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SiriusHardware · 26th Apr 2020, 6:37 pm

If you are convinced that the problem is RS232 levels / voltages then I would consider bypassing the onboard level converters in your gadget with a MAX232, since that has charge pump circuitry onboard to make +/- 10V from 5V as far as I remember. You can get tiny ready made level converters with an SMD MAX232 onboard. Unfortunately all the ones I can readily find are on ebay so I can't point you directly to one particular listing but if you search on

"Mini-Level-Converter-RS232-to-TTL-Adapter-Module-MAX3232-MAX232-Serial-Board"

The ones where the PCB is barely bigger than the SMD chip are the ones I'm talking about. So small, you can fit one inside almost anything. So cheap, it's hardly worth making one yourself.

It's definitely the gadget not receiving, rather than the RS232 source not sending? I'm just wondering if the source is expecting to see hardware or software handshaking before it will send? You may just need to strap two or three of the pins together inside the 'D' plug which is plugged into the USB-RS232 lead.

26th Apr 2020, 6:37 pm	#22
SiriusHardware Dekatron Join Date: Aug 2011 Location: Newcastle, Tyne and Wear, UK. Posts: 11,586	Re: Maplin Z80 SBC If you are convinced that the problem is RS232 levels / voltages then I would consider bypassing the onboard level converters in your gadget with a MAX232, since that has charge pump circuitry onboard to make +/- 10V from 5V as far as I remember. You can get tiny ready made level converters with an SMD MAX232 onboard. Unfortunately all the ones I can readily find are on ebay so I can't point you directly to one particular listing but if you search on "Mini-Level-Converter-RS232-to-TTL-Adapter-Module-MAX3232-MAX232-Serial-Board" The ones where the PCB is barely bigger than the SMD chip are the ones I'm talking about. So small, you can fit one inside almost anything. So cheap, it's hardly worth making one yourself. It's definitely the gadget not receiving, rather than the RS232 source not sending? I'm just wondering if the source is expecting to see hardware or software handshaking before it will send? You may just need to strap two or three of the pins together inside the 'D' plug which is plugged into the USB-RS232 lead. Last edited by SiriusHardware; 26th Apr 2020 at 6:48 pm.