README: Update instruction on finding Rust version

README.md

@@ -23,7 +23,7 @@ cargo build --release
 
 The resulting ELF file will be located under `target/thumbv7em-none-eabihf/release/thermostat`.
 
-Alternatively, you can install the Rust toolchain without Nix using rustup; see the Rust manifest file pulled in `flake.nix` to determine which Rust version to use.
+Alternatively, you can install the Rust toolchain without Nix using rustup; see the `rust` variable in `flake.nix` to determine which Rust version to use.
 
 ## Debugging
 
@@ -94,7 +94,7 @@ formatted as line-delimited JSON.
 
 | Syntax                                     | Function                                                                      |
 |------------------------------------------- |-------------------------------------------------------------------------------|
-| `report`                                   | Show current input                                                            |
+| `report`                                   | Show latest report of channel parameters (see *Reports* section)              |
 | `pwm`                                      | Show current PWM settings                                                     |
 | `pwm <0/1> max_i_pos <amp>`                | Set maximum positive output current, clamped to [0, 2]                        |
 | `pwm <0/1> max_i_neg <amp>`                | Set maximum negative output current, clamped to [0, 2]                        |
@@ -189,7 +189,7 @@ Testing heat flow direction with a low set current is recommended before install
 
 ### Limits
 
-Each of the MAX1968 TEC driver has analog/PWM inputs for setting
+Each MAX1968 TEC driver has analog/PWM inputs for setting
 output limits.
 
 Use the `pwm` command to see current settings and maximum values.
@@ -218,7 +218,7 @@ pwm 0 max_i_pos 3
 
 ### Open-loop mode
 
-To manually control TEC output current, omit the limit parameter of
+To manually control TEC output current, set a fixed output current with
 the `pwm` command. Doing so will disengage the PID control for that
 channel.
 
@@ -257,6 +257,7 @@ with the following keys.
 | ---            | :---:           | ---                                                  |
 | `channel`      | Integer         | Channel `0`, or `1`                                  |
 | `time`         | Seconds         | Temperature measurement time                         |
+| `interval`     | Seconds         | Time elapsed since last report update on channel     |
 | `adc`          | Volts           | AD7172 input                                         |
 | `sens`         | Ohms            | Thermistor resistance derived from `adc`             |
 | `temperature`  | Degrees Celsius | Steinhart-Hart conversion result derived from `sens` |
@@ -269,7 +270,7 @@ with the following keys.
 | `tec_u_meas`   | Volts           | Measurement of the voltage across the TEC            |
 | `pid_output`   | Amperes         | PID control output                                   |
 
-Note: With Thermostat v2 and below, the voltage and current readouts `i_tec` and `tec_i` are noisy without the hardware fix shown in [this PR][https://git.m-labs.hk/M-Labs/thermostat/pulls/105].
+Note: Prior to Thermostat hardware revision v2.2.4, the voltage and current readouts `i_tec` and `tec_i` are noisy without the hardware fix shown in [this PR](https://git.m-labs.hk/M-Labs/thermostat/pulls/105).
 
 ## PID Tuning