X-Git-Url: https://sigrok.org/gitweb/?a=blobdiff_plain;f=src%2Fhardware%2Fasix-sigma%2Fprotocol.c;h=80e60706085fd110bf75befda024ae5b46180118;hb=b65649f6b9dca28829e4f242ae79c75db767fdfa;hp=9819e892508632e73bb2c8a7326b083acefed5c6;hpb=80e717b3cfac82d63c98614fe6179fb0e4fdaf8d;p=libsigrok.git

diff --git a/src/hardware/asix-sigma/protocol.c b/src/hardware/asix-sigma/protocol.c
index 9819e892..80e60706 100644
--- a/src/hardware/asix-sigma/protocol.c
+++ b/src/hardware/asix-sigma/protocol.c
@@ -27,22 +27,22 @@
 #include "protocol.h"
 
 /*
- * The ASIX Sigma supports arbitrary integer frequency divider in
- * the 50MHz mode. The divider is in range 1...256 , allowing for
- * very precise sampling rate selection. This driver supports only
- * a subset of the sampling rates.
+ * The ASIX SIGMA hardware supports fixed 200MHz and 100MHz sample rates
+ * (by means of separate firmware images). As well as 50MHz divided by
+ * an integer divider in the 1..256 range (by the "typical" firmware).
+ * Which translates to a strict lower boundary of around 195kHz.
+ *
+ * This driver "suggests" a subset of the available rates by listing a
+ * few discrete values, while setter routines accept any user specified
+ * rate that is supported by the hardware.
  */
 SR_PRIV const uint64_t samplerates[] = {
-	SR_KHZ(200),	/* div=250 */
-	SR_KHZ(250),	/* div=200 */
-	SR_KHZ(500),	/* div=100 */
-	SR_MHZ(1),	/* div=50  */
-	SR_MHZ(5),	/* div=10  */
-	SR_MHZ(10),	/* div=5   */
-	SR_MHZ(25),	/* div=2   */
-	SR_MHZ(50),	/* div=1   */
-	SR_MHZ(100),	/* Special FW needed */
-	SR_MHZ(200),	/* Special FW needed */
+	/* 50MHz and integer divider. 1/2/5 steps (where possible). */
+	SR_KHZ(200), SR_KHZ(500),
+	SR_MHZ(1), SR_MHZ(2), SR_MHZ(5),
+	SR_MHZ(10), SR_MHZ(25), SR_MHZ(50),
+	/* 100MHz/200MHz, fixed rates in special firmware. */
+	SR_MHZ(100), SR_MHZ(200),
 };
 
 SR_PRIV const size_t samplerates_count = ARRAY_SIZE(samplerates);
@@ -313,10 +313,16 @@ SR_PRIV int sigma_write_trigger_lut(struct triggerlut *lut, struct dev_context *
 /*
  * Initiate slave serial mode for configuration download. Which is done
  * by pulsing PROG_B and sensing INIT_B. Make sure CCLK is idle before
- * initiating the configuration download. Run a "suicide sequence" first
- * to terminate the regular FPGA operation before reconfiguration.
+ * initiating the configuration download.
+ *
+ * Run a "suicide sequence" first to terminate the regular FPGA operation
+ * before reconfiguration. The FTDI cable is single channel, and shares
+ * pins which are used for data communication in FIFO mode with pins that
+ * are used for FPGA configuration in bitbang mode. Hardware defaults for
+ * unconfigured hardware, and runtime conditions after FPGA configuration
+ * need to cooperate such that re-configuration of the FPGA can start.
  */
-static int sigma_fpga_init_bitbang(struct dev_context *devc)
+static int sigma_fpga_init_bitbang_once(struct dev_context *devc)
 {
 	uint8_t suicide[] = {
 		BB_PIN_D7 | BB_PIN_D2,
@@ -348,9 +354,11 @@ static int sigma_fpga_init_bitbang(struct dev_context *devc)
 	sigma_write(suicide, sizeof(suicide), devc);
 	sigma_write(suicide, sizeof(suicide), devc);
 	sigma_write(suicide, sizeof(suicide), devc);
+	g_usleep(10 * 1000);
 
 	/* Section 2. part 2), pulse PROG. */
 	sigma_write(init_array, sizeof(init_array), devc);
+	g_usleep(10 * 1000);
 	ftdi_usb_purge_buffers(&devc->ftdic);
 
 	/* Wait until the FPGA asserts INIT_B. */
@@ -367,6 +375,27 @@ static int sigma_fpga_init_bitbang(struct dev_context *devc)
 	return SR_ERR_TIMEOUT;
 }
 
+/*
+ * This is belt and braces. Re-run the bitbang initiation sequence a few
+ * times should first attempts fail. Failure is rare but can happen (was
+ * observed during driver development).
+ */
+static int sigma_fpga_init_bitbang(struct dev_context *devc)
+{
+	size_t retries;
+	int ret;
+
+	retries = 10;
+	while (retries--) {
+		ret = sigma_fpga_init_bitbang_once(devc);
+		if (ret == SR_OK)
+			return ret;
+		if (ret != SR_ERR_TIMEOUT)
+			return ret;
+	}
+	return ret;
+}
+
 /*
  * Configure the FPGA for logic-analyzer mode.
  */