Ashley Roll has put together a really nice little unit here. Leave off the
MAX232 and keep these handy for the few times you need true RS232! Plugs
into any 0.1" header to connect to your circuit. Perfect for
the BASIC Stamp or other microcontroller appications.
Brady Palmquist says: "James...got your RS232/TTL cable today. FAST! And
it looks great. Will work great for programming radios. Thanks VERY much."
Erik Hanson reports that with a little modification, the RLC-1 can be used
to talk directly to monitors such as his Sony Trinitron GDM-5402, more likely
found as an OEM (his was branded by Micron) and as a result, his dead monitor
is back up and running!
The little 4 pin connector on the back of the monitor is called an ECS port
and is for TTL serial data sent by the Sony DAS (Digital Alignment Software)
to control all aspects of the operation of the monitor. The RLC-1 must be
modified by re-arranging the pins in the socket to match those on the monitor.
The pinout of the connector is, from top to bottom:
The RLC-1 RS232 to 3-Volt or 5-Volt (CMOS/TTL) Level converter provides
a simple, low-cost and easy to use solution to interfacing a CMOS or TTL
based circuit to an RS232/EIA232 serial port.
The RLC-1 contains an internal circuit to provide the positive and negative
voltages needed for true RS232/EIA232 compatibility and to convert these
voltages back to logic levels.
It is particularly suited to micro-controller applications; for instance
the PIC or ATMEL families of devices and products using these.
The RLC-1 is built into a small DB9 backshell with a short (10cm or 4") lead
terminating in a standard 0.1" (2.54mm) Molex KK-series 6 pin connector.
The connector is used to provide power to the converter and deliver the Serial
data signals to the attached circuit.
Its small size and convenience make it ideal for prototype or one-off systems,
eliminating the need to design and debug extra level shifting circuits. It
is also useful for circuits that need periodic connection to a host like
dataloggers where a single converter can be used with many products, reducing
the parts count and therefore cost for the individual units.
Logic Level Pin Assignments
Power supply to the RLC-1. 3 to 5 Volts.
Ground Connection (0V).
Data Out (TX)
Data sent from the logic level device to the RS232 device.
Data In (RX)
Data sent from the RS232 device to the logic level device.
Request to Send signal sent from the RS232 device to the
logic level device to indicate it wishes to transmit data. This signal is
Clear to Send signal sent from the logic level device to
the RS232 device indicating that it can begin sending data. This signal is
Logic Level Interface
The logic level (CMOS and TTL compatible) interface is a Molex KK Series,
locking and polarised 6 pin crimp terminal housing. A compatible header for
these connectors should be available from most electronics stores, alternatively
a 0.1" (2.54mm) universal header could be used.
Note that the logic level interface is not isolated from the RS232 level
interface and they share a common Ground.
The RLC-1 is build into a DB9 Backshell and comes with a female DB9 connector.
The DB9 RS232 connector is wire as a standard "Null Modem"; DTR, DSR and
CD are permanently wired together but the RTS and CTS signals are provided
to the 5-Volt interface and must be connected together if not used in the
Vcc Power Supply Current
No Load, TA = 25 Deg C
Logic Level Input Threshold Low
Logic Level Input Threshold High
Logic Level Output Voltage Low
Iout = 1.6mA (to Vcc)
Logic Level Output Voltage High
Iout = 1mA (to Gnd)
Vcc = 5V +/-10%, TA = -40 to 85 Deg C, unless otherwise
specified. Typical Values are referred to TA = 25 Deg C.
Absolute Maximum Ratings:
Absolute Maximum Ratings are those values beyond which damage to the device
may occur. Functional operation under these conditions is not to be implied.
Unit Power Supply
-0.3 to 6
Relative to Ground
Input Voltage on Data Out Connection
-0.3 to (Vcc +0.3)
Relative to Ground
Output Voltage on Data In Connection
-0.3 to (Vcc +0.3)
Relative to Ground
Storage Temperature Range
-55 to +125
Digital Nemesis Pty Ltd makes a single standard unit, but is able to
adapt them as needed. Note that a minimum order quantity will apply for
non-standard configurations. For more information, please contact
sales at digitalnemesis.com.
The following are some of the available options: (all units now support 3
Volt as well as 5 Volt operation)
Rugged All Metal Backshell
Bare Leads for Logic Level Interface
Custom Connector for Logic Level Interface
RTS and CTS internally connected and a 4 Pin connector for the Logic Level
Arthur asks: "Does the RCL invert the Pin-3 data out signal?" James Newton
answers: "Yes, the signal is inverted in terms of electrical polarity.
e.g. a TTL low will generate a positive voltage on the TX output pin, a TTL
high will generate a negative TX. But the other possible correct answer is
No, the signal is not inverted in terms of logic. In the
RS232 standard, a low electrical level
(3 to 15 volts) is defined as a logic 1, or 'on' or 'high'
and is referred to as 'marking.' So a TTL high, will generate an RS232 high.
"On the page http://www.piclist.com/techref/io/serial/RCL1.htm, it starts
with "RCL" and becomes "RLC" throughout the rest of description. Yep, I know:
Picky, Picky, Picky!!! Thanks for an interesting and useful site."
+James Newton answers: "Oops."
with larger components. Does not include a cable. 5 Volt operation only.
As of 2006/08/03 the cost was $10 for the PCB only, $14 for the kit and $26
A&T. If you don't mind the size and want to save $5 in return for building
the kit, this is a good option.
Converter Cable. Physically larger than the RLC-1. Used to sell
a version that was not a true MAX232, but the current version seems like
a good product. From Canada, so expect shipping and customs delays. Priced
at $16 plus $11 express shipping to US (5 to 7 business days advertised)
for a total price of $27. Compare with our $21 + $6 for 2-4 day Priority
Mail shipping. The price is the same, the shipping is faster. Read the ebay
comments: Many times shipping is fast, but you may be the one that gets held
up in customs. "Product works great, but it took over three weeks for me
to receive it (USA)." kielziz( 5 ) Jun-01-06 08:21 "Works as
described. Shipping is a little slow." asylumboy( 4 ) Jun-01-06 08:10 and
so on. In the end, the same thing costs less in Canada, but more to ship
to the USA. I have offered to resell this product in the USA, but he is
apparently not interested.