usrp-e100: add ability to set/get default master clock rate from EEPROM

Mboard eeprom map class can parse the setting (4 byte float).
The clock control will try to set the eeprom rate if present,
otherwise or under failure condition, it sets the default.

Updated docs, example, and provided helpful verbose.
I would prefer that users burn the desired rate to the eeprom (and they may too).

2 files changed, 22 insertions, 1 deletions

diff --git a/host/lib/usrp/usrp_e100/clock_ctrl.cpp b/host/lib/usrp/usrp_e100/clock_ctrl.cpp
index 1ac2b804c..851ce29b0 100644
--- a/host/lib/usrp/usrp_e100/clock_ctrl.cpp
+++ b/host/lib/usrp/usrp_e100/clock_ctrl.cpp
@@ -184,7 +184,24 @@ public:
 
         this->use_internal_ref();
 
-        this->set_fpga_clock_rate(DEFAULT_OUTPUT_RATE); //initialize to something
+        //initialize the FPGA clock to something
+        bool fpga_clock_initialized = false;
+        try{
+            if (_iface->mb_eeprom.has_key("master_clock_rate")){
+                std::cout << "Read FPGA clock rate from EEPROM setting." << std::endl;
+                const double master_clock_rate = boost::lexical_cast<double>(_iface->mb_eeprom["master_clock_rate"]);
+                std::cout << boost::format("Initializing FPGA clock to %fMHz...") % (master_clock_rate/1e6) << std::endl;
+                this->set_fpga_clock_rate(master_clock_rate);
+                fpga_clock_initialized = true;
+            }
+        }
+        catch(const std::exception &e){
+            std::cerr << "Error setting FPGA clock rate from EEPROM: " << e.what() << std::endl;
+        }
+        if (not fpga_clock_initialized){ //was not set... use the default rate
+            std::cout << boost::format("Initializing FPGA clock to %fMHz...") % (DEFAULT_OUTPUT_RATE/1e6) << std::endl;
+            this->set_fpga_clock_rate(DEFAULT_OUTPUT_RATE);
+        }
 
         this->enable_test_clock(ENABLE_THE_TEST_OUT);
         this->enable_rx_dboard_clock(false);
diff --git a/host/lib/usrp/usrp_e100/mboard_impl.cpp b/host/lib/usrp/usrp_e100/mboard_impl.cpp
index 29e3c5da2..5f4a208d3 100644
--- a/host/lib/usrp/usrp_e100/mboard_impl.cpp
+++ b/host/lib/usrp/usrp_e100/mboard_impl.cpp
@@ -207,6 +207,10 @@ void usrp_e100_impl::mboard_set(const wax::obj &key, const wax::obj &val){
         return;
 
     case MBOARD_PROP_CLOCK_RATE:
+        std::cerr << "Helpful message:" << std::endl;
+        std::cerr << "    I see that you are setting the master clock rate from the API." << std::endl;
+        std::cerr << "    You may find it more convenient to burn this setting into the EEPROM." << std::endl;
+        std::cerr << "    See the application notes for USRP-E1XX for further instructions." << std::endl;
         _clock_ctrl->set_fpga_clock_rate(val.as<double>());
         return;