Understanding Signals with the PropScope - Chapter 5: Synchronous Serial Communication

Andy Lindsay (Parallax)

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sylvie369

Either this one wasn't enabled for comments or I need to learn more about comments in Adobe Reader. Here's some stuff in just plain old text again:

Ch 5 notes:
P. 180-181 – When you talk about the /CS pin, you might consider briefly explaining what the “/” means. This section is written like an introduction to reading pin assignments, and for a beginner, that “/” (or alternatively, a line over the pin name) is a cryptic thing that makes you think you’re missing something. But it’s really easy to understand. The text could be something like
By the way, you might be wondering why there’s a “/” character at the beginning of this pin’s name. “CS” of course stands for “Chip Select”, and the slash indicates “active low”. This means that the chip is selected when this pin is tied to ground (“low&#8221[noparse];)[/noparse], not when it is at the positive Vdd voltage (“high&#8221[noparse];)[/noparse]. In the datasheets for IC devices, a slash character is used to indicate a pin that does something when you connect it to ground. Sometimes “active low” is indicated by a line over the pin’s name instead.
·[noparse][[/noparse]Is that last comment still true? I’m sure I used to see it, but I’m not finding any in a quite look at the datasheets I have here]
·On page 183 you have a little explanation of the “little inverted triangles” in the timing diagram, which seems to me to be at the same level as an explanation of the “/” character in pin diagrams.

P. 181 – The DAC card is referred to as the “DAC CARD” (all caps for both words). Looking back, I see that this is not followed consistently. On pages 43-45 we see both “DAC CARD” and “DAC Card”. I haven’t looked carefully everywhere, but this should have a standard. It’s not clear to me why “CARD” should be in all caps, so I’d prefer “DAC Card”.
P. 183 – “If you send the leftmost digit first and
work your way to the right, you would be sending the values in the most significant bit
first order (MSb first). If you instead work from right to left, you would be sending
values in the least significant bit first (LSB first) order.”
Why “MSb” but “LSB”? That is, why the lowercase “b” in “MSb”?
P. 184 – Step 2:
Send the first clock pulse (a low-high-low signal) to the ADC0831’s CLK
pin, but don’t worry about collecting any data because the ADC0831 just
sends a low signal (the null bit) that doesn’t have any meaning after that first
pulse. The ADC0831 uses the first pulse for its own computations.
That first sentence is kind of convoluted. How about this instead?·
·
Send the first clock pulse (a low-high-low signal) to the ADC0831’s CLK
pin. Don’t worry about collecting any data yet. The ADC0831 just
sends a low signal (the null bit) for its own computations before beginning
the sequence of meaningful pulses.
·
Steps 1 and 6 need a period at the end.
·
P. 185:
·
Although ADC0831Test1.bs2 might not seem optimized from the PBASIC programming
standpoint, it’s still a useful exercise. Not all microcontroller programming languages
have built-in commands that automate synchronous serial communication. So
ADC0831Test1.bs2 provides an example that utilizes lower level commands to
implement a timing diagram.
·
How about something like this?
·
ADC0831Test1.bs2 might seem inefficient and complicated from the PBASIC programming standpoint. In fact, PBASIC has a pair of commands named SHIFTIN and SHIFTOUT that automatically do most of this work for you in a single line of code. However, it’s still a useful exercise. Not all microcontroller programming languages have built-in commands that automate synchronous serial communication. ADC0831Test1.bs2 shows you how to use lower level commands to implement a timing diagram.
·
I see that you do introduce SHIFTIN and SHIFTOUT later, but I don’t think that this change will affect that.
·
Later: ACTIVITY #3: VERIFY MICROCONTROLLER SIGNALLING
·
Should be “Signaling” (only one “l&#8221[noparse];)[/noparse].
·
P. 186 top: “This voltage increment is just enough to make its measurement step
from 0 t 1”
·
Should be “From 0 to 1”
·
“and it depends on the range of voltage the device is configured to measure”
·
How about “and the size of the increment depends on the range of the voltage the device is configured to measure”?
·
Later : you have both “LSB” and “LSb” mixed here. The equations have V_LSb, while the discussion around them have V_LSB. Later equations have V_LSB.
·
In the box: “If you see the term quantize in A/D converter documentation, it means that an analog to digital converter”
·
How about quotes around “quantize”?
·
P. 188 – You have
·
“Remember that the potentiometer’s
wiper terminal output voltage is connected to the ADC0831’s Vin(+) pin as well as to the
PropScope’s CH1 probe. So we can use the Oscilloscope to verify the voltage the
potentiometer applies to the ADC0831’s Vin(+) pin.”
·
This is something that occurs in a number of places in the document, including once earlier in this chapter, and at least once in other chapters. It’s not a big deal, and you may choose to leave it as is, but technically that second sentence is a sentence fragment. “So” should be used after a comma to connect parts of a sentence, not as an introduction to the next sentence. Now, given the informal tone of the entire document, I think you shouldn’t change this, but I thought I’d mention it at least.
·
P. 197 :
·
“The “best” version uses a PBASIC command called SHIFTIN to complete the operation, including a fist null pulse, in a single command.”
·
Er, how about “first”?
·
I REALLY love this demonstration of the difference between the time taken to do this one step at a time and the time taken to do it with SHIFTIN.
·
On P. 191 you have “Trouble-Shooting” in the section title. On P. 201 you have “trouble shooting” (two words, no hyphen). You should decide on a standard for this. I don’t know if there’s a rule, but consistency would be good. On P. 204 you have “trouble-shoot”.
·
P. 203 – “A variety of inexpensive, special purpose integrated circuits are available to perform
tasks like memory storage, co processing”
·
How about “co-processing” or “coprocessing”? I think either is fine, though consistency would be important here as well.
·
P. 204 Exercise #1: “Calculate the value the it is transmitting.”
How about “Calculate the value that it is transmitting.” ?
·
P. 205 – there appear to be extra tabs at the start of answers #10 and 11.

Post Edited (sylvie369) : 7/29/2010 10:59:11 PM GMT