Move gc_ds182x_readout to a subdir, add README.

de821c1d · Tristan Gingold · 2c67ec27 · de821c1d · 2c67ec27 · de821c1d
Commit de821c1d authored Jun 19, 2019 by Tristan Gingold
4 changed files
--- a/modules/common/Manifest.py
+++ b/modules/common/Manifest.py
@@ -31,7 +31,7 @@ files = [
    "gc_dec_8b10b.vhd",
    "gc_dyn_extend_pulse.vhd",
    "gc_ds182x_interface.vhd",
-    "gc_ds182x_readout.vhd",
+    "gc_ds182x_readout/gc_ds182x_readout.vhd",
    "gc_sfp_i2c_adapter.vhd",
    "gc_async_counter_diff.vhd",
    "gc_sync_word_wr.vhd",

--- a/modules/common/gc_ds182x_readout.vhd
+++ b/modules/common/gc_ds182x_readout.vhd
--- a/modules/common/gc_ds182x_readout/README.md
+++ b/modules/common/gc_ds182x_readout/README.md
+## gc_ds182x_readout
+
+The gc_ds182x_readout core provides a direct interface to the high-precision 1-wire digital termometer DS1820 chip.
+
+The temperature is read every second.  The read process is either triggered by the `pps_p_i` input or started automatically from the clock if the generic `g_USE_INTERNAL_PPS` is set to True.  Note that the DS18B20 chip needs up to 750ms to read the temperature.
+
+It is important to correctly set the frequency as the 1-wire protocol is time based.
+
+When using the DS18B20 (like on the SPEC), the temperature is in 1/16 degrees.
\ No newline at end of file
--- a/modules/common/gc_ds182x_readout/gc_ds182x_readout.vhd
+++ b/modules/common/gc_ds182x_readout/gc_ds182x_readout.vhd
@@ -59,8 +59,8 @@ architecture arch of gc_ds182x_readout is
  constant SLOT_CNT_START         : unsigned(15 downto 0) := to_unsigned(0*g_CLOCK_FREQ_KHZ/40000, 16);
  constant SLOT_CNT_START_PLUSONE : unsigned(15 downto 0) := SLOT_CNT_START + 1;
  constant SLOT_CNT_SET           : unsigned(15 downto 0) := to_unsigned(60*g_CLOCK_FREQ_KHZ/40000, 16);
-  constant SLOT_CNT_RD            : unsigned(15 downto 0) := to_unsigned(600*g_CLOCK_FREQ_KHZ/40000, 16);
-  constant SLOT_CNT_STOP          : unsigned(15 downto 0) := to_unsigned(3600*g_CLOCK_FREQ_KHZ/40000, 16);
+  constant SLOT_CNT_RD            : unsigned(15 downto 0) := to_unsigned(600*g_CLOCK_FREQ_KHZ/40000, 16); -- 15us
+  constant SLOT_CNT_STOP          : unsigned(15 downto 0) := to_unsigned(3600*g_CLOCK_FREQ_KHZ/40000, 16); -- 90us
  constant SLOT_CNT_PRESTOP       : unsigned(15 downto 0) := to_unsigned((3600-60)*g_CLOCK_FREQ_KHZ/40000, 16);

  constant READ_ID_HEADER     : std_logic_vector(7 downto 0) := X"33";
@@ -225,6 +225,7 @@ begin
    case state_op is

      when READ_ID_OP =>
+        --  Read the ROM (unique ID).  This is done once after reset.
        header  <= READ_ID_HEADER;
        bit_top <= ID_LGTH;
        if state_cm = IDLE_CM then
@@ -232,14 +233,17 @@ begin
        end if;

      when CONV_OP1 =>
+        --  Start conversion.
        header  <= CONVERT_HEADER;
        cm_only <= '1';

      when SKIP_ROM_OP1 =>
+        -- Skip rom to directly reads the registers.
        header  <= SKIPHEADER;
        cm_only <= '1';

      when READ_TEMP_OP =>
+        --  Read registers
        header  <= READ_TEMPER_HEADER;
        bit_top <= TEMPER_LGTH;
        if state_cm = IDLE_CM then
@@ -247,10 +251,12 @@ begin
        end if;

      when SKIP_ROM_OP2 =>
+        -- Skip rom to directly reads the registers.
        header  <= SKIPHEADER;
        cm_only <= '1';

      when CONV_OP2 =>
+        --  Start conversion.
        header  <= CONVERT_HEADER;
        cm_only <= '1';

@@ -364,11 +370,13 @@ begin
    crc_ok           <= '0';
    case state_cm is
      when RST_CM =>
+        --  Reset pulse.
        rst_bit_cnt      <= '1';
        nx_serial_id_out <= '0';
        nx_serial_id_oe  <= '1';
        init             <= start_p;
      when PREP_WR_CM =>
+        --  Presence pulse.
        rst_bit_cnt      <= start_p;
        nx_serial_id_oe  <= '0';
        nx_serial_id_out <= '0';