开云体育

Display driver board reality

K9HZ All Messages By This Member #32606 开云体育 Oh brother, this is starting to get complicated. ? The RA8875 is a 3.3V chip… and the inputs, as far as I can tell… from my research so far… are only 3.3V tolerant.?? ? To make this more confusing, some of the display.com displays have level shifting hardware onboard that you can enable to use the display as a 3.3V display or as a 5V display (in line with the power selections on the MAIN board).? However, not all do (particularly the smaller displays). ?The boards I made work with 3.3V and 5V display boards… which is fine for 3.3V operation for all display boards…. The problem comes if you select 5V operation bon the MAIN board… but either don’t have a 5V control line selection on the display board for level change to 3.3V for the RA8875… or if you DO have the level change hardware on your display board but have not selected it.? In this case, you will destroy the RA8875 chip. ? I can do two things.? One is to put together a list of all the approved Display.com display part numbers (upper middle of the back of the display) and give guidance on what you need to do so that the display continues to function with this driver board.? The other thing I can do is make a second board that has a tiny 3.3V regulator on it to power the three control lines to just 3.3V in the case of running the display off 5V but no hardware is there for level shifting the data lines to 3.3V. ? Comments? ?????? ? ? Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ ? Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois ? Owner – Operator Villa Grand Piton – J68HZ Soufriere, St. Lucia W.I. Rent it: ? Moderator: North American QRO Group at Groups.IO. Moderator: Amateur Radio Builders Group at Groups.IO. ? email:? bill@... ? ?
jerry-KF6VB All Messages By This Member #32607 My understanding is the the 5" board is 3v3 - period. The 5V option just sticks a 3-terminal regulator on the board to make 5V supply into 3v3 for the internals. I used the 5V option because I figured that it would be a little easier on my main board regulators - even though they're switching - and because I thought the on-board 3v3 3-terminal regulator would get me a little noise reduction on the main board bus. It's working fine - except for when I hold my handi-talkie up to it & transmit. - Jerry toggle quoted message Show quoted text On 2025-02-06 11:29, K9HZ wrote: Oh brother, this is starting to get complicated. The RA8875 is a 3.3V chip… and the inputs, as far as I can tell… from my research so far… are only 3.3V tolerant. To make this more confusing, some of the display.com displays have level shifting hardware onboard that you can enable to use the display as a 3.3V display or as a 5V display (in line with the power selections on the MAIN board). However, not all do (particularly the smaller displays). The boards I made work with 3.3V and 5V display boards… which is fine for 3.3V operation for all display boards…. The problem comes if you select 5V operation bon the MAIN board… but either don't have a 5V control line selection on the display board for level change to 3.3V for the RA8875… or if you DO have the level change hardware on your display board but have not selected it. In this case, you will destroy the RA8875 chip. I can do two things. One is to put together a list of all the approved Display.com display part numbers (upper middle of the back of the display) and give guidance on what you need to do so that the display continues to function with this driver board. The other thing I can do is make a second board that has a tiny 3.3V regulator on it to power the three control lines to just 3.3V in the case of running the display off 5V but no hardware is there for level shifting the data lines to 3.3V. Comments? DR. WILLIAM J. SCHMIDT - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ Owner - Operator Big Signal Ranch - K9ZC Staunton, Illinois Owner - Operator Villa Grand Piton - J68HZ Soufriere, St. Lucia W.I. Rent it: www.VillaGrandPiton.com [1] Moderator: North American QRO Group at Groups.IO. Moderator: Amateur Radio Builders Group at Groups.IO. email: bill@... Links: ------ [1] [2] /g/SoftwareControlledHamRadio/message/32606 [3] /mt/111038971/243852 [4] /g/SoftwareControlledHamRadio/post [5] /g/SoftwareControlledHamRadio/editsub/243852 [6] /g/SoftwareControlledHamRadio/leave/10484476/243852/1943518115/xyzzy
Terrance Robertson, KN6ZDE All Messages By This Member #32608 I have a number of these displays (both 5" and 7").? All can either run on 3.3 or 5V with jumper change (they all have a 3.3V regulator for 5V operation).? All are only 3.3V on the data lines, no level converters.
K9HZ All Messages By This Member #32609 开云体育 Yep that’s what I found… ? ? Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ ? Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois ? Owner – Operator Villa Grand Piton – J68HZ Soufriere, St. Lucia W.I. Rent it: ? Moderator: North American QRO Group at Groups.IO. Moderator: Amateur Radio Builders Group at Groups.IO. ? email:? bill@... ? ? toggle quoted message Show quoted text From: [email protected] <[email protected]> On Behalf Of Terrance Robertson, KN6ZDE via groups.io Sent: Thursday, February 6, 2025 6:31 PM To: [email protected] Subject: Re: [SoftwareControlledHamRadio] Display driver board reality ? I have a number of these displays (both 5" and 7").? All can either run on 3.3 or 5V with jumper change (they all have a 3.3V regulator for 5V operation).? All are only 3.3V on the data lines, no level converters.
bruce williams All Messages By This Member #32616 Just a thought but I am no EE.? I like the guidance and list.? The only remaining issue is? ? or if you DO have the level change hardware on your display board but have not selected it ? Is it not possible to use a 3.3v zener to clamp and protect this.? This would prevent from destroying the RA8875.? ?It may be the circuit would not function properly if the zener clamps, but at least the RA chip would not be destroyed.? Then the builder can resolve by selecting the level change. ? Maybe it helps, maybe not ?
jerry-KF6VB All Messages By This Member #32620 On 2025-02-07 08:20, bruce williams via groups.io wrote: Just a thought but I am no EE. I like the guidance and list. The only remaining issue is _OR IF YOU DO HAVE THE LEVEL CHANGE HARDWARE ON YOUR DISPLAY BOARD BUT HAVE NOT SELECTED IT_ Is it not possible to use a 3.3v zener to clamp and protect this. *** To make protection complete, use a 3.3V zener and a fuse. Goof up, the fuse blows, you fix the problem and replace the fuse. Might want to use a zener slightly higher V, so it doesn't interfere with normal operations. The RA8875 is worth protecting. I replaced one. Not fun. - Jerry, KF6VB
K9HZ All Messages By This Member #32621 开云体育 Not quite that simple… Some, but few zeners operate at 10 MHz like the SPI clock and data signal lines do.? What you get instead is something that looks like a mountain shaped waveform.? People have learned this the hard way thinking they can use them as boas clipping diodes on RF transistors only to find that the transistors still blow up. ? ? Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ ? Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois ? Owner – Operator Villa Grand Piton – J68HZ Soufriere, St. Lucia W.I. Rent it: ? Moderator: North American QRO Group at Groups.IO. Moderator: Amateur Radio Builders Group at Groups.IO. ? email:? bill@... ? ? toggle quoted message Show quoted text From: [email protected] <[email protected]> On Behalf Of bruce williams via groups.io Sent: Friday, February 7, 2025 10:20 AM To: [email protected] Subject: Re: [SoftwareControlledHamRadio] Display driver board reality ? Just a thought but I am no EE.? I like the guidance and list.? The only remaining issue is? ? *or if you DO have the level change hardware on your display board but have not selected it* ? Is it not possible to use a 3.3v zener to clamp and protect this.? This would prevent from destroying the RA8875.? ?It may be the circuit would not function properly if the zener clamps, but at least the RA chip would not be destroyed.? Then the builder can resolve by selecting the level change. ? Maybe it helps, maybe not ?
Phil Taylor All Messages By This Member #32623 Well here are the logic levels in the Spec sheet ? ? VDDIO is clearly 3.3V, Max voltage 3.6. VDDIO Hi and 0.2VDDIO Low.? ? ? Regards Phil VK2KKZ
K9HZ All Messages By This Member #32624 开云体育 For that display… yes. ? ? Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ ? Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois ? Owner – Operator Villa Grand Piton – J68HZ Soufriere, St. Lucia W.I. Rent it: ? Moderator: North American QRO Group at Groups.IO. Moderator: Amateur Radio Builders Group at Groups.IO. ? email:? bill@... ? ? toggle quoted message Show quoted text From: [email protected] <[email protected]> On Behalf Of Phil Taylor via groups.io Sent: Friday, February 7, 2025 2:26 PM To: [email protected] Subject: Re: [SoftwareControlledHamRadio] Display driver board reality ? Well here are the logic levels in the Spec sheet ? ? VDDIO is clearly 3.3V, Max voltage 3.6. VDDIO Hi and 0.2VDDIO Low.? ? ? Regards Phil VK2KKZ
Phil Taylor All Messages By This Member #32632 Also for the 5" version... ? ? ? ? Regards Phil VK2KKZ

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