diff --git a/pid/buildjson.cpp b/pid/buildjson.cpp
new file mode 100644
index 0000000..d89da92
--- /dev/null
+++ b/pid/buildjson.cpp
@@ -0,0 +1,106 @@
+/**
+ * Copyright 2019 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "pid/buildjson.hpp"
+
+#include "conf.hpp"
+
+#include <map>
+#include <nlohmann/json.hpp>
+#include <tuple>
+
+using json = nlohmann::json;
+
+void from_json(const json& j, ControllerInfo& c)
+{
+    j.at("type").get_to(c.type);
+    j.at("inputs").get_to(c.inputs);
+    j.at("setpoint").get_to(c.setpoint);
+
+    /* TODO: We need to handle parsing other PID controller configurations.
+     * We can do that by checking for different keys and making the decision
+     * accordingly.
+     */
+    auto p = j.at("pid");
+    p.at("samplePeriod").get_to(c.pidInfo.ts);
+    p.at("proportionalCoeff").get_to(c.pidInfo.proportionalCoeff);
+    p.at("integralCoeff").get_to(c.pidInfo.integralCoeff);
+    p.at("feedFwdOffOffsetCoeff").get_to(c.pidInfo.feedFwdOffset);
+    p.at("feedFwdGainCoeff").get_to(c.pidInfo.feedFwdGain);
+    p.at("integralLimit_min").get_to(c.pidInfo.integralLimit.min);
+    p.at("integralLimit_max").get_to(c.pidInfo.integralLimit.max);
+    p.at("outLim_min").get_to(c.pidInfo.outLim.min);
+    p.at("outLim_max").get_to(c.pidInfo.outLim.max);
+    p.at("slewNeg").get_to(c.pidInfo.slewNeg);
+    p.at("slewPos").get_to(c.pidInfo.slewPos);
+
+    auto positiveHysteresis = p.find("positiveHysteresis");
+    if (positiveHysteresis == p.end())
+    {
+        c.pidInfo.positiveHysteresis = 0.0;
+    }
+    else
+    {
+        j.at("positiveHysteresis").get_to(c.pidInfo.positiveHysteresis);
+    }
+
+    auto negativeHysteresis = p.find("negativeHysteresis");
+    if (negativeHysteresis == p.end())
+    {
+        c.pidInfo.negativeHysteresis = 0.0;
+    }
+    else
+    {
+        j.at("negativeHysteresis").get_to(c.pidInfo.negativeHysteresis);
+    }
+}
+
+std::pair<std::map<int64_t, PIDConf>, std::map<int64_t, struct ZoneConfig>>
+    buildPIDsFromJson(const json& data)
+{
+    // zone -> pids
+    std::map<int64_t, PIDConf> pidConfig;
+    // zone -> configs
+    std::map<int64_t, struct ZoneConfig> zoneConfig;
+
+    /* TODO: if zones is empty, that's invalid. */
+    auto zones = data["zones"];
+    for (const auto& zone : zones)
+    {
+        int64_t id;
+        PIDConf thisZone;
+        struct ZoneConfig thisZoneConfig;
+
+        /* TODO: using at() throws a specific exception we can catch */
+        id = zone["id"];
+        thisZoneConfig.minThermalRpm = zone["minThermalRpm"];
+        thisZoneConfig.failsafePercent = zone["failsafePercent"];
+
+        auto pids = zone["pids"];
+        for (const auto& pid : pids)
+        {
+            auto name = pid["name"];
+            auto item = pid.get<ControllerInfo>();
+
+            thisZone[name] = item;
+        }
+
+        pidConfig[id] = thisZone;
+        zoneConfig[id] = thisZoneConfig;
+    }
+
+    return std::make_pair(pidConfig, zoneConfig);
+}