The 50MHz reference
+                * can get divided by any integer in the range 1 to 256.
+                * Divider minus 1 gets written to the hardware.
+                * (The driver lists a discrete set of sample rates, but
+                * all of them fit the above description.)
                 */
-               frac = SR_MHZ(50) / devc->cur_samplerate - 1;
-
-               clockselect.async = 0;
-               clockselect.fraction = frac;
-               clockselect.disabled_channels = 0;
-
-               sigma_write_register(WRITE_CLOCK_SELECT,
-                                    (uint8_t *) &clockselect,
-                                    sizeof(clockselect), devc);
+               clockselect.fraction = SR_MHZ(50) / devc->cur_samplerate - 1;
        }
+       clock_idx = 0;
+       clock_bytes[clock_idx++] = clockselect.async;
+       clock_bytes[clock_idx++] = clockselect.fraction;
+       clock_bytes[clock_idx++] = clockselect.disabled_channels & 0xff;
+       clock_bytes[clock_idx++] = clockselect.disabled_channels >> 8;
+       sigma_write_register(WRITE_CLOCK_SELECT, clock_bytes, clock_idx, devc);
 
        /* Setup maximum post trigger time. */
        sigma_set_register(WRITE_POST_TRIGGER,