shortened i2c "magnetometer" and "accelerometer" commands

Author: BartMassey

mdbook/src/11-i2c/src/main.rs

@@ -74,14 +74,14 @@ fn main() -> ! {
             }
         }
 
-        if str::from_utf8(&buffer).unwrap().trim() == "accelerometer" {
+        if str::from_utf8(&buffer).unwrap().trim() == "acc" {
             while !sensor.accel_status().unwrap().xyz_new_data() {
                 timer0.delay_ms(1u32);
             }
 
             let (x, y, z) = sensor.acceleration().unwrap().xyz_mg();
             write!(serial, "Accelerometer: x {} y {} z {}\r\n", x, y, z).unwrap();
-        } else if str::from_utf8(&buffer).unwrap().trim() == "magnetometer" {
+        } else if str::from_utf8(&buffer).unwrap().trim() == "mag" {
             while !sensor.mag_status().unwrap().xyz_new_data() {
                 timer0.delay_ms(1u32);
             }

mdbook/src/11-i2c/the-challenge.md

@@ -1,11 +1,11 @@
 # The challenge
 
-The challenge for this chapter is, to build a small application that
-communicates with the outside world via the serial interface introduced
-in the last chapter. It should be able to receive the commands "magnetometer"
-as well as "accelerometer" and then print the corresponding sensor data
-in response. This time no template code will be provided since all you need
-is already provided in the [UART](../10-uart/index.md) and this chapter. However, here are a few clues:
+The challenge for this chapter is, to build a small application that communicates with the outside
+world via the serial interface introduced in the last chapter. It should be able to receive the
+commands "mag" for magnetometer as well as "acc" for accelerometer. It should then print the
+corresponding sensor data to the serial port in response. This time no template code will be
+provided since all you need is already provided in the [UART](../10-uart/index.md) and this
+chapter. However, here are a few clues:
 
--   You might be interested in `core::str::from_utf8` to convert the bytes in the buffer to a `&str`, since we need to compare with `"magnetometer"` and `"accelerometer"`.
+-   You might be interested in `core::str::from_utf8` to convert the bytes in the buffer to a `&str`, since we need to compare with `"mag"` and `"acc"`.
 -   You will have to read the documentation for the magnetometer API and functionality. While the `lsm303agr` crate provides the API interface, the [LSM303AGR datasheet](https://www.st.com/resource/en/datasheet/lsm303agr.pdf) details the sensor's magnetic field measurement parameters. See pages 13-15 for sensor characteristics and, importantly, pages 66-67 for the output register format.