Difference between revisions of "ER-301/Teletype Connection Rev7"
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Step 5: And solder like this:<br> | Step 5: And solder like this:<br> | ||
https://forum.orthogonaldevices.com/uploads/default/original/2X/0/0a3722da3150d3243fa63971b0b5cedc7da948cf.png | https://forum.orthogonaldevices.com/uploads/default/original/2X/0/0a3722da3150d3243fa63971b0b5cedc7da948cf.png | ||
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+ | Step 6: Check continuity between the right side of R62 and the RX/SDA pin of the UART connector. | ||
+ | [[File:continuity-with-RX-SDA.png|400px]] | ||
{{Pitfall | Do not use a [https://en.wikipedia.org/wiki/Desoldering#Desoldering_pump solder sucker] on this board. If you need to remove excess solder, please use copper braid.}} | {{Pitfall | Do not use a [https://en.wikipedia.org/wiki/Desoldering#Desoldering_pump solder sucker] on this board. If you need to remove excess solder, please use copper braid.}} |
Revision as of 02:03, 14 September 2018
The first few runs of the ER-301 did not have a dedicated i2c header. Instead users would perform a small hardware modification (described here) so that they could use the exposed UART header instead.
Connecting the Teletype to the ER-301
In a nutshell, i2c requires 2 communication lines (SCL and SDA) plus 1 ground line. So there are 3 pins on the Teletype that need to be connected with a custom cable to 3 pins on the ER-301.
Since these connection pins were originally meant for UART communication you will need to perform a simple hardware modification to your ER-301 in order to enable i2c communication. Please refer to the I2C Mod section below for further instructions. |
There are 5 pins extending parallel from underneath the ER-301 CPU board. You will only be using the top 3. You can also see that the 5 pins are labeled on the ER-301 silkscreen as TX, RX, GND, GND, and 5V. Connect like this:
- Teletype GND to ER-301 GND.
- Teletype SCL to ER-301 TX.
- Teletype SDA to ER-301 RX.
Required Hardware Modification
The goal of this hardware modification is to short out the diode labeled D3 on the red CPU board on the back of the ER-301. The diode's original purpose was to provide level-shifting for the RX pin of the UART port. Shorting out this diode allows for this pin to be used for the SCL (clock) pin of i2c.
Required tools:
- Soldering iron (ESD-safe, reliable temperature control) and solder (recommend no-clean flux)
- Short length of solid core wire (or waste lead from a through-hole resistor or LED or similar)
- needle-nose pliers (optional)
Step 1: Cut a 7mm piece of solid core wire or use part of a lead from a resistor or LED:
Step 2: Bend it around some needle-nose pliers:
Step 3: You should have a nice boxy U-shape like this:
Step 4: Place around diode D3 like this with the bottom of the U oriented towards the bottom of the board so that we do not short resistor R62:
Step 5: And solder like this:
Step 6: Check continuity between the right side of R62 and the RX/SDA pin of the UART connector.
Do not use a solder sucker on this board. If you need to remove excess solder, please use copper braid. |