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Hi Ive been trying to achieve a "true" RS232 in BX01, using a MAX233, but I haven't had any success. To test the BX01 with Max233, I run the sample Serial_Number using Com2 and the BasicX Development System V2.0. Using the J9 output in the (old) development board and a crossed RX-TX cable to the PC Com1, the sample runs OK. When I insert the MAX233 (connected as below), I receive a serial error (or nothing). I also tried a non crossed cable with the same result. I tried MAX232 with capacitors with the same results. MAX233 connections: J9 TX ----------- MAX233 2 T1in J9 RX ----------- MAX233 3 R1out J9 ground ----------- MAX233 9 Gnd MAX233 6 Gnd ----------- MAX233 9 Gnd MAX233 9 Gnd ----------- 0 VDC MAX233 7 Vcc ----------- +5 VDC MAX233 11 C2+ ----------- MAX233 15 C2+ MAX233 12 V- ----------- MAX233 17 V- MAX233 10 Cs- ----------- MAX233 16 C2- MAX233 9 Gnd ----------- DB9 5 MAX233 4 R1in ----------- DB9 3 MAX233 5 T1out ----------- DB9 2 DB9 4 ----------- DB9 6 DB9 7 ----------- DB9 8 I'm probably doing something wrong, can somebody give me a light? Filippo |
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BX01 true RS232 with MAX233
Started by ●December 17, 2002
Reply by ●December 18, 20022002-12-18
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The output of the Atmel processor is at TTL levels. That is, a logic one is near +5 VDC and a logic zero is near ground. Netmedia then uses some transistors to invert these signals. This is cheating a bit as an RS232 logic one is less than -3 VDC and a logic zero is greater than +3 VDC. But, ground (rather than -3 VDC) seems to be adequate in most applications. In using J9, you are then inverting this signal again with your MAX2XX and thus your signal is inverted. Take a look at the schematic for the Board. You want to bypass the trasistors and connect your MAX2XX right at the RX and TX terminals of the processor. It appears there are some straps there. Remove the straps and you may be able to access these processor leads. Peter H Anderson, http://www.phanderson.com/basicx/ --- In , "basicxgroup <pardini@g...>" <pardini@g...> wrote: > Hi > > Ive been trying to achieve a "true" RS232 in BX01, using a MAX233, > but I haven't had any success. To test the BX01 with Max233, I run |
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Reply by ●December 18, 20022002-12-18
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Thank you Peter, I picked the signal at the J13 strap (Com2) and now all is working well. Thank you again for your help Filippo --- In , "pha555 <pha@p...>" <pha@p...> wrote: > > The output of the Atmel processor is at TTL levels. That is, a logic > one is near +5 VDC and a logic zero is near ground. > > Netmedia then uses some transistors to invert these signals. This is > cheating a bit as an RS232 logic one is less than -3 VDC and a logic > zero is greater than +3 VDC. But, ground (rather than -3 VDC) seems > to be adequate in most applications. > > In using J9, you are then inverting this signal again with your > MAX2XX and thus your signal is inverted. > > Take a look at the schematic for the Board. You want to bypass the > trasistors and connect your MAX2XX right at the RX and TX terminals > of the processor. It appears there are some straps there. Remove > the straps and you may be able to access these processor leads. > > Peter H Anderson, http://www.phanderson.com/basicx/ > > --- In , "basicxgroup <pardini@g...>" > <pardini@g...> wrote: > > Hi > > > > Ive been trying to achieve a "true" RS232 in BX01, using a MAX233, > > but I haven't had any success. To test the BX01 with Max233, I run |
