TTL USB dongle to 5V TTL serial.
This is not a RS232 USB dongle which has it's own issues with interfacing to older equipment (but same problem, no enough current to push or pull the signal). I have a 3v3/5v0 USB TTL dongle. It works with some equipment but it couldn't pull the signal to 5v0 interfacing to my HD6303 (Hitachi's 6803). I fixed this by using 2 gates on a 74LS04 with the USB dongles TX. Not sure how to solve this. Has anyone built such a set of line drivers? I'll be using a similar setup with a few other boards (EPROM burner, PT69-5, Microbox II, etc.). But those might be worse as I'll be using a ESP WiFi chip (3v3) as a terminal server. -- Linux Home Automation Neil Cherry kd2zrq@linuxha.com http://www.linuxha.com/ Main site http://linuxha.blogspot.com/ My HA Blog Author of: Linux Smart Homes For Dummies KD2ZRQ
I'm not positive what the question is but since nobody else replied yet I'll take a shot. I have made various signal level convertes in the past. If you want true 5V high you need to use a CMOS chip. If coming from TTL or 3.3V CMOS you need TTL input threshold device such as 74HCT. That give about rail at 20uA or .7 drop at 4mA. 74ACT is .8V drop at 24mA so will give better high level under load. On Thu, Feb 16, 2023 at 10:04:20AM -0500, Neil Cherry via vcf-midatlantic wrote:
This is not a RS232 USB dongle which has it's own issues with interfacing to older equipment (but same problem, no enough current to push or pull the signal).
I have a 3v3/5v0 USB TTL dongle. It works with some equipment but it couldn't pull the signal to 5v0 interfacing to my HD6303 (Hitachi's 6803). I fixed this by using 2 gates on a 74LS04 with the USB dongles TX.
Not sure how to solve this. Has anyone built such a set of line drivers?
I'll be using a similar setup with a few other boards (EPROM burner, PT69-5, Microbox II, etc.). But those might be worse as I'll be using a ESP WiFi chip (3v3) as a terminal server.
-- Linux Home Automation Neil Cherry kd2zrq@linuxha.com http://www.linuxha.com/ Main site http://linuxha.blogspot.com/ My HA Blog Author of: Linux Smart Homes For Dummies KD2ZRQ
On 2/16/23 16:38, David Gesswein via vcf-midatlantic wrote:
I'm not positive what the question is but since nobody else replied yet I'll take a shot. I have made various signal level convertes in the past. If you want true 5V high you need to use a CMOS chip. If coming from TTL or 3.3V CMOS you need TTL input threshold device such as 74HCT. That give about rail at 20uA or .7 drop at 4mA. 74ACT is .8V drop at 24mA so will give better high level under load.
Basically I'm looking to build some kind of standard board to allow me to use the USB TTL dongle (CH341) to hook up to my vintage computers without having to go '3v3/5v0 TTL' to RS232 back down to 5v0 TTL. I tried the Adafruit converter but it didn't have the current to drive the serial into the HD6303. On another mail list someone has suggested looking at CD74HC4049 and CD74HC405. I forgot about those chips. Some of the more interesting chips are 16 bits wide. A bit (14) more than I need. The good news is that the 74LS04 is working nicely. I've got the 8K RAM added and I'm writing 6801 asm code. These LEDs are driven in a strange way. The 2 - 7 Segmented LEDs and the 7 individual LEDs are driven by the same 8 bits. -- Linux Home Automation Neil Cherry kd2zrq@linuxha.com http://www.linuxha.com/ Main site http://linuxha.blogspot.com/ My HA Blog Author of: Linux Smart Homes For Dummies KD2ZRQ
I have used a MAX232 for this purpose https://www.ti.com/lit/ds/symlink/max232.pdf It’s a TTL to RS232 driver. I thought that’s what you were using when you showed me on Friday. Iirc you have to put a few charge capacitors on the 232 side to raise it up to the required 12 volts I just ordered a bunch of parts from digi if I had known you needed some I would have grabbed a few. I try to pack the box as much as possible to save on shipping since it’s a flat 8 dollars over 14 ounces. -Ian L. On Thu, Feb 16, 2023 at 23:37 Neil Cherry via vcf-midatlantic < vcf-midatlantic@lists.vcfed.org> wrote:
On 2/16/23 16:38, David Gesswein via vcf-midatlantic wrote:
I'm not positive what the question is but since nobody else replied yet I'll take a shot. I have made various signal level convertes in the past. If you want true 5V high you need to use a CMOS chip. If coming from TTL or 3.3V CMOS you need TTL input threshold device such as 74HCT. That give about rail at 20uA or .7 drop at 4mA. 74ACT is .8V drop at 24mA so will give better high level under load.
Basically I'm looking to build some kind of standard board to allow me to use the USB TTL dongle (CH341) to hook up to my vintage computers without having to go '3v3/5v0 TTL' to RS232 back down to 5v0 TTL.
I tried the Adafruit converter but it didn't have the current to drive the serial into the HD6303.
On another mail list someone has suggested looking at CD74HC4049 and CD74HC405. I forgot about those chips.
Some of the more interesting chips are 16 bits wide. A bit (14) more than I need.
The good news is that the 74LS04 is working nicely. I've got the 8K RAM added and I'm writing 6801 asm code. These LEDs are driven in a strange way. The 2 - 7 Segmented LEDs and the 7 individual LEDs are driven by the same 8 bits.
-- Linux Home Automation Neil Cherry kd2zrq@linuxha.com http://www.linuxha.com/ Main site http://linuxha.blogspot.com/ My HA Blog Author of: Linux Smart Homes For Dummies KD2ZRQ
Oh wait, I misread you are trying to go from 3.3 to 5v TTL not to RS232. Right there isn’t enough drive from the FTDI clone to drive the remote serial interface. I would pick up a proper 5v FTDI the clones like the CH341, at 3.3 are unreliable in my experience https://www.amazon.com/Sparkfun-Electronics-4446819-FTDI-Cable/dp/B00DJBNDHE I am pretty sure I have one we can test with on Sunday/Monday before you go out an buy one. But I do fully recommend a proper FTDI -Ian L. On Fri, Feb 17, 2023 at 04:42 Ian Litchfield <kd2ixl@gmail.com> wrote:
I have used a MAX232 for this purpose
https://www.ti.com/lit/ds/symlink/max232.pdf
It’s a TTL to RS232 driver. I thought that’s what you were using when you showed me on Friday. Iirc you have to put a few charge capacitors on the 232 side to raise it up to the required 12 volts
I just ordered a bunch of parts from digi if I had known you needed some I would have grabbed a few. I try to pack the box as much as possible to save on shipping since it’s a flat 8 dollars over 14 ounces.
-Ian L.
On Thu, Feb 16, 2023 at 23:37 Neil Cherry via vcf-midatlantic < vcf-midatlantic@lists.vcfed.org> wrote:
On 2/16/23 16:38, David Gesswein via vcf-midatlantic wrote:
I'm not positive what the question is but since nobody else replied yet I'll take a shot. I have made various signal level convertes in the past. If you want true 5V high you need to use a CMOS chip. If coming from TTL or 3.3V CMOS you need TTL input threshold device such as 74HCT. That give about rail at 20uA or .7 drop at 4mA. 74ACT is .8V drop at 24mA so will give better high level under load.
Basically I'm looking to build some kind of standard board to allow me to use the USB TTL dongle (CH341) to hook up to my vintage computers without having to go '3v3/5v0 TTL' to RS232 back down to 5v0 TTL.
I tried the Adafruit converter but it didn't have the current to drive the serial into the HD6303.
On another mail list someone has suggested looking at CD74HC4049 and CD74HC405. I forgot about those chips.
Some of the more interesting chips are 16 bits wide. A bit (14) more than I need.
The good news is that the 74LS04 is working nicely. I've got the 8K RAM added and I'm writing 6801 asm code. These LEDs are driven in a strange way. The 2 - 7 Segmented LEDs and the 7 individual LEDs are driven by the same 8 bits.
-- Linux Home Automation Neil Cherry kd2zrq@linuxha.com http://www.linuxha.com/ Main site http://linuxha.blogspot.com/ My HA Blog Author of: Linux Smart Homes For Dummies KD2ZRQ
participants (3)
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David Gesswein -
Ian Litchfield -
Neil Cherry