UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post

mikew8760 · 26th Apr 2020, 5:52 pm

The 28c16's were just the job, and programmed fine on my MiniPro programmer. I have been spending some time on other projects, so have just returned to the Maplin SBC.
I have given up on the Nicolet NICE. It's a dinky little piece of kit, but something has happened to it during the umpty years in storage, seems like a poor connection, but I cannot find any such.
So, I dusted off my 40 year old Microtek Z80 MICE, plugged it in and, amazingly it works! However, as usual, there is a snag. The comms is RS232, intended for a dumb terminal. I wish to use it with, say TeraTerm or PuTTY via USB, but the MICE is sufficiently old to expect 'true' RS232, with +/- 12v signalling. Of course there are myriad so-called USB to RS232 adapters, but all seem to be TTL signal levels - the MICE simply refuses to talk to such low-life devices. I suppose I could modify the MICE circuitry, it uses 4188 and 4189's, but I don't really wish to go down that rabbit hole.
So, how to acquire a USB to pukka RS232 adapter? I did have one, which had a Sipex chip to create the +/- 12V, but Sod's Law, the Rx channel don't work!
Does any know of a cheap adapter that will fill the bill? At the moment I'm considered making up a custom jobbie, with a couple of joule thieves to obtain the 12v. Again I could buy a MAX232 chip, (or even those adapters on ebay that also offer RS485, which are expensive and which I don't need) but where's the fun in that?

26th Apr 2020, 5:52 pm	#20
mikew8760 Triode Join Date: Mar 2020 Location: Bristol, UK. Posts: 18	Re: Maplin Z80 SBC The 28c16's were just the job, and programmed fine on my MiniPro programmer. I have been spending some time on other projects, so have just returned to the Maplin SBC. I have given up on the Nicolet NICE. It's a dinky little piece of kit, but something has happened to it during the umpty years in storage, seems like a poor connection, but I cannot find any such. So, I dusted off my 40 year old Microtek Z80 MICE, plugged it in and, amazingly it works! However, as usual, there is a snag. The comms is RS232, intended for a dumb terminal. I wish to use it with, say TeraTerm or PuTTY via USB, but the MICE is sufficiently old to expect 'true' RS232, with +/- 12v signalling. Of course there are myriad so-called USB to RS232 adapters, but all seem to be TTL signal levels - the MICE simply refuses to talk to such low-life devices. I suppose I could modify the MICE circuitry, it uses 4188 and 4189's, but I don't really wish to go down that rabbit hole. So, how to acquire a USB to pukka RS232 adapter? I did have one, which had a Sipex chip to create the +/- 12V, but Sod's Law, the Rx channel don't work! Does any know of a cheap adapter that will fill the bill? At the moment I'm considered making up a custom jobbie, with a couple of joule thieves to obtain the 12v. Again I could buy a MAX232 chip, (or even those adapters on ebay that also offer RS485, which are expensive and which I don't need) but where's the fun in that?