+ * - Communication is more reliable when the host unconditionally sends
+ * "function codes" (register and waveform indices) in two-digit form.
+ * Device firmware might implement rather specific assumptions.
+ * - Semantics of the right hand side in :rNN= and :bNN= read requests
+ * is uncertain. Just passing 0 in all situations worked in a local
+ * setup. As did omitting the value during interactive exploration.
+ *
+ * Example requests and responses.
+ * - Get model identification (max output frequency)
+ * TX text: --> :r00=0.
+ * TX bytes: --> 3a 72 30 30 3d 30 2e 0d 0a
+ * RX bytes: <-- 3a 72 30 30 3d 36 30 2e 0d 0a
+ * RX text: <-- :r00=60.
+ * - Get all channels' enabled state
+ * TX text: --> :r20=0.
+ * TX bytes: --> 3a 72 32 30 3d 30 2e 0d 0a
+ * RX bytes: <-- 3a 72 32 30 3d 31 2c 31 2e 0d 0a
+ * RX text: <-- :r20=1,1.
+ * - Get first channel's waveform selection
+ * TX text: --> :r21=0.
+ * TX bytes: --> 3a 72 32 31 3d 30 2e 0d 0a
+ * RX bytes: <-- 3a 72 32 31 3d 31 30 33 2e 0d 0a
+ * RX text: <-- :r21=103.
+ * - Set second channel's output frequency
+ * TX text: --> :w24=1234500,0.
+ * TX bytes: --> 3a 77 32 34 3d 31 32 33 34 35 30 30 2c 30 2e 0d 0a
+ * RX bytes: <-- 3a 6f 6b 0d 0a
+ * RX text: <-- :ok
+ * - Read arbitrary waveform number 13
+ * TX text: --> :b13=0.
+ * TX bytes: --> 3a 62 31 33 3d 30 2e 0d 0a
+ * RX bytes: <-- 3a 62 31 33 3d 34 30 39 35 2c 34 30 39 35 2c ... 2c 34 30 39 35 2c 34 30 39 35 2c 0d 0a
+ * RX text: <-- :b13=4095,4095,...,4095,4095,