Teensy LC/3.2 In-System-Programming Adapter
This adapter board allows a Teensy LC or Teensy 3.2 to program Atmel ISP-compatible chips without a boot-loader on the target device. It also provides voltage level translation, allowing programming of 3.3V and 5V devices. A jumper block allows the power pin of the ISP connection to connected to the 3.3V regulator of the Teensy, the 5V USB supply voltage, or disconnected in the case of a self powered device.
Shown here is a 3D rendering of version 2.1 of the circuit board. Connector ISP1 provides connection to the SPI bus along with power and ground (a typical ISP header). Connector ISP2 provides access to the second SPI controller on the Teensy LC, but it is not available on the Teensy 3.2. Both support 3.3V level UARTs #1 and #3 on the ISP2 connector if the Teensy is reconfigured as such.
Assembly of the board by hand proved problematic due to the small pitch of the voltage translator chips. Two version 2.2 boards have been assembled, one with chips for both connectors, one with a chip for only ISP1. The second board had to have its solder connections touched up in spots, but has now been tested working. The first one requires further repairs.