Why is there a diode on the RX pin of the Adafruit Ultimate GPS board?
I can't seem to understand why there is a diode at the Rx pin on this Adafruit Ultimate GPS board. If we are sending data to the GPS, why put a diode that prevents current flow into this pin?
diodes uart gps
asked 5 hours ago
YNGVVYNGVV
164
add a comment |
I can't seem to understand why there is a diode at the Rx pin on this Adafruit Ultimate GPS board. If we are sending data to the GPS, why put a diode that prevents current flow into this pin?
diodes uart gps
asked 5 hours ago
YNGVVYNGVV
164
1
Are you referring to D1? Did you read the note in the schematic telling you what it's for?
– brhans
5 hours ago
add a comment |
I can't seem to understand why there is a diode at the Rx pin on this Adafruit Ultimate GPS board. If we are sending data to the GPS, why put a diode that prevents current flow into this pin?
diodes uart gps
asked 5 hours ago
YNGVVYNGVV
164
I can't seem to understand why there is a diode at the Rx pin on this Adafruit Ultimate GPS board. If we are sending data to the GPS, why put a diode that prevents current flow into this pin?
diodes uart gps
diodes uart gps
asked 5 hours ago
YNGVVYNGVV
164
asked 5 hours ago
YNGVVYNGVV
164
asked 5 hours ago
YNGVVYNGVV
164
asked 5 hours ago
YNGVVYNGVV
164
asked 5 hours ago
YNGVVYNGVV
164
164
1
Are you referring to D1? Did you read the note in the schematic telling you what it's for?
– brhans
5 hours ago
add a comment |
1
Are you referring to D1? Did you read the note in the schematic telling you what it's for?
– brhans
5 hours ago
1
1
Are you referring to D1? Did you read the note in the schematic telling you what it's for?
– brhans
5 hours ago
Are you referring to D1? Did you read the note in the schematic telling you what it's for?
– brhans
5 hours ago
add a comment |
2 Answers
2
active
oldest
votes
The pull-up resistor to 3.3V and the diode means that even if you feed the circuit with 5V logic (most Arduino boards use 5V logic) the GPS chipset will see a maximum of 3.3v. The MT3339 device may be damaged or operate incorrectly if any of its pins go above its 3.3V supply rail.
If the signal RX_5V goes to a logic low the diode will conduct and pull the MT3339 RX pin to ~0.7V that it will treat as a logic low.
If RX_5V goes to 5V resistor R3 will pull the MT3339 RX up to 3.3V and the diode will be reverse biased.
answered 5 hours ago
Kevin WhiteKevin White
12.8k11521
and that sir is the answer!!!
– Edwin Fairchild
17 mins ago
add a comment |
The purpose of the diode is documented in a line of text near it on the schematic. The diode and resistor protect the RX input.
answered 5 hours ago
Elliot AldersonElliot Alderson
5,3101918
I should have elaborated. Yes, I see the note on the schematic and see that if a voltage higher than 3.3V is at RX_5V then current will be blocked by D1. But I do not understand how this allows any data to be transferred to the Rx pin if D1 is blocking all current flow from RX_5V. Could it be that if RX_5V is grounded/low/off, then RX will read 0 and if RX_5V is high (~3.3V or greater), RX will read 1 while being protected from any signal >3.3V? EDIT: Just saw @Kevin White's follow-up. Thanks!
– YNGVV
5 hours ago
add a comment |
Your Answer
StackExchange.ifUsing("editor", function () {
return StackExchange.using("mathjaxEditing", function () {
StackExchange.MarkdownEditor.creationCallbacks.add(function (editor, postfix) {
StackExchange.mathjaxEditing.prepareWmdForMathJax(editor, postfix, [["\$", "\$"]]);
});
});
}, "mathjax-editing");
StackExchange.ifUsing("editor", function () {
return StackExchange.using("schematics", function () {
StackExchange.schematics.init();
});
}, "cicuitlab");
StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "135"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);
StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});
function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: false,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: null,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});
}
});
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2felectronics.stackexchange.com%2fquestions%2f416670%2fwhy-is-there-a-diode-on-the-rx-pin-of-the-adafruit-ultimate-gps-board%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
The pull-up resistor to 3.3V and the diode means that even if you feed the circuit with 5V logic (most Arduino boards use 5V logic) the GPS chipset will see a maximum of 3.3v. The MT3339 device may be damaged or operate incorrectly if any of its pins go above its 3.3V supply rail.
If the signal RX_5V goes to a logic low the diode will conduct and pull the MT3339 RX pin to ~0.7V that it will treat as a logic low.
If RX_5V goes to 5V resistor R3 will pull the MT3339 RX up to 3.3V and the diode will be reverse biased.
answered 5 hours ago
Kevin WhiteKevin White
12.8k11521
and that sir is the answer!!!
– Edwin Fairchild
17 mins ago
add a comment |
The pull-up resistor to 3.3V and the diode means that even if you feed the circuit with 5V logic (most Arduino boards use 5V logic) the GPS chipset will see a maximum of 3.3v. The MT3339 device may be damaged or operate incorrectly if any of its pins go above its 3.3V supply rail.
If the signal RX_5V goes to a logic low the diode will conduct and pull the MT3339 RX pin to ~0.7V that it will treat as a logic low.
If RX_5V goes to 5V resistor R3 will pull the MT3339 RX up to 3.3V and the diode will be reverse biased.
answered 5 hours ago
Kevin WhiteKevin White
12.8k11521
and that sir is the answer!!!
– Edwin Fairchild
17 mins ago
add a comment |
The pull-up resistor to 3.3V and the diode means that even if you feed the circuit with 5V logic (most Arduino boards use 5V logic) the GPS chipset will see a maximum of 3.3v. The MT3339 device may be damaged or operate incorrectly if any of its pins go above its 3.3V supply rail.
If the signal RX_5V goes to a logic low the diode will conduct and pull the MT3339 RX pin to ~0.7V that it will treat as a logic low.
If RX_5V goes to 5V resistor R3 will pull the MT3339 RX up to 3.3V and the diode will be reverse biased.
answered 5 hours ago
Kevin WhiteKevin White
12.8k11521
The pull-up resistor to 3.3V and the diode means that even if you feed the circuit with 5V logic (most Arduino boards use 5V logic) the GPS chipset will see a maximum of 3.3v. The MT3339 device may be damaged or operate incorrectly if any of its pins go above its 3.3V supply rail.
If the signal RX_5V goes to a logic low the diode will conduct and pull the MT3339 RX pin to ~0.7V that it will treat as a logic low.
If RX_5V goes to 5V resistor R3 will pull the MT3339 RX up to 3.3V and the diode will be reverse biased.
answered 5 hours ago
Kevin WhiteKevin White
12.8k11521
edited 1 hour ago
answered 5 hours ago
Kevin WhiteKevin White
12.8k11521
answered 5 hours ago
Kevin WhiteKevin White
12.8k11521
answered 5 hours ago
Kevin WhiteKevin White
12.8k11521
12.8k11521
and that sir is the answer!!!
– Edwin Fairchild
17 mins ago
add a comment |
and that sir is the answer!!!
– Edwin Fairchild
17 mins ago
and that sir is the answer!!!
– Edwin Fairchild
17 mins ago
and that sir is the answer!!!
– Edwin Fairchild
17 mins ago
add a comment |
The purpose of the diode is documented in a line of text near it on the schematic. The diode and resistor protect the RX input.
answered 5 hours ago
Elliot AldersonElliot Alderson
5,3101918
I should have elaborated. Yes, I see the note on the schematic and see that if a voltage higher than 3.3V is at RX_5V then current will be blocked by D1. But I do not understand how this allows any data to be transferred to the Rx pin if D1 is blocking all current flow from RX_5V. Could it be that if RX_5V is grounded/low/off, then RX will read 0 and if RX_5V is high (~3.3V or greater), RX will read 1 while being protected from any signal >3.3V? EDIT: Just saw @Kevin White's follow-up. Thanks!
– YNGVV
5 hours ago
add a comment |
The purpose of the diode is documented in a line of text near it on the schematic. The diode and resistor protect the RX input.
answered 5 hours ago
Elliot AldersonElliot Alderson
5,3101918
I should have elaborated. Yes, I see the note on the schematic and see that if a voltage higher than 3.3V is at RX_5V then current will be blocked by D1. But I do not understand how this allows any data to be transferred to the Rx pin if D1 is blocking all current flow from RX_5V. Could it be that if RX_5V is grounded/low/off, then RX will read 0 and if RX_5V is high (~3.3V or greater), RX will read 1 while being protected from any signal >3.3V? EDIT: Just saw @Kevin White's follow-up. Thanks!
– YNGVV
5 hours ago
add a comment |
The purpose of the diode is documented in a line of text near it on the schematic. The diode and resistor protect the RX input.
answered 5 hours ago
Elliot AldersonElliot Alderson
5,3101918
The purpose of the diode is documented in a line of text near it on the schematic. The diode and resistor protect the RX input.
answered 5 hours ago
Elliot AldersonElliot Alderson
5,3101918
answered 5 hours ago
Elliot AldersonElliot Alderson
5,3101918
answered 5 hours ago
Elliot AldersonElliot Alderson
5,3101918
answered 5 hours ago
Elliot AldersonElliot Alderson
5,3101918
5,3101918
I should have elaborated. Yes, I see the note on the schematic and see that if a voltage higher than 3.3V is at RX_5V then current will be blocked by D1. But I do not understand how this allows any data to be transferred to the Rx pin if D1 is blocking all current flow from RX_5V. Could it be that if RX_5V is grounded/low/off, then RX will read 0 and if RX_5V is high (~3.3V or greater), RX will read 1 while being protected from any signal >3.3V? EDIT: Just saw @Kevin White's follow-up. Thanks!
– YNGVV
5 hours ago
add a comment |
I should have elaborated. Yes, I see the note on the schematic and see that if a voltage higher than 3.3V is at RX_5V then current will be blocked by D1. But I do not understand how this allows any data to be transferred to the Rx pin if D1 is blocking all current flow from RX_5V. Could it be that if RX_5V is grounded/low/off, then RX will read 0 and if RX_5V is high (~3.3V or greater), RX will read 1 while being protected from any signal >3.3V? EDIT: Just saw @Kevin White's follow-up. Thanks!
– YNGVV
5 hours ago
I should have elaborated. Yes, I see the note on the schematic and see that if a voltage higher than 3.3V is at RX_5V then current will be blocked by D1. But I do not understand how this allows any data to be transferred to the Rx pin if D1 is blocking all current flow from RX_5V. Could it be that if RX_5V is grounded/low/off, then RX will read 0 and if RX_5V is high (~3.3V or greater), RX will read 1 while being protected from any signal >3.3V? EDIT: Just saw @Kevin White's follow-up. Thanks!
– YNGVV
5 hours ago
I should have elaborated. Yes, I see the note on the schematic and see that if a voltage higher than 3.3V is at RX_5V then current will be blocked by D1. But I do not understand how this allows any data to be transferred to the Rx pin if D1 is blocking all current flow from RX_5V. Could it be that if RX_5V is grounded/low/off, then RX will read 0 and if RX_5V is high (~3.3V or greater), RX will read 1 while being protected from any signal >3.3V? EDIT: Just saw @Kevin White's follow-up. Thanks!
– YNGVV
5 hours ago
add a comment |
Thanks for contributing an answer to Electrical Engineering Stack Exchange!
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
Use MathJax to format equations. MathJax reference.
To learn more, see our tips on writing great answers.
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2felectronics.stackexchange.com%2fquestions%2f416670%2fwhy-is-there-a-diode-on-the-rx-pin-of-the-adafruit-ultimate-gps-board%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
1
Are you referring to D1? Did you read the note in the schematic telling you what it's for?
– brhans
5 hours ago