Differences

This shows you the differences between two versions of the page.

--- electronics:thermoprinter [2017/10/25 08:05] – dmmedia
+++ electronics:thermoprinter [2020/04/02 20:33] (current) – [02.04.2020] dmmedia
@@ Line 26: / Line 26: @@
 ===== Plans =====
-  * Write firmware to print predefined lines
   * Attach assembled circuits to print head and to eval board
   * Test printing
@@ Line 49: / Line 48: @@
     * Should be interrupt based (to allow time for calculations, data sending to the printer head and printing)
     * Should follow datasheet guide on printing start sequence (pull paper, then push to allow more or less constant speed printing)
+  * Write firmware to print predefined lines
   * Attach stepper motor driver to motor and eval board
   * Test assembled circuits with oscilloscope and compare with simulation
@@ Line 255: / Line 255: @@
 ==== 25.10.2017 ====
   * Selected and ordered non-BLE bluetooth module HC-05 and BK3231. BK3231 is cheaper and has better organized AT command communication, but it has slave only firmware. On the other hand HC-05 is a master/slave programmaticaly selectable unit, but AT communication is a bit tricky. There is also a possibility to change the firmware on a HC-05 modules to a commercial grade RN42 module firmware.
+  * Some more information on the BT modules:
+    * http://lobotryasy.net/bluetooth_spp_c.php
+    * http://radiokot.ru/circuit/digital/pcmod/39/
+    * http://www.instructables.com/id/3-Bluetooth-HID-Module-HC05-With-RN42-Firmware/
+    * http://www.instructables.com/id/Upgrade-Your-3-Bluetooth-Module-to-Have-HID-Firmwa/
+  * Tested battery voltage switch circuit. Outcome shows, that it works as expected:
+{{:electronics:vhefb6v0.png?nolink|VH enable with feedback 6.0V}} {{:electronics:vhefb8v4.png?nolink|VH enable with feedback 8.4V}}
+==== 5.11.2017 ====
+  * Tested battery voltage monitor circuit and overheat monitor circuit. As designed, battery voltage monitor trips when battery voltage declines below 6.0 V. Temperature monitor circuit trips at voltage level below 1.25 V, which corresponds to 65 C for NTC thermistor integrated into thermoprinter head.
+{{:electronics:bcwi.png?nolink|Battery voltage monitor trips at 6.0 V}} {{:electronics:traps.png?nolink|Overheat protection trips at 1.25 V corresponding to 65 C}}
+==== 12.11.2017 ====
+  * Received HC-05 Bluetooth transceivers:
+{{:electronics:img_1329.jpg?nolink|}}
+  * Published firmware on GitHub: https://github.com/dmmedia/Thermoprinter
+  * Firmware framework borrowed from [[https://github.com/MarlinFirmware/Marlin|Marlin 3D printers firmware]].
+  * Conversion from AVR to STM32 and adapting for thermoprinter is in progress (removing more than 1 stepper motor support, replacing analogue sensors and replacing endstops with bistate sensors)
+==== 21.11.2017 ====
+  * Received SPP-C Bluetooth transceivers
+  * Tested both HC-05 and SPP-C modules. HC-05 modules need to be powered on in special sequence to boot into AT command mode, while SPP-C modules are always in AT mode, while not connected to other Bluetooth device. Both modules do not require hardware flow control. Many android software applications support traditional Bluetooth serial communication.
+  * Firmware code is mostly ported from AVR to STM32 platform and unneeded functionality removed. At the moment ADC code left partially ported.
+==== 08.03.2018 ====
+  * Counting printable bits to optimize the number of simultaneously driven 64-bit blocks turned out to be a combinatorial task or [[https://en.wikipedia.org/wiki/Partition_problem|Partition problem]]. More specifically a [[https://en.wikipedia.org/wiki/Bin_packing_problem|Bin packing problem]]. Generally speaking, the resulting count of sums of simultaneously driven blocks will be not more than optimal count plus 2 if I would use First fit decreasing or Best fit decreasing algorithms.
+  * Counting bits themselves turned to be another well-known problem named [[https://en.wikipedia.org/wiki/Hamming_weight|Hamming weight]]. Need to check whether STM32 has any special support for bit counting.
+==== 02.04.2020 ====
+  * Thought that porting Marlin 3D printer firmware was bad idea, since the functionality is totally different and Marlin implementation is not brilliant. Will start from scratch and implement stepper motor advance on user button press and hold. Motor will advance with the lowest speed described in the thermal head manual. Next step will add accelleration and deceleration.